diff --git a/README.md b/README.md
index 92a88255..22a41cf6 100644
--- a/README.md
+++ b/README.md
@@ -91,10 +91,22 @@ RPC_URL=<YOUR_RPC>
 NEXT_PUBLIC_TURNKEY_API_BASE_URL="https://api.turnkey.com"
 NEXT_PUBLIC_RPID="localhost"
 NEXT_PUBLIC_GA_API=<YOUR_ACCOUNTS_API_URL>
+
+# Vehicle templates. Both are server-only -- no NEXT_PUBLIC_ prefix, ever.
+DEFINITIONS_WRITE_TOKEN=<WRITE_TOKEN_FOR_DEFINITIONS_WORKER>
+DIMO_CURATOR_ADDRESSES=<COMMA_SEPARATED_0X_ADDRESSES>
 ```
 
 Make sure that the `NEXT_PUBLIC_GA_API` maps to your [Accounts API](https://github.com/DIMO-Network/accounts/tree/main) deployment URL.
 
+`DEFINITIONS_WRITE_TOKEN` is the bearer token for `PUT /t/:id` on
+[definitions-worker](https://github.com/DIMO-Network/definitions-worker). It is
+read only by `src/services/definitions.ts`, which throws if it is ever evaluated
+in a browser — the token must never reach a client bundle.
+`DIMO_CURATOR_ADDRESSES` lists the addresses allowed to set
+`hardwareTemplateId`, which decides what hardware ships and is never open to
+contributors.
+
 3. Install the dependencies:
 
 ```bash
diff --git a/__tests__/unit/app/templateRoute.test.ts b/__tests__/unit/app/templateRoute.test.ts
new file mode 100644
index 00000000..3f5e03b5
--- /dev/null
+++ b/__tests__/unit/app/templateRoute.test.ts
@@ -0,0 +1,174 @@
+/**
+ * @jest-environment node
+ */
+import { GET, PUT } from '@/app/api/templates/[id]/route';
+import { NextRequest } from 'next/server';
+
+jest.mock('@/services/definitions');
+jest.mock('@/services/templateEntitlement', () => ({
+  ...jest.requireActual('@/services/templateEntitlement'),
+  resolveCaller: jest.fn(),
+  countMintedVehicles: jest.fn().mockResolvedValue(0),
+  manufacturerOwner: jest.fn().mockResolvedValue(null),
+  curatorAddresses: jest.fn().mockReturnValue([]),
+}));
+
+import { fetchTemplate, fetchVocabulary, publishTemplate } from '@/services/definitions';
+import {
+  resolveCaller,
+  countMintedVehicles,
+  curatorAddresses,
+} from '@/services/templateEntitlement';
+
+const CALLER = '0x1111111111111111111111111111111111111111';
+const params = { params: Promise.resolve({ id: 'toyota_camry_2020' }) };
+
+const body = (over: Record<string, unknown> = {}) => ({
+  id: 'toyota_camry_2020',
+  deviceType: 'vehicle',
+  manufacturer: { slug: 'toyota', name: 'Toyota' },
+  model: 'Camry',
+  year: 2020,
+  attributes: {},
+  trims: [{ name: 'LE', attributes: {} }],
+  ...over,
+});
+
+const put = (payload: unknown, headers: Record<string, string> = {}) =>
+  new NextRequest('https://console.test/api/templates/toyota_camry_2020', {
+    method: 'PUT',
+    headers: { 'content-type': 'application/json', ...headers },
+    body: JSON.stringify(payload),
+  });
+
+const stored = { ...body(), version: 3, author: CALLER, createdAt: 'x', updatedAt: 'y' };
+
+describe('PUT /api/templates/[id]', () => {
+  beforeEach(() => {
+    (resolveCaller as jest.Mock).mockResolvedValue({ address: CALLER, email: 'a@b.c' });
+    (fetchTemplate as jest.Mock).mockResolvedValue(stored);
+    (publishTemplate as jest.Mock).mockResolvedValue({
+      ok: true,
+      template: { ...stored, version: 4 },
+    });
+    (countMintedVehicles as jest.Mock).mockResolvedValue(0);
+    (curatorAddresses as jest.Mock).mockReturnValue([]);
+  });
+
+  it('401s when there is no session', async () => {
+    (resolveCaller as jest.Mock).mockResolvedValue(null);
+    expect((await PUT(put(body()), params)).status).toBe(401);
+  });
+
+  it('stamps author from the session and never from the body', async () => {
+    await PUT(put(body(), { 'if-match': '"3"' }), params);
+    expect((publishTemplate as jest.Mock).mock.calls[0][1].author).toBe(CALLER);
+  });
+
+  it('rejects a body that tries to name its own author or version, rather than stripping it quietly', async () => {
+    for (const field of ['author', 'version', 'createdAt', 'updatedAt']) {
+      const resp = await PUT(
+        put(body({ [field]: field === 'version' ? 9 : 'x' })),
+        params,
+      );
+      expect(resp.status).toBe(400);
+      expect((await resp.json()).error).toContain(field);
+    }
+  });
+
+  it('requires If-Match when the template already exists', async () => {
+    const resp = await PUT(put(body()), params);
+    expect(resp.status).toBe(428);
+  });
+
+  it('forwards the client If-Match rather than the version it just read', async () => {
+    // The freshly-read version would silently rebase a stale editor onto
+    // whatever landed while it was open. The client's own version is the only
+    // one that means "this is what I edited".
+    await PUT(put(body(), { 'if-match': '"2"' }), params);
+    expect((publishTemplate as jest.Mock).mock.calls[0][2]).toEqual({
+      kind: 'update',
+      version: 2,
+    });
+  });
+
+  it('sends If-None-Match on a create', async () => {
+    (fetchTemplate as jest.Mock).mockResolvedValue(null);
+    await PUT(put(body()), params);
+    expect((publishTemplate as jest.Mock).mock.calls[0][2]).toEqual({ kind: 'create' });
+  });
+
+  it('403s a caller who needs a proposal, and names the count', async () => {
+    (countMintedVehicles as jest.Mock).mockResolvedValue(4212);
+    const resp = await PUT(put(body(), { 'if-match': '"3"' }), params);
+    expect(resp.status).toBe(403);
+    expect((await resp.json()).entitlement).toMatchObject({
+      kind: 'proposal-required',
+      mintedVehicles: 4212,
+    });
+    expect(publishTemplate).not.toHaveBeenCalled();
+  });
+
+  it('403s a hardwareTemplateId change from a non-curator, at every tier', async () => {
+    const resp = await PUT(
+      put(body({ hardwareTemplateId: '999' }), { 'if-match': '"3"' }),
+      params,
+    );
+    expect(resp.status).toBe(403);
+    expect((await resp.json()).error).toContain('hardwareTemplateId');
+    expect(publishTemplate).not.toHaveBeenCalled();
+  });
+
+  it('lets a curator set hardwareTemplateId', async () => {
+    (curatorAddresses as jest.Mock).mockReturnValue([CALLER.toLowerCase()]);
+    const resp = await PUT(
+      put(body({ hardwareTemplateId: '999' }), { 'if-match': '"3"' }),
+      params,
+    );
+    expect(resp.status).toBe(200);
+  });
+
+  it('passes the worker validation errors through unchanged', async () => {
+    (publishTemplate as jest.Mock).mockResolvedValue({
+      ok: false,
+      kind: 'validation',
+      errors: ['template: unknown attribute "nope"'],
+    });
+    const resp = await PUT(put(body(), { 'if-match': '"3"' }), params);
+    expect(resp.status).toBe(422);
+    expect((await resp.json()).errors).toEqual(['template: unknown attribute "nope"']);
+  });
+
+  it('turns a worker 412 into a 409 carrying the version to rebase onto', async () => {
+    (publishTemplate as jest.Mock).mockResolvedValue({
+      ok: false,
+      kind: 'conflict',
+      expected: 3,
+      actual: 5,
+    });
+    const resp = await PUT(put(body(), { 'if-match': '"3"' }), params);
+    expect(resp.status).toBe(409);
+    expect(await resp.json()).toMatchObject({ conflict: { expected: 3, actual: 5 } });
+  });
+});
+
+describe('GET /api/templates/[id]', () => {
+  it('returns the template, the live vocabulary and the caller entitlement in one payload', async () => {
+    (resolveCaller as jest.Mock).mockResolvedValue({ address: CALLER, email: 'a@b.c' });
+    (fetchTemplate as jest.Mock).mockResolvedValue(stored);
+    (fetchVocabulary as jest.Mock).mockResolvedValue({
+      id: 'vehicle',
+      name: 'Vehicle',
+      attributes: [],
+    });
+    const json = await (
+      await GET(
+        new NextRequest('https://console.test/api/templates/toyota_camry_2020'),
+        params,
+      )
+    ).json();
+    expect(json.template.version).toBe(3);
+    expect(json.vocabulary.id).toBe('vehicle');
+    expect(json.entitlement.kind).toBe('author');
+  });
+});
diff --git a/__tests__/unit/app/templatesSearchRoute.test.ts b/__tests__/unit/app/templatesSearchRoute.test.ts
new file mode 100644
index 00000000..34c609f4
--- /dev/null
+++ b/__tests__/unit/app/templatesSearchRoute.test.ts
@@ -0,0 +1,97 @@
+/**
+ * @jest-environment node
+ *
+ * Route handlers run on the server and this one reaches @/services/definitions,
+ * which refuses to load where `window` exists.
+ */
+import { GET } from '@/app/api/templates/route';
+import { NextRequest } from 'next/server';
+
+jest.mock('@/services/definitions', () => ({
+  fetchTemplate: jest.fn(),
+}));
+import { fetchTemplate } from '@/services/definitions';
+
+const identityResponse = {
+  data: {
+    manufacturer: {
+      name: 'Toyota',
+      tokenId: 131,
+      deviceDefinitions: {
+        nodes: [
+          { deviceDefinitionId: 'toyota_camry_2020', model: 'Camry', year: 2020 },
+          { deviceDefinitionId: 'toyota_supra_2020', model: 'Supra', year: 2020 },
+        ],
+      },
+    },
+  },
+};
+
+const req = (qs: string) => new NextRequest(`https://console.test/api/templates?${qs}`);
+
+describe('GET /api/templates', () => {
+  beforeEach(() => {
+    global.fetch = jest.fn().mockResolvedValue({
+      ok: true,
+      json: async () => identityResponse,
+    }) as unknown as typeof fetch;
+  });
+
+  it('requires a make', async () => {
+    expect((await GET(req('model=Camry'))).status).toBe(400);
+  });
+
+  it('marks a definition with no template as missing rather than failing', async () => {
+    (fetchTemplate as jest.Mock)
+      .mockResolvedValueOnce({ id: 'toyota_camry_2020', version: 3, trims: [{}, {}] })
+      .mockResolvedValueOnce(null);
+    const body = await (await GET(req('make=Toyota&model=Camry&year=2020'))).json();
+    expect(body.results).toEqual([
+      {
+        id: 'toyota_camry_2020',
+        model: 'Camry',
+        year: 2020,
+        status: 'ok',
+        version: 3,
+        trims: 2,
+      },
+      { id: 'toyota_supra_2020', model: 'Supra', year: 2020, status: 'missing' },
+    ]);
+  });
+
+  it('marks an id the schema cannot accept, without asking the worker about it', async () => {
+    global.fetch = jest.fn().mockResolvedValue({
+      ok: true,
+      json: async () => ({
+        data: {
+          manufacturer: {
+            name: 'Subaru',
+            tokenId: 1,
+            deviceDefinitions: {
+              nodes: [
+                {
+                  deviceDefinitionId: 'subaru_tribeca-(ny/nj)_2008',
+                  model: 'Tribeca',
+                  year: 2008,
+                },
+              ],
+            },
+          },
+        },
+      }),
+    }) as unknown as typeof fetch;
+    (fetchTemplate as jest.Mock).mockClear();
+    const body = await (await GET(req('make=Subaru'))).json();
+    expect(body.results[0].status).toBe('invalid-id');
+    expect(fetchTemplate).not.toHaveBeenCalled();
+  });
+
+  it('reports an unknown manufacturer as null rather than an empty result set', async () => {
+    global.fetch = jest.fn().mockResolvedValue({
+      ok: true,
+      json: async () => ({ data: { manufacturer: null } }),
+    }) as unknown as typeof fetch;
+    const body = await (await GET(req('make=Nope'))).json();
+    expect(body).toEqual({ manufacturer: null, results: [] });
+  });
+});
diff --git a/__tests__/unit/services/definitions.test.ts b/__tests__/unit/services/definitions.test.ts
new file mode 100644
index 00000000..6a920dc2
--- /dev/null
+++ b/__tests__/unit/services/definitions.test.ts
@@ -0,0 +1,112 @@
+/**
+ * @jest-environment node
+ *
+ * services/definitions is server-only and throws when `window` exists, which is
+ * the guarantee that DEFINITIONS_WRITE_TOKEN cannot reach a browser bundle. The
+ * default jsdom environment therefore cannot load it at all -- see the
+ * "refuses to load in a browser" case below, which asserts exactly that.
+ */
+import { fetchTemplate, fetchVocabulary, publishTemplate } from '@/services/definitions';
+import type { TemplatePayload } from '@/types/template';
+
+const payload = {
+  id: 'toyota_camry_2020',
+  deviceType: 'vehicle',
+  manufacturer: { slug: 'toyota', name: 'Toyota' },
+  model: 'Camry',
+  year: 2020,
+  attributes: {},
+  trims: [{ name: 'LE', attributes: {} }],
+} as unknown as TemplatePayload;
+
+const mockFetch = (impl: jest.Mock) => {
+  global.fetch = impl as unknown as typeof fetch;
+  return impl;
+};
+
+describe('definitions service', () => {
+  it('returns null for a template that does not exist yet', async () => {
+    mockFetch(
+      jest.fn().mockResolvedValue({ ok: false, status: 404, json: async () => ({}) }),
+    );
+    expect(await fetchTemplate('ineos_grenadier_2024')).toBeNull();
+  });
+
+  it('sends If-None-Match on create and If-Match on update, and never the token to the body', async () => {
+    process.env.DEFINITIONS_WRITE_TOKEN = 'secret-token';
+    const f = mockFetch(
+      jest.fn().mockResolvedValue({
+        ok: true,
+        status: 200,
+        json: async () => ({ ...payload, version: 1 }),
+      }),
+    );
+
+    await publishTemplate('toyota_camry_2020', payload, { kind: 'create' });
+    expect(f.mock.calls[0][1].headers['If-None-Match']).toBe('*');
+    expect(f.mock.calls[0][1].headers.Authorization).toBe('Bearer secret-token');
+    expect(f.mock.calls[0][1].body).not.toContain('secret-token');
+
+    await publishTemplate('toyota_camry_2020', payload, { kind: 'update', version: 7 });
+    expect(f.mock.calls[1][1].headers['If-Match']).toBe('"7"');
+  });
+
+  it('maps 422 to validation errors and 412 to a conflict', async () => {
+    mockFetch(
+      jest.fn().mockResolvedValue({
+        ok: false,
+        status: 422,
+        json: async () => ({ errors: ['template: unknown attribute "nope"'] }),
+      }),
+    );
+    expect(
+      await publishTemplate('toyota_camry_2020', payload, { kind: 'create' }),
+    ).toEqual({
+      ok: false,
+      kind: 'validation',
+      errors: ['template: unknown attribute "nope"'],
+    });
+
+    mockFetch(
+      jest.fn().mockResolvedValue({
+        ok: false,
+        status: 412,
+        json: async () => ({
+          error: 'expected version 6 but the current version is 7',
+          expected: 6,
+          actual: 7,
+        }),
+      }),
+    );
+    expect(
+      await publishTemplate('toyota_camry_2020', payload, { kind: 'update', version: 6 }),
+    ).toEqual({ ok: false, kind: 'conflict', expected: 6, actual: 7 });
+  });
+
+  it('refuses a payload over the worker 64KB cap before spending a request', async () => {
+    const f = mockFetch(jest.fn());
+    const fat = {
+      ...payload,
+      trims: Array.from({ length: 4000 }, (_, i) => ({ name: `T${i}`, attributes: {} })),
+    };
+    const result = await publishTemplate(
+      'toyota_camry_2020',
+      fat as unknown as TemplatePayload,
+      { kind: 'create' },
+    );
+    expect(result).toMatchObject({ ok: false, kind: 'too-large' });
+    expect(f).not.toHaveBeenCalled();
+  });
+
+  it('fetches the vocabulary from the worker, not from a vendored copy', async () => {
+    const f = mockFetch(
+      jest.fn().mockResolvedValue({
+        ok: true,
+        status: 200,
+        json: async () => ({ id: 'vehicle', name: 'Vehicle', attributes: [] }),
+      }),
+    );
+    await fetchVocabulary();
+    expect(f.mock.calls[0][0]).toContain('/schema/device-type-vehicle.json');
+  });
+});
diff --git a/__tests__/unit/services/definitionsServerOnly.test.ts b/__tests__/unit/services/definitionsServerOnly.test.ts
new file mode 100644
index 00000000..bd9e6ea3
--- /dev/null
+++ b/__tests__/unit/services/definitionsServerOnly.test.ts
@@ -0,0 +1,11 @@
+/**
+ * Runs in jsdom (the project default) on purpose: importing the server-only
+ * module where `window` exists must fail. This is gate 1's guarantee, and a
+ * convention would not be testable.
+ */
+describe('services/definitions in a browser', () => {
+  it('refuses to load', async () => {
+    const { fetchTemplate } = await import('@/services/definitions');
+    await expect(fetchTemplate('toyota_camry_2020')).rejects.toThrow(/server-only/);
+  });
+});
diff --git a/__tests__/unit/services/templateEntitlement.test.ts b/__tests__/unit/services/templateEntitlement.test.ts
new file mode 100644
index 00000000..d2922932
--- /dev/null
+++ b/__tests__/unit/services/templateEntitlement.test.ts
@@ -0,0 +1,119 @@
+/**
+ * @jest-environment node
+ */
+import { resolveEntitlement } from '@/services/templateEntitlement';
+import type { Template } from '@/types/template';
+
+const CALLER = '0x1111111111111111111111111111111111111111';
+const OTHER = '0x2222222222222222222222222222222222222222';
+const CURATOR = '0x3333333333333333333333333333333333333333';
+
+const template = (over: Partial<Template> = {}) =>
+  ({
+    id: 'toyota_camry_2020',
+    deviceType: 'vehicle',
+    manufacturer: { slug: 'toyota', name: 'Toyota', tokenId: 131 },
+    model: 'Camry',
+    year: 2020,
+    attributes: {},
+    trims: [{ name: 'LE', attributes: {} }],
+    version: 3,
+    createdAt: '2026-08-01T00:00:00.000Z',
+    updatedAt: '2026-08-01T00:00:00.000Z',
+    ...over,
+  }) as Template;
+
+const deps = (minted: number, owner: string | null) => ({
+  countMintedVehicles: jest.fn().mockResolvedValue(minted),
+  manufacturerOwner: jest.fn().mockResolvedValue(owner ? { owner, tokenId: 131 } : null),
+  curators: [CURATOR],
+});
+
+describe('resolveEntitlement', () => {
+  it('lets any signed-in account create a template that does not exist', async () => {
+    expect(
+      await resolveEntitlement({ caller: CALLER, template: null, ...deps(0, OTHER) }),
+    ).toMatchObject({
+      kind: 'create',
+      canPublish: true,
+      canSetHardwareTemplateId: false,
+    });
+  });
+
+  it('lets the author edit an unreferenced template', async () => {
+    const e = await resolveEntitlement({
+      caller: CALLER,
+      template: template({ author: CALLER }),
+      ...deps(0, OTHER),
+    });
+    expect(e).toMatchObject({ kind: 'author', canPublish: true });
+  });
+
+  it('treats an unauthored backfill template as unowned while nothing references it', async () => {
+    const e = await resolveEntitlement({
+      caller: CALLER,
+      template: template(),
+      ...deps(0, OTHER),
+    });
+    expect(e).toMatchObject({ kind: 'author', canPublish: true });
+  });
+
+  it('requires a proposal to edit somebody else unreferenced template', async () => {
+    const e = await resolveEntitlement({
+      caller: CALLER,
+      template: template({ author: OTHER }),
+      ...deps(0, OTHER),
+    });
+    expect(e).toMatchObject({ kind: 'proposal-required', canPublish: false });
+  });
+
+  it('lets the manufacturer NFT holder edit a template with minted vehicles', async () => {
+    const e = await resolveEntitlement({
+      caller: CALLER,
+      template: template({ author: OTHER }),
+      ...deps(4212, CALLER.toUpperCase()),
+    });
+    expect(e).toMatchObject({
+      kind: 'manufacturer',
+      canPublish: true,
+      mintedVehicles: 4212,
+    });
+  });
+
+  it('requires a proposal for everyone else once vehicles are minted, and says how many', async () => {
+    const e = await resolveEntitlement({
+      caller: CALLER,
+      template: template({ author: CALLER }),
+      ...deps(4212, OTHER),
+    });
+    expect(e).toMatchObject({
+      kind: 'proposal-required',
+      canPublish: false,
+      mintedVehicles: 4212,
+    });
+  });
+
+  it('gives a curator publish rights and the only hardwareTemplateId rights', async () => {
+    const e = await resolveEntitlement({
+      caller: CURATOR,
+      template: template({ author: OTHER }),
+      ...deps(4212, OTHER),
+    });
+    expect(e).toMatchObject({
+      kind: 'curator',
+      canPublish: true,
+      canSetHardwareTemplateId: true,
+    });
+  });
+
+  it('never grants hardwareTemplateId rights to a non-curator, at any tier', async () => {
+    for (const t of [null, template({ author: CALLER })]) {
+      const e = await resolveEntitlement({
+        caller: CALLER,
+        template: t,
+        ...deps(0, CALLER),
+      });
+      expect(e.canSetHardwareTemplateId).toBe(false);
+    }
+  });
+});
diff --git a/__tests__/unit/types/generatedTemplateTypes.test.ts b/__tests__/unit/types/generatedTemplateTypes.test.ts
new file mode 100644
index 00000000..549bc763
--- /dev/null
+++ b/__tests__/unit/types/generatedTemplateTypes.test.ts
@@ -0,0 +1,36 @@
+import { execFileSync } from 'node:child_process';
+import { readFileSync, writeFileSync } from 'node:fs';
+import path from 'node:path';
+
+// The template contract has three generated mirrors (this one, the worker's TS,
+// dd-api's Go). Generation without a guard is the same defect as hand-writing
+// them, one step removed: the copies still drift, and nothing says so. This
+// runs the real check `npm run build` runs, so the two cannot disagree.
+const ROOT = path.resolve(__dirname, '../../..');
+const GENERATED = path.join(ROOT, 'src/types/generated/template.ts');
+
+const check = () =>
+  execFileSync('node', ['scripts/gen-template-types.mjs', '--check'], {
+    cwd: ROOT,
+    encoding: 'utf8',
+    stdio: 'pipe',
+  });
+
+describe('generated template types', () => {
+  it('are what the vendored schema produces right now', () => {
+    expect(() => check()).not.toThrow();
+  });
+
+  // Without this, the test above passes for a guard that can never fail --
+  // which is exactly the shape of defect this project keeps producing.
+  it('fail the check when the committed output is stale', () => {
+    const committed = readFileSync(GENERATED, 'utf8');
+    try {
+      writeFileSync(GENERATED, `${committed}\nexport type Drifted = true;\n`);
+      expect(() => check()).toThrow();
+    } finally {
+      writeFileSync(GENERATED, committed);
+    }
+    expect(readFileSync(GENERATED, 'utf8')).toBe(committed);
+  });
+});
diff --git a/docs/superpowers/plans/2026-08-28-console-template-editor.md b/docs/superpowers/plans/2026-08-28-console-template-editor.md
new file mode 100644
index 00000000..33438a9c
--- /dev/null
+++ b/docs/superpowers/plans/2026-08-28-console-template-editor.md
@@ -0,0 +1,5447 @@
+# Console Template Editor Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Ship a template editor in DIMO Developer Console that makes trim
+divergence visible and can safely publish a new template version, after closing
+the three write-path gates that do not exist yet.
+
+**Architecture:** Three layers. (1) `definitions-worker` gains a public
+`GET /schema/<file>` route, real compare-and-swap on writes, and generated TS
+types — the three prerequisites the handoff names. (2) Console gains a
+server-only route at `/api/templates/[id]` that holds `WRITE_TOKEN`, verifies
+the existing session cookie, stamps `author` from that session, resolves the
+caller's contribution tier against identity-api, and proxies to the worker with
+`If-Match`. (3) The browser gets a grid — trims as columns, attributes as rows,
+agreement muted and divergence at full contrast — driven by a pure,
+heavily-tested transformation module that never mutates a template in place.
+
+**Tech Stack:** Console — Next.js 15 App Router, React 18, TypeScript 5.9,
+Tailwind 3, Apollo Client (identity-api), Jest + React Testing Library.
+Worker — Cloudflare Workers, TypeScript, Vitest + `@cloudflare/vitest-pool-workers`
+(miniflare), R2.
+
+**Spec:**
+
+- `definitions-worker/docs/superpowers/specs/2026-08-27-open-trim-registry.md` — the registry design and the contribution model.
+- `~/workspace/HANDOFF-console-templates.md` — this feature's brief, the four gates, the design direction.
+- `~/workspace/VERIFY-trim-templates.md` — measured state, decisions taken, known-open items.
+- `definitions-worker/schema/` — the authoritative contract (`template.schema.json`, `device-type-vehicle.json`, `resolved.schema.json`, `examples/toyota_camry_2020.json`).
+
+---
+
+## Global Constraints
+
+Every task's requirements implicitly include this section.
+
+**Repos and branches**
+
+- Worker tasks (1–3): repo `~/workspace/definitions-worker`, new branch `template-cas` stacked on `trim-extraction` (HEAD `a762582`). Do not merge into `trim-extraction`; it is under review as PRs #1/#2/#3.
+- Console tasks (4–11): repo `~/workspace/dimo-developer-console`, new branch `template-editor` off `master` (HEAD `da1df4f`).
+- **No `Co-Authored-By` trailer and no Claude attribution in any commit message or PR body.** Both repos currently have zero such trailers; keep it that way.
+
+**The contract — rules the UI must honour, not just the API**
+
+- An attribute lives on the template **or** on a trim, never both.
+- Absent is not empty. Clearing a field _removes_ the attribute. `""` and `<nil>` are unrepresentable.
+- Values are typed. `fuel_tank_capacity_gal` is `15.8`, never `"15.800000"`.
+- Enum values come from that attribute's `options`. Never free text.
+- `hardwareTemplateId` is DIMO-only at every tier, is not a vehicle attribute, and sits outside `attributes`.
+- A multi-trim template may not contain a trim without an effective selector. Degenerate selectors (`vinPattern: ''`, `manufacturerCode: ['']`, `manufacturerCode: []`, `selectors: {}`) do not count as selectors.
+- `version`, `createdAt` and `updatedAt` are server-owned. Never send them; the worker rejects them as `unexpected top-level key "<name>"`.
+- `author` is server-stamped from the session. The browser never supplies it and never sees `WRITE_TOKEN`.
+- Request body cap is **64 KB** (`MAX_DOC_BYTES` in `definitions-worker/src/index.ts`); over it the worker returns 413 `{"error":"request body exceeds 64KB"}`.
+- Template id pattern: `^[a-z0-9][a-z0-9._&+-]*_[a-z0-9._&+-]+_[0-9]{4}$`, and the trailing year must equal the `year` field.
+
+**Console design system — verified values, use these and nothing else**
+
+|                         | Value                                                                                          | Source                                                                               |
+| ----------------------- | ---------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------ |
+| Page background         | `#000` (`bg-black`)                                                                            | `src/app/globals.css`: `body @apply bg-black`                                        |
+| Surfaces                | `bg-surface-default` `#141012` / `bg-surface-sunken` `#0A0508` / `bg-surface-raised` `#201C1E` | `tailwind.config.ts`                                                                 |
+| Input ground            | `bg-dark-grey-950` `#24292f`                                                                   | `tailwind.config.ts`                                                                 |
+| Accent                  | `text-primary-300` / `bg-primary-300` `#6aded5`                                                | `Button.css` `.primary-solid`                                                        |
+| Outline border          | `border-cta-default` `#322D2F`                                                                 | `tailwind.config.ts`                                                                 |
+| Error **fill**          | `bg-feedback-error` `#8E3231`                                                                  | `tailwind.config.ts`                                                                 |
+| Error **text on black** | `text-red-400` `#fe6b6b`                                                                       | `tailwind.config.ts`; `#8E3231` is a fill colour and is unreadable as text on `#000` |
+| Font                    | Universal Sans Display, local, **weights 525 and 900 only**                                    | `src/utils/font.ts`                                                                  |
+| Muting                  | white opacity (`text-white/50`, `text-white/40`, `text-white/25`)                              | there is no light weight; emphasis rides on opacity                                  |
+| Buttons                 | `<Button className="...">` — white pill, black text, `rounded-full h-10`                       | `src/components/Button/`                                                             |
+
+**Console conventions**
+
+- App Router only. Pages that touch wallet/session state are `'use client'`.
+- Page directory shape follows `src/app/webhooks/`: `page.tsx` + `layout.ts` (`export default AuthorizedLayout`) + a `<name>Page/View/View.tsx` + `create/` + `edit/`.
+- Tests live in `__tests__/unit/...` or colocated `__tests__/` next to the module (both exist; `src/app/app/list/components/VehicleSimulator/__tests__/` is the colocated precedent). Jest maps `@/` → `src/`.
+- `npm test`, `npm run compile` (typecheck), and `npm run lint` must all pass before every commit.
+- Server-only secrets never get a `NEXT_PUBLIC_` prefix.
+- `src/middleware.ts` already 401s any unauthenticated request to `/api/*` that is not under `UNPROTECTED_PATHS`. That is a first line, not the authorization; each route still resolves its own caller.
+
+**Scope boundary**
+This plan ships the tiers that publish **directly**: create, edit-your-own-unreferenced, and manufacturer-NFT-holder. The **proposal** tier (edit a referenced template you do not own → a curator merges) needs a proposal store the worker does not have; it is out of scope and gets its own plan. Where the caller is not entitled, the editor is read-only and says exactly why. A publish flow that cannot safely publish is worse than one that declines out loud.
+
+**Traps this plan carries, and where each is handled**
+
+| Trap (from the handoff)                                                     | Where                                                                                                                                                                    |
+| --------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
+| Templates may be attribute-free — 5,152 of the emitted set are              | Task 5 renders every vocabulary attribute as a row whether or not it is set, so the common empty state is the affordance for filling it in; Task 12 creates one that way |
+| 137 production ids fail the id schema (`subaru_tribeca-(ny/nj)_2008`)       | Task 8 shows them as `invalid-id` with the reason, and never asks the worker about them                                                                                  |
+| 668 definitions have no powertrain at all — missing is legitimate           | `—` in Task 7 means not set and is visually distinct from a value; nothing treats absence as an error                                                                    |
+| `GET /admin/history` is paged (`limit` 200 default, 500 max, `next` cursor) | No consumer in this plan reads it; recorded under "Not in this plan" so the follow-on carries the constraint                                                             |
+| `version`, `createdAt`, `updatedAt` are server-owned                        | `toPayload` (Task 5) strips them; the route refuses a body carrying them by name (Task 9)                                                                                |
+| 64 KB body cap                                                              | Checked in `publishTemplate` before a request is spent (Task 4)                                                                                                          |
+
+---
+
+## File Structure
+
+**`definitions-worker` (Tasks 1–3)**
+
+| File                                                     | Responsibility                                                                      |
+| -------------------------------------------------------- | ----------------------------------------------------------------------------------- |
+| `src/index.ts` (modify)                                  | add `GET /schema/<file>`; wire `If-Match` / `If-None-Match` on `PUT /t/:id`         |
+| `src/store.ts` (modify)                                  | `writeTemplate` takes `expectedVersion`; conditional R2 put; `VersionConflictError` |
+| `src/template.ts` (modify)                               | import generated types instead of declaring them                                    |
+| `schema/template.schema.json` (modify)                   | add `title` to `$defs` and `manufacturer` so generated type names are deterministic |
+| `schema/generated/template.ts` (create)                  | generated, committed, drift-checked                                                 |
+| `scripts/gen-types.mjs` (create)                         | the generator, with `--check` mode                                                  |
+| `test/store.test.ts`, `test/write-path.test.ts` (modify) | `FakeBucket.put` honours `onlyIf`                                                   |
+| `test/generated-types.test.mjs` (create)                 | fails when the committed types drift from the schema                                |
+| `test/integration/conditional-write.test.ts` (create)    | proves **real** R2 honours the conditional put                                      |
+
+**`dimo-developer-console` (Tasks 4–11)**
+
+| File                                                                        | Responsibility                                                                       |
+| --------------------------------------------------------------------------- | ------------------------------------------------------------------------------------ |
+| `src/config/default.ts`, `production.ts`, `preview.ts`, `index.ts` (modify) | `definitionsWorkerUrl`                                                               |
+| `scripts/gen-template-types.mjs` (create)                                   | fetch schema → `src/types/generated/template.ts`                                     |
+| `src/types/generated/template.ts` (create)                                  | generated, committed                                                                 |
+| `src/types/template.ts` (create)                                            | re-export + the hand-written vocabulary types the schema does not carry              |
+| `src/services/definitions.ts` (create)                                      | **server-only** worker client: read template, read vocabulary, write with `If-Match` |
+| `src/services/templateEntitlement.ts` (create)                              | **server-only** identity-api queries + tier resolution                               |
+| `src/utils/templateGrid.ts` (create)                                        | the pure model: grid, divergence, lift/push, edits, payload                          |
+| `src/utils/templateCoerce.ts` (create)                                      | typed coercion + the normalisation report                                            |
+| `src/utils/templateValidate.ts` (create)                                    | client-side mirror of the worker's validator                                         |
+| `src/app/api/templates/[id]/route.ts` (create)                              | GET bundle + PUT publish; holds `WRITE_TOKEN`                                        |
+| `src/components/TemplateEditor/TrimGrid/` (create)                          | the grid                                                                             |
+| `src/components/TemplateEditor/DivergenceRail/` (create)                    | per-attribute distinct count + Move to shared                                        |
+| `src/components/TemplateEditor/NormalisationPanel/` (create)                | what the editor changed that you did not type                                        |
+| `src/components/TemplateEditor/TrimSelectorEditor/` (create)                | selector editing + gate ④ state                                                      |
+| `src/app/templates/layout.ts`, `page.tsx`, `templatesPage/` (create)        | browse                                                                               |
+| `src/app/templates/[id]/page.tsx` + `components/` (create)                  | edit                                                                                 |
+| `src/app/templates/new/page.tsx` + `components/` (create)                   | create                                                                               |
+| `src/gql/` (regenerated)                                                    | via `npm run compile` after adding the new documents                                 |
+
+---
+
+# Phase 0 — the gates (repo: `definitions-worker`)
+
+Nothing in Phase 1 or 2 may be deployed until these three land. Do them first,
+in order. Start by branching:
+
+```bash
+cd ~/workspace/definitions-worker
+git checkout trim-extraction && git pull --ff-only 2>/dev/null || true
+git checkout -b template-cas
+npm test && npm run test:integration && npm run typecheck
+# baseline: 199 unit, 35 integration, typecheck clean
+```
+
+---
+
+### Task 1: Serve the contract from the worker
+
+Console needs `device-type-vehicle.json` at runtime — it is what makes the form
+schema-driven, and fetching it rather than vendoring it is what stops the form's
+vocabulary drifting from the vocabulary the validator applies. It needs
+`template.schema.json` at build time to generate types (Task 3, and Console
+Task 4). Neither is served today.
+
+**Files:**
+
+- Modify: `definitions-worker/src/index.ts`
+- Test: `definitions-worker/test/integration/worker.test.ts`
+
+**Interfaces:**
+
+- Consumes: nothing.
+- Produces: `GET /schema/template.schema.json`, `GET /schema/device-type-vehicle.json`, `GET /schema/resolved.schema.json` — public, no auth, `content-type: application/json`, `cache-control: public, max-age=300, stale-while-revalidate=3600`. Unknown name → 404 `{"error":"not found"}`.
+
+Cache is 300 s, not the 86,400 s templates get: a schema changes on deploy and
+there is no purge hook for it, and a stale vocabulary silently changes which
+options a contributor is offered. Five minutes of staleness is the ceiling that
+buys.
+
+- [ ] **Step 1: Write the failing integration test**
+
+Append to `test/integration/worker.test.ts`:
+
+```ts
+describe('GET /schema/<file>', () => {
+  it('serves the vocabulary and the template schema without auth', async () => {
+    const vocab = await SELF.fetch('https://w/schema/device-type-vehicle.json');
+    expect(vocab.status).toBe(200);
+    expect(vocab.headers.get('content-type')).toContain('application/json');
+    expect(vocab.headers.get('cache-control')).toBe(
+      'public, max-age=300, stale-while-revalidate=3600',
+    );
+    const doc = (await vocab.json()) as { id: string; attributes: { name: string }[] };
+    expect(doc.id).toBe('vehicle');
+    expect(doc.attributes.map((a) => a.name)).toContain('powertrain_type');
+
+    const schema = await SELF.fetch('https://w/schema/template.schema.json');
+    expect(schema.status).toBe(200);
+    expect(((await schema.json()) as { title: string }).title).toBe('Template');
+  });
+
+  it('404s an unknown schema name and never walks out of the map', async () => {
+    for (const name of ['nope.json', '../wrangler.toml', 'index.ts']) {
+      const resp = await SELF.fetch(`https://w/schema/${encodeURIComponent(name)}`);
+      expect(resp.status).toBe(404);
+    }
+  });
+});
+```
+
+- [ ] **Step 2: Run it and watch it fail**
+
+Run: `npm run test:integration`
+Expected: FAIL — `expected 404 to be 200`, because `/schema/...` falls through to the final `json({ error: 'not found' }, 404)`.
+
+- [ ] **Step 3: Implement the route**
+
+In `src/index.ts`, next to the existing `vehicleVocab` import:
+
+```ts
+import templateSchema from '../schema/template.schema.json';
+import resolvedSchema from '../schema/resolved.schema.json';
+```
+
+Below `const VEHICLE_VOCAB = ...`, add:
+
+```ts
+// The contract, served from the same deploy that enforces it. Console fetches
+// the vocabulary at runtime rather than vendoring a copy: a vendored copy can
+// offer a contributor an option this worker will reject, and that mismatch is
+// invisible until save. A fixed map, never a filesystem lookup -- there is no
+// filesystem here, and a name-derived path would be the only place in this
+// worker a caller could steer a read.
+const SCHEMAS: Record<string, unknown> = {
+  'template.schema.json': templateSchema,
+  'device-type-vehicle.json': vehicleVocab,
+  'resolved.schema.json': resolvedSchema,
+};
+
+// Shorter than DOC_CACHE by two orders of magnitude on purpose: a schema
+// changes with a deploy and nothing purges it, so this number is the window in
+// which a contributor can be shown a vocabulary the validator no longer uses.
+const SCHEMA_CACHE = 'public, max-age=300, stale-while-revalidate=3600';
+```
+
+And inside `fetch`, immediately after the `templateMatch` block:
+
+```ts
+const schemaMatch = path.match(/^\/schema\/([^/]+)$/);
+if (schemaMatch) {
+  if (req.method !== 'GET') return json({ error: 'method not allowed' }, 405);
+  const doc = SCHEMAS[decodeURIComponent(schemaMatch[1])];
+  if (doc === undefined) return json({ error: 'not found' }, 404);
+  return new Response(JSON.stringify(doc), {
+    status: 200,
+    headers: { 'content-type': 'application/json', 'cache-control': SCHEMA_CACHE },
+  });
+}
+```
+
+- [ ] **Step 4: Run the tests**
+
+Run: `npm run test:integration && npm test && npm run typecheck`
+Expected: PASS — 37 integration (35 + 2), 199 unit, typecheck clean.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add src/index.ts test/integration/worker.test.ts
+git commit -m "feat(worker): serve schema/ documents publicly
+
+Console needs the vehicle vocabulary at runtime to drive the editor form and
+the template schema at build time to generate types. Fetching beats vendoring:
+a vendored vocabulary can offer an option this worker rejects, and the
+mismatch is invisible until save."
+```
+
+---
+
+### Task 2: Compare-and-swap on write — gate ②
+
+`writeTemplate` probes forward for a free version number and writes it
+unconditionally. Two concurrent saves can probe to the same number and the
+second overwrites the first's _immutable_ version object. "Nothing is
+contended" was true while one backfill process wrote; the editor is what makes
+it false.
+
+The fix is a conditional put on the version key — R2's `onlyIf:
+{ etagDoesNotMatch: '*' }`, which returns `null` instead of writing when the
+key already exists (`R2Bucket.put` overload at
+`node_modules/@cloudflare/workers-types/index.d.ts:2476`). That is the actual
+compare-and-swap; the meta head check on top of it is what turns a lost update
+into a 412 the editor can show.
+
+Three modes, so the existing unconditional callers (import, backfill, dd-api)
+keep working unchanged:
+
+| `expectedVersion` | meaning                                                | route header       |
+| ----------------- | ------------------------------------------------------ | ------------------ |
+| `undefined`       | unconditional — probe forward, but still never clobber | none               |
+| `null`            | must not exist                                         | `If-None-Match: *` |
+| `n` (number)      | current head must be exactly `n`; write `n+1`          | `If-Match: "n"`    |
+
+**Files:**
+
+- Modify: `definitions-worker/src/store.ts:32-96` (`WriteOptions`, `writeTemplate`)
+- Modify: `definitions-worker/src/index.ts` (the `PUT` branch of `handleTemplateRequest`)
+- Test: `definitions-worker/test/store.test.ts`, `definitions-worker/test/write-path.test.ts`
+- Test: `definitions-worker/test/integration/conditional-write.test.ts` (create)
+
+**Interfaces:**
+
+- Consumes: `readMeta`, `versionKey`, `templateKey`, `metaKey`, `historyKey` from `src/store.ts`.
+- Produces:
+  - `WriteOptions { now: string; author?: string; expectedVersion?: number | null }`
+  - `class VersionConflictError extends Error { name = 'VersionConflictError'; expected: number | null; actual: number }`
+  - `PUT /t/:id` returns **412** `{ error, expected, actual }` on a precondition failure and **400** on a malformed `If-Match`.
+
+- [ ] **Step 1: Teach the fakes about `onlyIf`, then write the failing tests**
+
+First, in **both** `test/store.test.ts:9` and `test/write-path.test.ts:37`,
+replace `FakeBucket.put` with:
+
+```ts
+  // R2's real put returns null instead of writing when onlyIf fails. A fake
+  // that ignores onlyIf would pass every CAS test while proving nothing --
+  // which is this project's recurring failure shape, so the integration test
+  // below exercises the real binding as well.
+  async put(key: string, body: string, opts?: { onlyIf?: { etagDoesNotMatch?: string } }) {
+    if (opts?.onlyIf?.etagDoesNotMatch === '*' && this.store.has(key)) return null;
+    this.store.set(key, body);
+    return { etag: `e${++this.seq}` };
+  }
+```
+
+Then append to `test/store.test.ts`:
+
+```ts
+import { VersionConflictError } from '../src/store';
+
+describe('writeTemplate compare-and-swap', () => {
+  it('expectedVersion null creates, and refuses when the template already exists', async () => {
+    const e = env();
+    const first = await writeTemplate(e, body(), {
+      now: '2026-08-28T00:00:00.000Z',
+      expectedVersion: null,
+    });
+    expect(first.version).toBe(1);
+    await expect(
+      writeTemplate(e, body(), {
+        now: '2026-08-28T00:01:00.000Z',
+        expectedVersion: null,
+      }),
+    ).rejects.toMatchObject({ name: 'VersionConflictError', expected: null, actual: 1 });
+  });
+
+  it('expectedVersion n writes n+1 and refuses a stale n', async () => {
+    const e = env();
+    await writeTemplate(e, body(), { now: '2026-08-28T00:00:00.000Z' });
+    const second = await writeTemplate(e, body(), {
+      now: '2026-08-28T00:01:00.000Z',
+      expectedVersion: 1,
+    });
+    expect(second.version).toBe(2);
+    await expect(
+      writeTemplate(e, body(), { now: '2026-08-28T00:02:00.000Z', expectedVersion: 1 }),
+    ).rejects.toMatchObject({ name: 'VersionConflictError', expected: 1, actual: 2 });
+  });
+
+  it('a conditional write never overwrites an existing immutable version object', async () => {
+    const e = env();
+    await writeTemplate(e, body(), { now: '2026-08-28T00:00:00.000Z' });
+    const bucket = e.DEFS_BUCKET as unknown as { store: Map<string, string> };
+    // Simulate the loser of a race: meta still says head=1, but v/2 already
+    // landed from the winner. Probing forward would have written v/3 and left
+    // the head at a version nobody asked for; CAS must refuse instead.
+    bucket.store.set(
+      versionKey('toyota_camry_2020', 2),
+      JSON.stringify({ version: 2, winner: true }),
+    );
+    await expect(
+      writeTemplate(e, body(), { now: '2026-08-28T00:03:00.000Z', expectedVersion: 1 }),
+    ).rejects.toMatchObject({ name: 'VersionConflictError' });
+    expect(JSON.parse(bucket.store.get(versionKey('toyota_camry_2020', 2))!).winner).toBe(
+      true,
+    );
+  });
+
+  it('an unconditional write still probes forward and still never clobbers', async () => {
+    const e = env();
+    await writeTemplate(e, body(), { now: '2026-08-28T00:00:00.000Z' });
+    const bucket = e.DEFS_BUCKET as unknown as { store: Map<string, string> };
+    bucket.store.set(
+      versionKey('toyota_camry_2020', 2),
+      JSON.stringify({ version: 2, winner: true }),
+    );
+    const t = await writeTemplate(e, body(), { now: '2026-08-28T00:04:00.000Z' });
+    expect(t.version).toBe(3);
+    expect(JSON.parse(bucket.store.get(versionKey('toyota_camry_2020', 2))!).winner).toBe(
+      true,
+    );
+  });
+});
+```
+
+- [ ] **Step 2: Run and watch it fail**
+
+Run: `npx vitest run test/store.test.ts`
+Expected: FAIL — `VersionConflictError` is not exported, and `expectedVersion` is ignored.
+
+- [ ] **Step 3: Implement CAS in `src/store.ts`**
+
+Replace `WriteOptions` and `writeTemplate`:
+
+```ts
+export interface WriteOptions {
+  now: string;
+  author?: string;
+  // undefined: unconditional (import, backfill, dd-api -- unchanged behaviour).
+  // null:      the template must not exist yet.
+  // number:    the current head must be exactly this, and this write is head+1.
+  expectedVersion?: number | null;
+}
+
+export class VersionConflictError extends Error {
+  // Set explicitly, not inherited: src/index.ts tells expected states apart by
+  // `name` as well as `instanceof`, because a bundler or a future module
+  // boundary can break identity while the name survives.
+  name = 'VersionConflictError';
+  constructor(
+    public readonly expected: number | null,
+    public readonly actual: number,
+  ) {
+    super(
+      expected === null
+        ? `template already exists at version ${actual}`
+        : `expected version ${expected} but the current version is ${actual}`,
+    );
+  }
+}
+
+// An unconditional write probes forward past version objects the meta head has
+// not caught up with. Bounded, because an unbounded probe is a subrequest hole:
+// each step is one head() against a ~1,000-subrequest budget.
+const MAX_VERSION_PROBES = 32;
+
+export async function writeTemplate(
+  env: Env,
+  value: TemplateInput,
+  opts: WriteOptions,
+): Promise<Template> {
+  const meta = await readMeta(env, value.id);
+  const head = meta && !meta.deleted ? meta.head : 0;
+
+  if (opts.expectedVersion === null && head !== 0) {
+    throw new VersionConflictError(null, head);
+  }
+  if (typeof opts.expectedVersion === 'number' && opts.expectedVersion !== head) {
+    throw new VersionConflictError(opts.expectedVersion, head);
+  }
+
+  const action: VersionAction = meta && !meta.deleted ? 'update' : 'create';
+  // createdAt survives every later write, including a re-create after delete.
+  const createdAt = meta?.createdAt ?? opts.now;
+  const conditional = opts.expectedVersion !== undefined;
+
+  let version = head + 1;
+  let stored: Template | null = null;
+  let body = '';
+  for (let probe = 0; probe < (conditional ? 1 : MAX_VERSION_PROBES); probe++) {
+    const candidate: Template = {
+      ...value,
+      version,
+      ...(opts.author ? { author: opts.author } : {}),
+      createdAt,
+      updatedAt: opts.now,
+    };
+    body = JSON.stringify(candidate);
+    // Version first: if anything below fails, the immutable record still
+    // exists and the head simply lags, which is recoverable. The reverse is
+    // not. onlyIf is what makes the write a compare-and-swap rather than a
+    // read-then-hope: R2 returns null instead of overwriting.
+    const put = await env.DEFS_BUCKET.put(versionKey(value.id, version), body, {
+      onlyIf: { etagDoesNotMatch: '*' },
+    });
+    if (put !== null) {
+      stored = candidate;
+      break;
+    }
+    version++;
+  }
+
+  if (stored === null) {
+    if (conditional) {
+      // Somebody else took head+1 between our meta read and our put. Re-read
+      // the head so the caller is told the version it must rebase onto, not
+      // the stale one it sent.
+      const fresh = await readMeta(env, value.id);
+      throw new VersionConflictError(
+        opts.expectedVersion === undefined ? null : opts.expectedVersion,
+        fresh && !fresh.deleted ? fresh.head : head,
+      );
+    }
+    throw new Error(
+      `could not find a free version for ${value.id} within ${MAX_VERSION_PROBES} probes`,
+    );
+  }
+
+  await env.DEFS_BUCKET.put(templateKey(value.id), body);
+
+  const entry: VersionLogEntry = {
+    version: stored.version,
+    at: opts.now,
+    ...(opts.author ? { author: opts.author } : {}),
+    action,
+  };
+  const nextMeta: TemplateMeta = {
+    id: value.id,
+    head: stored.version,
+    createdAt,
+    versions: [...(meta?.versions ?? []), entry],
+  };
+  await env.DEFS_BUCKET.put(metaKey(value.id), JSON.stringify(nextMeta));
+  await env.DEFS_BUCKET.put(
+    historyKey(opts.now, value.id),
+    JSON.stringify({ id: value.id, ...entry }),
+  );
+
+  return stored;
+}
+```
+
+- [ ] **Step 4: Run the unit tests**
+
+Run: `npx vitest run test/store.test.ts test/write-path.test.ts && npm run typecheck`
+Expected: PASS.
+
+- [ ] **Step 5: Wire the preconditions onto `PUT /t/:id`**
+
+In `src/index.ts`, add the import:
+
+```ts
+import {
+  readTemplate,
+  writeTemplate,
+  deleteTemplate,
+  listHistoryPage,
+  VersionConflictError,
+} from './store';
+```
+
+and replace the `PUT` branch's write with:
+
+```ts
+const result = validateTemplate(body, vocab);
+if (!result.ok) return json({ errors: result.errors }, 422);
+
+// Preconditions. Absent means unconditional, which is what every existing
+// writer (import, backfill, dd-api) sends and what they keep getting.
+// Console always sends one, because two people editing one template is
+// exactly what the editor makes possible.
+let expectedVersion: number | null | undefined;
+const ifMatch = req.headers.get('if-match');
+const ifNoneMatch = req.headers.get('if-none-match');
+if (ifMatch !== null) {
+  const n = Number(ifMatch.replace(/^W\//, '').replace(/"/g, ''));
+  if (!Number.isInteger(n) || n < 1) {
+    return json(
+      { error: 'If-Match must be a quoted version integer, e.g. If-Match: "7"' },
+      400,
+    );
+  }
+  expectedVersion = n;
+} else if (ifNoneMatch !== null) {
+  if (ifNoneMatch.trim() !== '*') {
+    return json({ error: 'If-None-Match must be "*"' }, 400);
+  }
+  expectedVersion = null;
+}
+
+let stored;
+try {
+  stored = await writeTemplate(env, result.value, {
+    now,
+    author: result.value.author,
+    expectedVersion,
+  });
+} catch (err) {
+  const isConflict =
+    err instanceof VersionConflictError ||
+    (err instanceof Error && err.name === 'VersionConflictError');
+  if (!isConflict) throw err;
+  const c = err as VersionConflictError;
+  return json({ error: c.message, expected: c.expected, actual: c.actual }, 412);
+}
+await purgeUrls(env, id);
+return json(stored);
+```
+
+- [ ] **Step 6: Prove the _real_ R2 binding honours it**
+
+A `FakeBucket` that implements `onlyIf` proves only that the fake implements
+`onlyIf`. This project has already shipped a budget test that could not fail
+and a cached path that never ran the matcher. Create
+`test/integration/conditional-write.test.ts`:
+
+```ts
+import { SELF } from 'cloudflare:test';
+import { describe, expect, it } from 'vitest';
+
+const AUTH = {
+  'authorization': 'Bearer test-token-a',
+  'content-type': 'application/json',
+};
+const ID = 'toyota_cas_2020';
+const doc = {
+  id: ID,
+  deviceType: 'vehicle',
+  manufacturer: { slug: 'toyota', name: 'Toyota' },
+  model: 'CAS',
+  year: 2020,
+  attributes: { number_of_doors: 4 },
+  trims: [{ name: 'LE', attributes: { powertrain_type: 'ICE' } }],
+};
+
+const put = (headers: Record<string, string>) =>
+  SELF.fetch(`https://w/t/${ID}`, {
+    method: 'PUT',
+    headers: { ...AUTH, ...headers },
+    body: JSON.stringify(doc),
+  });
+
+describe('conditional writes against the real R2 binding', () => {
+  it('If-None-Match: * creates once and 412s the second time', async () => {
+    const created = await put({ 'if-none-match': '*' });
+    expect(created.status).toBe(200);
+    expect(((await created.json()) as { version: number }).version).toBe(1);
+
+    const again = await put({ 'if-none-match': '*' });
+    expect(again.status).toBe(412);
+    expect(await again.json()).toMatchObject({ expected: null, actual: 1 });
+  });
+
+  it('If-Match advances exactly once per version; the stale writer is refused', async () => {
+    const ok = await put({ 'if-match': '"1"' });
+    expect(ok.status).toBe(200);
+    expect(((await ok.json()) as { version: number }).version).toBe(2);
+
+    const stale = await put({ 'if-match': '"1"' });
+    expect(stale.status).toBe(412);
+    expect(await stale.json()).toMatchObject({ expected: 1, actual: 2 });
+
+    // The winner's immutable record is intact.
+    const v2 = await SELF.fetch(`https://w/t/${ID}`);
+    expect(((await v2.json()) as { version: number }).version).toBe(2);
+  });
+
+  it('a malformed If-Match is a 400, not a silent unconditional write', async () => {
+    const resp = await put({ 'if-match': 'W/"not-a-version"' });
+    expect(resp.status).toBe(400);
+  });
+
+  it('no precondition header still writes unconditionally, for import and dd-api', async () => {
+    const resp = await put({});
+    expect(resp.status).toBe(200);
+    expect(((await resp.json()) as { version: number }).version).toBe(3);
+  });
+});
+```
+
+- [ ] **Step 7: Run the integration suite**
+
+Run: `npm run test:integration`
+Expected: PASS — 41 integration tests.
+
+**If the `If-None-Match: *` case fails with a 200 instead of a 412,
+miniflare's R2 does not implement conditional puts. Do not delete the test.**
+Report it, and fall back to detection: after the version put, re-read
+`versionKey(id, version)` and compare a per-write nonce embedded in the body;
+a mismatch means another writer won, and the write reports a 412. That
+detects the clobber rather than preventing it — say so in the commit message
+and open a follow-up, because it leaves the loser's version object overwritten.
+
+- [ ] **Step 8: Full suite and commit**
+
+Run: `npm test && npm run test:integration && npm run typecheck`
+Expected: 199 unit + 41 integration, typecheck clean.
+
+```bash
+git add src/store.ts src/index.ts test/store.test.ts test/write-path.test.ts test/integration/conditional-write.test.ts
+git commit -m "feat(worker): compare-and-swap on template writes
+
+writeTemplate probed forward for a free version and wrote it unconditionally,
+so two concurrent saves could land on the same number and the second would
+overwrite the first's immutable version object. R2's onlyIf makes the version
+put a real CAS; If-Match/If-None-Match expose it, and absent preconditions
+keep the existing unconditional writers unchanged.
+
+The unit tests use a fake that implements onlyIf, which proves nothing about
+R2 -- test/integration/conditional-write.test.ts exercises the real binding."
+```
+
+---
+
+### Task 3: Generate the types from the schema — gate ③
+
+The spec calls for generating types from `schema/*.json`. Nothing does: the
+worker hand-wrote TS, dd-api hand-wrote the Go mirror, and Console would be the
+third copy of one contract. This task removes the worker's copy and gives
+Console (Task 4) a generator to run.
+
+**Files:**
+
+- Modify: `definitions-worker/schema/template.schema.json` (add `title` to `$defs` and `manufacturer`)
+- Create: `definitions-worker/scripts/gen-types.mjs`
+- Create: `definitions-worker/schema/generated/template.ts`
+- Modify: `definitions-worker/src/template.ts:1-60` (import the generated types)
+- Modify: `definitions-worker/package.json` (script + devDependency)
+- Create: `definitions-worker/test/generated-types.test.mjs`
+
+**Interfaces:**
+
+- Consumes: `schema/template.schema.json`.
+- Produces: `schema/generated/template.ts` exporting `Template`, `Trim`, `TrimSelectors`, `TemplateManufacturer`, `AttributeMap`; `npm run gen:types` and `npm run gen:types -- --check`.
+
+- [ ] **Step 1: Pin the generated names in the schema**
+
+`json-schema-to-typescript` names an interface from its `title`, falling back
+to the property or `$defs` key. Relying on the fallback means a schema edit can
+silently rename an exported type. Add these four `title` keys to
+`schema/template.schema.json` — annotations only, no validation change:
+
+- `properties.manufacturer` → `"title": "TemplateManufacturer"`
+- `$defs.trim` → `"title": "Trim"`
+- `$defs.selectors` → `"title": "TrimSelectors"`
+- `$defs.attributeMap` → `"title": "AttributeMap"`
+
+Each goes immediately after that object's `"type"` key, e.g.:
+
+```json
+    "trim": {
+      "type": "object",
+      "title": "Trim",
+      "required": ["name", "attributes"],
+```
+
+- [ ] **Step 2: Write the drift test first**
+
+Create `test/generated-types.test.mjs`:
+
+```js
+import { describe, expect, it } from 'vitest';
+import { readFile } from 'node:fs/promises';
+import { generate } from '../scripts/gen-types.mjs';
+
+describe('generated types', () => {
+  it('schema/generated/template.ts is what the schema produces right now', async () => {
+    const committed = await readFile(
+      new URL('../schema/generated/template.ts', import.meta.url),
+      'utf8',
+    );
+    expect(await generate()).toBe(committed);
+  });
+});
+```
+
+- [ ] **Step 3: Run it and watch it fail**
+
+Run: `npx vitest run test/generated-types.test.mjs`
+Expected: FAIL — `Cannot find module '../scripts/gen-types.mjs'`.
+
+- [ ] **Step 4: Add the generator**
+
+```bash
+npm install --save-dev json-schema-to-typescript@^15
+```
+
+Create `scripts/gen-types.mjs`:
+
+```js
+#!/usr/bin/env node
+// The contract lives in schema/*.json. Every hand-written mirror of it is a
+// copy that drifts -- there are already two (this worker's TS, dd-api's Go)
+// and Console would have been the third. `npm test` fails if the committed
+// output stops matching the schema.
+import { compile } from 'json-schema-to-typescript';
+import { readFile, writeFile, mkdir } from 'node:fs/promises';
+import { fileURLToPath } from 'node:url';
+
+const SCHEMA = new URL('../schema/template.schema.json', import.meta.url);
+const OUT = new URL('../schema/generated/template.ts', import.meta.url);
+
+const BANNER = `/* eslint-disable */
+// GENERATED by scripts/gen-types.mjs from schema/template.schema.json.
+// Do not edit. Run \`npm run gen:types\` after changing the schema.
+`;
+
+export async function generate() {
+  const schema = JSON.parse(await readFile(SCHEMA, 'utf8'));
+  const body = await compile(schema, 'Template', {
+    bannerComment: '',
+    additionalProperties: false,
+    style: { singleQuote: true, semi: true, printWidth: 100 },
+  });
+  return BANNER + body;
+}
+
+const isMain = process.argv[1] === fileURLToPath(import.meta.url);
+if (isMain) {
+  const generated = await generate();
+  if (process.argv.includes('--check')) {
+    const current = await readFile(OUT, 'utf8').catch(() => '');
+    if (current !== generated) {
+      console.error('schema/generated/template.ts is stale. Run: npm run gen:types');
+      process.exit(1);
+    }
+    console.log('generated types are up to date');
+  } else {
+    await mkdir(new URL('../schema/generated/', import.meta.url), { recursive: true });
+    await writeFile(OUT, generated);
+    console.log(`wrote ${fileURLToPath(OUT)}`);
+  }
+}
+```
+
+Add to `package.json` `scripts`:
+
+```json
+    "gen:types": "node scripts/gen-types.mjs",
+```
+
+and extend `test` so the drift check runs with everything else:
+
+```json
+    "test": "vitest run test/*.test.ts test/*.test.mjs test/extract/*.test.mjs",
+```
+
+(unchanged — `test/generated-types.test.mjs` already matches `test/*.test.mjs`).
+
+- [ ] **Step 5: Generate and inspect**
+
+Run: `npm run gen:types && cat schema/generated/template.ts`
+Expected: a file exporting `Template`, `TemplateManufacturer`, `Trim`, `TrimSelectors`, `AttributeMap`. Confirm those five names are present before continuing; if any differs, the `title` in Step 1 is missing or misplaced.
+
+- [ ] **Step 6: Make `src/template.ts` consume them**
+
+Delete the hand-written `TemplateManufacturer`, `TrimSelectors`, `Trim` and
+`Template` interfaces at `src/template.ts:24-58` and replace them with:
+
+```ts
+// The contract, generated from schema/template.schema.json. AttributeValue,
+// AttributeDef, DeviceType and TemplateValidation stay hand-written here: the
+// vocabulary is a separate document with no schema of its own, and
+// TemplateValidation is this module's own result type, not part of the wire
+// contract.
+export type {
+  Template,
+  TemplateManufacturer,
+  Trim,
+  TrimSelectors,
+  AttributeMap,
+} from '../schema/generated/template';
+import type { Template } from '../schema/generated/template';
+
+export type AttributeValue = string | number | boolean;
+export type TemplateInput = Omit<Template, 'version' | 'createdAt' | 'updatedAt'>;
+```
+
+Keep `AttributeDef`, `DeviceType` and `TemplateValidation` exactly as they are.
+
+- [ ] **Step 7: Typecheck and fix the fallout**
+
+Run: `npm run typecheck`
+Expected: PASS. The generated `AttributeMap` carries an index signature of
+`string | number | boolean`, which is what the hand-written one was; if
+`checkAttributes`' return type complains, annotate its local `out` as
+`Record<string, AttributeValue>` and return it — do not widen the generated type.
+
+- [ ] **Step 8: Full suite and commit**
+
+Run: `npm test && npm run test:integration && npm run typecheck`
+Expected: 200 unit (199 + the drift test) + 41 integration, typecheck clean.
+
+```bash
+git add schema/template.schema.json schema/generated/template.ts scripts/gen-types.mjs src/template.ts package.json package-lock.json test/generated-types.test.mjs
+git commit -m "feat(worker): generate template types from the schema
+
+The spec called for generating types rather than hand-writing them in four
+places. This removes the worker's copy and gives Console a generator to run
+against the same document. A test fails when the committed output stops
+matching the schema, so drift is a red build rather than a wrong type."
+```
+
+- [ ] **Step 9: Open the PR**
+
+```bash
+git push -u origin template-cas
+gh pr create --title "Worker gates for the Console editor: schema route, CAS, generated types" \
+  --body "$(cat <<'BODY'
+Three prerequisites the Console template editor cannot ship without.
+
+1. `GET /schema/<file>` — Console fetches the vehicle vocabulary at runtime so
+   the editor form cannot offer an option this worker rejects.
+2. Compare-and-swap on `writeTemplate`, exposed as `If-Match` / `If-None-Match`.
+   Two concurrent saves could previously probe to the same version number and
+   the second overwrote the first's immutable record. Absent preconditions stay
+   unconditional, so import, backfill and dd-api are unchanged.
+3. Types generated from `schema/template.schema.json`, replacing the worker's
+   hand-written copy. A drift test fails the build when they diverge.
+
+Stacked on `trim-extraction` (#1/#2/#3). 200 unit, 41 integration, typecheck clean.
+BODY
+)"
+```
+
+---
+
+# Phase 1 — the read path (repo: `dimo-developer-console`)
+
+```bash
+cd ~/workspace/dimo-developer-console
+git checkout master && git pull --ff-only
+git checkout -b template-editor
+npm test && npm run compile
+# baseline: suite green, typecheck clean
+```
+
+---
+
+### Task 4: Configuration, generated types, and the server-only worker client
+
+Everything Console knows about a template comes through here. It is
+server-only, by a runtime guard rather than by convention, because the whole
+point of gate ① is that `WRITE_TOKEN` never reaches a browser bundle.
+
+**Files:**
+
+- Modify: `src/config/index.ts`, `src/config/default.ts`, `src/config/production.ts`, `src/config/preview.ts`
+- Create: `scripts/gen-template-types.mjs`
+- Create: `src/types/generated/template.ts` (generated, committed)
+- Create: `src/types/template.ts`
+- Create: `src/services/definitions.ts`
+- Modify: `package.json`, `README.md`
+- Test: `__tests__/unit/services/definitions.test.ts`
+
+**Interfaces:**
+
+- Consumes: `GET /schema/template.schema.json`, `GET /schema/device-type-vehicle.json`, `GET /t/:id`, `PUT /t/:id` from Task 1 and Task 2.
+- Produces:
+  - `config.definitionsWorkerUrl: string`
+  - `src/types/template.ts` → `Template`, `Trim`, `TrimSelectors`, `TemplateManufacturer`, `AttributeMap`, `AttributeValue`, `AttributeDef`, `DeviceType`, `TemplatePayload`
+  - `fetchTemplate(id: string): Promise<Template | null>`
+  - `fetchVocabulary(): Promise<DeviceType>`
+  - `publishTemplate(id: string, payload: TemplatePayload, precondition: Precondition): Promise<PublishResult>`
+  - `type Precondition = { kind: 'create' } | { kind: 'update'; version: number }`
+  - `type PublishResult` — the discriminated union defined in Step 5.
+
+- [ ] **Step 1: Add the config**
+
+`src/config/index.ts` — add to the `Configuration` type, after `identityApiUrl`:
+
+```ts
+definitionsWorkerUrl: string;
+```
+
+`src/config/default.ts` and `src/config/preview.ts`:
+
+```ts
+export const definitionsWorkerUrl = 'https://definitions.dev.dimo.org';
+```
+
+`src/config/production.ts`:
+
+```ts
+export const definitionsWorkerUrl = 'https://definitions.dimo.org';
+```
+
+Document the two new **server-only** env vars in `README.md` beside the
+existing ones — no `NEXT_PUBLIC_` prefix on either, ever:
+
+```
+DEFINITIONS_WRITE_TOKEN=   # bearer token for PUT /t/:id on definitions-worker. Server-only.
+DIMO_CURATOR_ADDRESSES=    # comma-separated 0x addresses allowed to set hardwareTemplateId. Server-only.
+```
+
+- [ ] **Step 2: Generate the types from the live schema**
+
+Create `scripts/gen-template-types.mjs`:
+
+```js
+#!/usr/bin/env node
+// The template contract is definitions-worker/schema/template.schema.json,
+// served at <definitionsWorkerUrl>/schema/. Console generates from it rather
+// than hand-writing a third copy (the worker's TS and dd-api's Go are the
+// other two). Run after the contract changes; the output is committed.
+import { compile } from 'json-schema-to-typescript';
+import { writeFile, mkdir, readFile } from 'node:fs/promises';
+import { fileURLToPath } from 'node:url';
+
+const OUT = new URL('../src/types/generated/template.ts', import.meta.url);
+const BANNER = `/* eslint-disable */
+// GENERATED by scripts/gen-template-types.mjs from
+// definitions-worker/schema/template.schema.json. Do not edit.
+`;
+
+const fromFlag = process.argv.indexOf('--from');
+const source =
+  fromFlag !== -1
+    ? process.argv[fromFlag + 1]
+    : `${process.env.DEFINITIONS_WORKER_URL ?? 'https://definitions.dev.dimo.org'}/schema/template.schema.json`;
+
+const schema = source.startsWith('http')
+  ? await (await fetch(source)).json()
+  : JSON.parse(await readFile(source, 'utf8'));
+
+const body = await compile(schema, 'Template', {
+  bannerComment: '',
+  additionalProperties: false,
+  style: { singleQuote: true, semi: true, printWidth: 90 },
+});
+
+await mkdir(new URL('../src/types/generated/', import.meta.url), { recursive: true });
+await writeFile(OUT, BANNER + body);
+console.log(`wrote ${fileURLToPath(OUT)} from ${source}`);
+```
+
+```bash
+npm install --save-dev json-schema-to-typescript@^15
+npm run gen:template-types -- --from ../definitions-worker/schema/template.schema.json
+```
+
+after adding to `package.json` `scripts`:
+
+```json
+    "gen:template-types": "node scripts/gen-template-types.mjs",
+```
+
+Confirm `src/types/generated/template.ts` exports `Template`,
+`TemplateManufacturer`, `Trim`, `TrimSelectors` and `AttributeMap` before
+continuing.
+
+- [ ] **Step 3: Hand-write only what the schema does not carry**
+
+Create `src/types/template.ts`:
+
+```ts
+export type {
+  Template,
+  TemplateManufacturer,
+  Trim,
+  TrimSelectors,
+  AttributeMap,
+} from './generated/template';
+import type { Template } from './generated/template';
+
+export type AttributeValue = string | number | boolean;
+
+// The vehicle vocabulary (device-type-vehicle.json) has no schema of its own,
+// so these two are hand-written. They mirror definitions-worker/src/template.ts.
+export interface AttributeDef {
+  name: string;
+  label: string;
+  description?: string;
+  type: 'enum' | 'string' | 'number' | 'integer' | 'boolean';
+  unit?: string;
+  options?: string[];
+  minimum?: number;
+  maximum?: number;
+  variesByTrim?: boolean;
+}
+
+export interface DeviceType {
+  id: string;
+  name: string;
+  attributes: AttributeDef[];
+}
+
+// What Console is allowed to send. version, createdAt and updatedAt are
+// server-owned and the worker rejects them outright; author is stamped from
+// the session in src/app/api/templates/[id]/route.ts and is never client
+// input.
+export type TemplatePayload = Omit<
+  Template,
+  'version' | 'createdAt' | 'updatedAt' | 'author'
+>;
+```
+
+- [ ] **Step 4: Write the failing service test**
+
+Create `__tests__/unit/services/definitions.test.ts`:
+
+```ts
+import { fetchTemplate, fetchVocabulary, publishTemplate } from '@/services/definitions';
+import type { TemplatePayload } from '@/types/template';
+
+const payload = {
+  id: 'toyota_camry_2020',
+  deviceType: 'vehicle',
+  manufacturer: { slug: 'toyota', name: 'Toyota' },
+  model: 'Camry',
+  year: 2020,
+  attributes: {},
+  trims: [{ name: 'LE', attributes: {} }],
+} as unknown as TemplatePayload;
+
+const mockFetch = (impl: jest.Mock) => {
+  global.fetch = impl as unknown as typeof fetch;
+  return impl;
+};
+
+describe('definitions service', () => {
+  it('returns null for a template that does not exist yet', async () => {
+    mockFetch(
+      jest.fn().mockResolvedValue({ ok: false, status: 404, json: async () => ({}) }),
+    );
+    expect(await fetchTemplate('ineos_grenadier_2024')).toBeNull();
+  });
+
+  it('sends If-None-Match on create and If-Match on update, and never the token to the body', async () => {
+    process.env.DEFINITIONS_WRITE_TOKEN = 'secret-token';
+    const f = mockFetch(
+      jest
+        .fn()
+        .mockResolvedValue({
+          ok: true,
+          status: 200,
+          json: async () => ({ ...payload, version: 1 }),
+        }),
+    );
+
+    await publishTemplate('toyota_camry_2020', payload, { kind: 'create' });
+    expect(f.mock.calls[0][1].headers['If-None-Match']).toBe('*');
+    expect(f.mock.calls[0][1].headers.Authorization).toBe('Bearer secret-token');
+    expect(f.mock.calls[0][1].body).not.toContain('secret-token');
+
+    await publishTemplate('toyota_camry_2020', payload, { kind: 'update', version: 7 });
+    expect(f.mock.calls[1][1].headers['If-Match']).toBe('"7"');
+  });
+
+  it('maps 422 to validation errors and 412 to a conflict', async () => {
+    mockFetch(
+      jest.fn().mockResolvedValue({
+        ok: false,
+        status: 422,
+        json: async () => ({ errors: ['template: unknown attribute "nope"'] }),
+      }),
+    );
+    expect(
+      await publishTemplate('toyota_camry_2020', payload, { kind: 'create' }),
+    ).toEqual({
+      ok: false,
+      kind: 'validation',
+      errors: ['template: unknown attribute "nope"'],
+    });
+
+    mockFetch(
+      jest.fn().mockResolvedValue({
+        ok: false,
+        status: 412,
+        json: async () => ({
+          error: 'expected version 6 but the current version is 7',
+          expected: 6,
+          actual: 7,
+        }),
+      }),
+    );
+    expect(
+      await publishTemplate('toyota_camry_2020', payload, { kind: 'update', version: 6 }),
+    ).toEqual({
+      ok: false,
+      kind: 'conflict',
+      expected: 6,
+      actual: 7,
+    });
+  });
+
+  it('refuses a payload over the worker 64KB cap before spending a request', async () => {
+    const f = mockFetch(jest.fn());
+    const fat = {
+      ...payload,
+      trims: Array.from({ length: 4000 }, (_, i) => ({ name: `T${i}`, attributes: {} })),
+    };
+    const result = await publishTemplate(
+      'toyota_camry_2020',
+      fat as unknown as TemplatePayload,
+      { kind: 'create' },
+    );
+    expect(result).toMatchObject({ ok: false, kind: 'too-large' });
+    expect(f).not.toHaveBeenCalled();
+  });
+
+  it('fetches the vocabulary from the worker, not from a vendored copy', async () => {
+    const f = mockFetch(
+      jest
+        .fn()
+        .mockResolvedValue({
+          ok: true,
+          status: 200,
+          json: async () => ({ id: 'vehicle', name: 'Vehicle', attributes: [] }),
+        }),
+    );
+    await fetchVocabulary();
+    expect(f.mock.calls[0][0]).toContain('/schema/device-type-vehicle.json');
+  });
+});
+```
+
+- [ ] **Step 5: Run it and watch it fail**
+
+Run: `npx jest __tests__/unit/services/definitions.test.ts`
+Expected: FAIL — `Cannot find module '@/services/definitions'`.
+
+- [ ] **Step 6: Implement the client**
+
+Create `src/services/definitions.ts`:
+
+```ts
+import config from '@/config';
+import type { DeviceType, Template, TemplatePayload } from '@/types/template';
+
+// definitions-worker/src/index.ts MAX_DOC_BYTES. Checked here so an oversized
+// draft is reported in the editor rather than as an opaque 413 after a
+// round trip.
+const MAX_DOC_BYTES = 64 * 1024;
+
+// Gate ①: WRITE_TOKEN must never reach a browser bundle. A convention is not
+// a guarantee; this is. Any client component that imports this module fails
+// loudly in development instead of shipping the token.
+function assertServer(): void {
+  if (typeof window !== 'undefined') {
+    throw new Error(
+      'services/definitions is server-only — it holds DEFINITIONS_WRITE_TOKEN',
+    );
+  }
+}
+
+export type Precondition = { kind: 'create' } | { kind: 'update'; version: number };
+
+export type PublishResult =
+  | { ok: true; template: Template }
+  | { ok: false; kind: 'validation'; errors: string[] }
+  | { ok: false; kind: 'conflict'; expected: number | null; actual: number }
+  | { ok: false; kind: 'too-large'; bytes: number; limit: number }
+  | { ok: false; kind: 'upstream'; status: number; message: string };
+
+export async function fetchTemplate(id: string): Promise<Template | null> {
+  assertServer();
+  const resp = await fetch(`${config.definitionsWorkerUrl}/t/${encodeURIComponent(id)}`, {
+    // A template's ETag is its version, and the editor's whole conflict story
+    // depends on holding the current one. Never serve this from a cache.
+    cache: 'no-store',
+  });
+  if (resp.status === 404) return null;
+  if (!resp.ok)
+    throw new Error(`definitions-worker GET /t/${id} returned ${resp.status}`);
+  return (await resp.json()) as Template;
+}
+
+export async function fetchVocabulary(): Promise<DeviceType> {
+  assertServer();
+  const resp = await fetch(
+    `${config.definitionsWorkerUrl}/schema/device-type-vehicle.json`,
+    {
+      // Matches the worker's own max-age. The vocabulary decides which options
+      // the form offers, so it is the one document that must not go stale for
+      // longer than the validator that enforces it.
+      next: { revalidate: 300 },
+    },
+  );
+  if (!resp.ok)
+    throw new Error(
+      `definitions-worker GET /schema/device-type-vehicle.json returned ${resp.status}`,
+    );
+  return (await resp.json()) as DeviceType;
+}
+
+export async function publishTemplate(
+  id: string,
+  payload: TemplatePayload,
+  precondition: Precondition,
+): Promise<PublishResult> {
+  assertServer();
+  const body = JSON.stringify(payload);
+  const bytes = new TextEncoder().encode(body).byteLength;
+  if (bytes > MAX_DOC_BYTES) {
+    return { ok: false, kind: 'too-large', bytes, limit: MAX_DOC_BYTES };
+  }
+
+  const headers: Record<string, string> = {
+    'Content-Type': 'application/json',
+    'Authorization': `Bearer ${process.env.DEFINITIONS_WRITE_TOKEN ?? ''}`,
+  };
+  if (precondition.kind === 'create') headers['If-None-Match'] = '*';
+  else headers['If-Match'] = `"${precondition.version}"`;
+
+  const resp = await fetch(`${config.definitionsWorkerUrl}/t/${encodeURIComponent(id)}`, {
+    method: 'PUT',
+    headers,
+    body,
+    cache: 'no-store',
+  });
+
+  if (resp.ok) return { ok: true, template: (await resp.json()) as Template };
+
+  const data = (await resp.json().catch(() => ({}))) as {
+    error?: string;
+    errors?: string[];
+    expected?: number | null;
+    actual?: number;
+  };
+
+  if (resp.status === 422)
+    return { ok: false, kind: 'validation', errors: data.errors ?? [] };
+  if (resp.status === 412) {
+    return {
+      ok: false,
+      kind: 'conflict',
+      expected: data.expected ?? null,
+      actual: data.actual ?? 0,
+    };
+  }
+  if (resp.status === 413)
+    return { ok: false, kind: 'too-large', bytes, limit: MAX_DOC_BYTES };
+  return {
+    ok: false,
+    kind: 'upstream',
+    status: resp.status,
+    message: data.error ?? `HTTP ${resp.status}`,
+  };
+}
+```
+
+- [ ] **Step 7: Run the tests**
+
+Run: `npx jest __tests__/unit/services/definitions.test.ts && npm run compile`
+Expected: PASS, 6 tests; typecheck clean.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add src/config src/types scripts/gen-template-types.mjs src/services/definitions.ts \
+  __tests__/unit/services/definitions.test.ts package.json package-lock.json README.md
+git commit -m "feat(templates): typed, server-only client for definitions-worker
+
+Types are generated from the worker's schema rather than hand-written a third
+time, and the vocabulary is fetched at runtime so the editor form cannot offer
+an option the validator rejects. A runtime guard makes the server-only rule a
+guarantee instead of a convention: DEFINITIONS_WRITE_TOKEN cannot reach a
+browser bundle without throwing."
+```
+
+---
+
+### Task 5: The divergence model
+
+The heart of the feature, and pure — no React, no fetch, no dates. Every edit
+returns a new template. If this module is right, the UI is a rendering of it;
+if it is wrong, no amount of UI hides it.
+
+Two invariants it enforces so the UI cannot violate them:
+
+1. **An attribute is on the template or on the trims, never both.** Editing one
+   trim's value for a currently-shared attribute pushes that value down to
+   every trim first. Setting a shared value clears it from every trim.
+2. **Absent is not empty.** Clearing removes the key. `undefined` is the only
+   representation of "not set"; `''` never enters a template.
+
+**Files:**
+
+- Create: `src/utils/templateGrid.ts`
+- Create: `src/utils/__tests__/fixtures/toyota_camry_2020.json` (copy of `definitions-worker/schema/examples/toyota_camry_2020.json`)
+- Create: `src/utils/__tests__/fixtures/vehicleVocab.ts`
+- Test: `src/utils/__tests__/templateGrid.test.ts`
+
+**Interfaces:**
+
+- Consumes: `Template`, `Trim`, `TrimSelectors`, `AttributeValue`, `AttributeDef`, `DeviceType`, `TemplatePayload` from `@/types/template`.
+- Produces:
+  - `buildGrid(template: Template, vocab: DeviceType): Grid`
+  - `Grid { trims: Trim[]; rows: GridRow[] }`
+  - `GridRow { def: AttributeDef; scope: 'shared' | 'trim' | 'absent'; shared?: AttributeValue; cells: (AttributeValue | undefined)[]; distinct: number; absentCount: number; canLift: boolean }`
+  - `setShared`, `clearShared`, `setTrimValue`, `clearTrimValue`, `liftToShared`, `pushDownToTrims`, `addTrim`, `removeTrim`, `renameTrim`, `setSelectors`, `setHardwareTemplateId` — all `(template, ...args) => Template`
+  - `hasEffectiveSelector(selectors?: TrimSelectors): boolean`
+  - `toPayload(template: Template): TemplatePayload`
+
+- [ ] **Step 1: Copy the fixtures**
+
+```bash
+mkdir -p src/utils/__tests__/fixtures
+cp ../definitions-worker/schema/examples/toyota_camry_2020.json src/utils/__tests__/fixtures/
+```
+
+Create `src/utils/__tests__/fixtures/vehicleVocab.ts` holding the 14 attribute
+definitions from `definitions-worker/schema/device-type-vehicle.json`, typed as
+`DeviceType`. Copy them verbatim — `powertrain_type`, `fuel_type`,
+`driven_wheels`, `vehicle_type`, `number_of_doors`, `base_msrp`,
+`fuel_tank_capacity_gal`, `battery_capacity_kwh`, `mpg_city`, `mpg_highway`,
+`mpg_combined`, `wheelbase_in`, `manufacturer_code`, `emissions_standard` —
+with their `label`, `type`, `unit`, `options`, `minimum`, `maximum` and
+`variesByTrim` exactly as the JSON has them. This is a test fixture; the
+running app always fetches the live vocabulary.
+
+- [ ] **Step 2: Write the failing tests**
+
+Create `src/utils/__tests__/templateGrid.test.ts`:
+
+```ts
+import camry from './fixtures/toyota_camry_2020.json';
+import { vehicleVocab } from './fixtures/vehicleVocab';
+import {
+  buildGrid,
+  setShared,
+  clearShared,
+  setTrimValue,
+  clearTrimValue,
+  liftToShared,
+  pushDownToTrims,
+  addTrim,
+  removeTrim,
+  hasEffectiveSelector,
+  toPayload,
+} from '../templateGrid';
+import type { Template } from '@/types/template';
+
+const t = camry as unknown as Template;
+const row = (tpl: Template, name: string) =>
+  buildGrid(tpl, vehicleVocab).rows.find((r) => r.def.name === name)!;
+
+describe('buildGrid', () => {
+  it('renders every vocabulary attribute, including ones the template does not set', () => {
+    const grid = buildGrid(t, vehicleVocab);
+    expect(grid.rows).toHaveLength(vehicleVocab.attributes.length);
+    expect(grid.rows.map((r) => r.def.name)).toEqual(
+      vehicleVocab.attributes.map((a) => a.name),
+    );
+    expect(row(t, 'emissions_standard').scope).toBe('absent');
+  });
+
+  it('names the two attributes the production record blended', () => {
+    // toyota_camry_2020 in production says powertrain_type ICE with hybrid
+    // tank and mpg figures. In the template those are the divergent rows, and
+    // this test is the regression that says so.
+    expect(row(t, 'powertrain_type').distinct).toBeGreaterThan(1);
+    expect(row(t, 'fuel_tank_capacity_gal').distinct).toBeGreaterThan(1);
+  });
+
+  it('counts shared attributes as one value and offers no lift', () => {
+    const doors = row(t, 'number_of_doors');
+    expect(doors.scope).toBe('shared');
+    expect(doors.shared).toBe(4);
+    expect(doors.distinct).toBe(1);
+    expect(doors.canLift).toBe(false);
+  });
+
+  it('offers a lift only when every trim agrees and none is absent', () => {
+    const agreed = setTrimValue(t, 0, 'mpg_highway', 39);
+    let all = agreed;
+    all.trims.forEach((_, i) => {
+      all = setTrimValue(all, i, 'mpg_highway', 39);
+    });
+    expect(row(all, 'mpg_highway').canLift).toBe(true);
+
+    const oneMissing = clearTrimValue(all, 3, 'mpg_highway');
+    expect(row(oneMissing, 'mpg_highway').canLift).toBe(false);
+    expect(row(oneMissing, 'mpg_highway').absentCount).toBe(1);
+  });
+});
+
+describe('the template-or-trim invariant', () => {
+  it('setting one trim value pushes a shared attribute down to every trim first', () => {
+    const next = setTrimValue(t, 0, 'number_of_doors', 2);
+    expect(next.attributes.number_of_doors).toBeUndefined();
+    expect(next.trims[0].attributes.number_of_doors).toBe(2);
+    next.trims
+      .slice(1)
+      .forEach((trim) => expect(trim.attributes.number_of_doors).toBe(4));
+  });
+
+  it('setting a shared value clears the attribute from every trim', () => {
+    const next = setShared(t, 'powertrain_type', 'ICE');
+    expect(next.attributes.powertrain_type).toBe('ICE');
+    next.trims.forEach((trim) => expect(trim.attributes.powertrain_type).toBeUndefined());
+  });
+
+  it('lift and push down are inverses', () => {
+    const pushed = pushDownToTrims(t, 'number_of_doors');
+    expect(pushed.attributes.number_of_doors).toBeUndefined();
+    const lifted = liftToShared(pushed, 'number_of_doors');
+    expect(lifted.attributes.number_of_doors).toBe(4);
+    lifted.trims.forEach((trim) =>
+      expect(trim.attributes.number_of_doors).toBeUndefined(),
+    );
+  });
+
+  it('never mutates the template it was given', () => {
+    const before = JSON.stringify(t);
+    setTrimValue(t, 0, 'mpg_city', 99);
+    setShared(t, 'mpg_city', 99);
+    clearShared(t, 'number_of_doors');
+    removeTrim(t, 0);
+    expect(JSON.stringify(t)).toBe(before);
+  });
+});
+
+describe('absent is not empty', () => {
+  it('clearing removes the key rather than storing an empty value', () => {
+    const cleared = clearTrimValue(t, 0, 'mpg_city');
+    expect('mpg_city' in cleared.trims[0].attributes).toBe(false);
+    expect(JSON.stringify(cleared)).not.toContain('""');
+  });
+
+  it('toPayload drops server-owned fields and empty selector containers', () => {
+    const withEmpties = setSelectorsForTest(t);
+    const payload = toPayload(withEmpties) as Record<string, unknown>;
+    expect(payload.version).toBeUndefined();
+    expect(payload.createdAt).toBeUndefined();
+    expect(payload.updatedAt).toBeUndefined();
+    expect(payload.author).toBeUndefined();
+    const trims = payload.trims as { selectors?: unknown }[];
+    expect(trims[0].selectors).toBeUndefined();
+  });
+});
+
+describe('hasEffectiveSelector — gate 4', () => {
+  it.each([
+    [undefined, false],
+    [{}, false],
+    [{ manufacturerCode: [] }, false],
+    [{ manufacturerCode: [''] }, false],
+    [{ manufacturerCode: ['   '] }, false],
+    [{ styleName: [''] }, false],
+    [{ vinPattern: '' }, false],
+    [{ vinPattern: '   ' }, false],
+    [{ manufacturerCode: ['2532'] }, true],
+    [{ styleName: ['Hybrid LE'] }, true],
+    [{ vinPattern: '^4T1B11HK.*$' }, true],
+  ])('%p -> %p', (selectors, expected) => {
+    expect(hasEffectiveSelector(selectors as never)).toBe(expected);
+  });
+});
+
+describe('trims', () => {
+  it('addTrim appends an empty, selector-less, uniquely named trim', () => {
+    const next = addTrim(t, 'XLE V6');
+    expect(next.trims).toHaveLength(t.trims.length + 1);
+    expect(next.trims.at(-1)).toEqual({ name: 'XLE V6', attributes: {} });
+  });
+
+  it('removeTrim keeps at least one trim', () => {
+    const single = { ...t, trims: [t.trims[0]] };
+    expect(removeTrim(single, 0).trims).toHaveLength(1);
+  });
+});
+
+// Helper: puts a degenerate selector on trim 0 so toPayload has something to drop.
+function setSelectorsForTest(template: Template): Template {
+  const trims = template.trims.map((trim, i) =>
+    i === 0 ? { ...trim, selectors: { manufacturerCode: [''] } } : trim,
+  );
+  return { ...template, trims };
+}
+```
+
+- [ ] **Step 3: Run and watch it fail**
+
+Run: `npx jest src/utils/__tests__/templateGrid.test.ts`
+Expected: FAIL — `Cannot find module '../templateGrid'`.
+
+- [ ] **Step 4: Implement the model**
+
+Create `src/utils/templateGrid.ts`:
+
+```ts
+import type {
+  AttributeDef,
+  AttributeValue,
+  DeviceType,
+  Template,
+  TemplatePayload,
+  Trim,
+  TrimSelectors,
+} from '@/types/template';
+
+export type Scope = 'shared' | 'trim' | 'absent';
+
+export interface GridRow {
+  def: AttributeDef;
+  scope: Scope;
+  shared?: AttributeValue;
+  /** One entry per trim, in trim order. `undefined` means not set — never ''. */
+  cells: (AttributeValue | undefined)[];
+  /** Distinct values across trims. 1 on a shared row: that is the point of shared. */
+  distinct: number;
+  absentCount: number;
+  canLift: boolean;
+}
+
+export interface Grid {
+  trims: Trim[];
+  rows: GridRow[];
+}
+
+const attrs = (map: Record<string, AttributeValue> | undefined) => map ?? {};
+
+/**
+ * Rows follow vocabulary order, always. Sorting divergent rows to the top would
+ * move an attribute every time someone edited it; the design puts the emphasis
+ * on contrast instead, so positions stay learnable. Every vocabulary attribute
+ * gets a row even when nothing sets it — 5,152 templates in the current emitted
+ * set carry no attributes at all, so "empty" is the common case and an empty
+ * row is the affordance for filling it in.
+ */
+export function buildGrid(template: Template, vocab: DeviceType): Grid {
+  const rows = vocab.attributes.map<GridRow>((def) => {
+    const shared = attrs(template.attributes)[def.name];
+    const cells = template.trims.map((t) => attrs(t.attributes)[def.name]);
+    const present = cells.filter((v): v is AttributeValue => v !== undefined);
+    const distinct = new Set(present.map((v) => JSON.stringify(v))).size;
+    const scope: Scope =
+      shared !== undefined ? 'shared' : present.length > 0 ? 'trim' : 'absent';
+    return {
+      def,
+      scope,
+      ...(shared !== undefined ? { shared } : {}),
+      cells,
+      distinct: scope === 'shared' ? 1 : distinct,
+      absentCount: scope === 'shared' ? 0 : cells.length - present.length,
+      // Lifting a single-trim template's attribute changes nothing, so the
+      // offer would be pure noise. Only worth surfacing where agreement is a
+      // fact about several trims.
+      canLift:
+        scope === 'trim' &&
+        distinct === 1 &&
+        present.length === cells.length &&
+        cells.length > 1,
+    };
+  });
+  return { trims: template.trims, rows };
+}
+
+const withoutKey = (map: Record<string, AttributeValue>, key: string) => {
+  const { [key]: _dropped, ...rest } = map;
+  return rest;
+};
+
+const mapTrims = (t: Template, fn: (trim: Trim, index: number) => Trim): Template => ({
+  ...t,
+  trims: t.trims.map(fn),
+});
+
+/** Shared value wins outright: the attribute cannot also live on a trim. */
+export function setShared(t: Template, name: string, value: AttributeValue): Template {
+  const next = mapTrims(t, (trim) => ({
+    ...trim,
+    attributes: withoutKey(attrs(trim.attributes), name),
+  }));
+  return { ...next, attributes: { ...attrs(t.attributes), [name]: value } };
+}
+
+export function clearShared(t: Template, name: string): Template {
+  return { ...t, attributes: withoutKey(attrs(t.attributes), name) };
+}
+
+/**
+ * The move that makes divergence expressible. If the attribute is currently
+ * shared, it is pushed down onto every trim first — otherwise the result would
+ * carry the attribute in both places, which the worker rejects with
+ * `"<k>" is on both the template and trim <name> — pick one`.
+ */
+export function setTrimValue(
+  t: Template,
+  index: number,
+  name: string,
+  value: AttributeValue,
+): Template {
+  const base = attrs(t.attributes)[name] !== undefined ? pushDownToTrims(t, name) : t;
+  return mapTrims(base, (trim, i) =>
+    i === index
+      ? { ...trim, attributes: { ...attrs(trim.attributes), [name]: value } }
+      : trim,
+  );
+}
+
+/** Removes the key. There is no empty value to store. */
+export function clearTrimValue(t: Template, index: number, name: string): Template {
+  return mapTrims(t, (trim, i) =>
+    i === index
+      ? { ...trim, attributes: withoutKey(attrs(trim.attributes), name) }
+      : trim,
+  );
+}
+
+export function pushDownToTrims(t: Template, name: string): Template {
+  const value = attrs(t.attributes)[name];
+  if (value === undefined) return t;
+  const next = mapTrims(t, (trim) => ({
+    ...trim,
+    attributes: { ...attrs(trim.attributes), [name]: value },
+  }));
+  return { ...next, attributes: withoutKey(attrs(t.attributes), name) };
+}
+
+/** The correct modelling action when the divergence rail reads 1. */
+export function liftToShared(t: Template, name: string): Template {
+  const values = t.trims.map((trim) => attrs(trim.attributes)[name]);
+  if (values.some((v) => v === undefined)) return t;
+  if (new Set(values.map((v) => JSON.stringify(v))).size !== 1) return t;
+  const next = mapTrims(t, (trim) => ({
+    ...trim,
+    attributes: withoutKey(attrs(trim.attributes), name),
+  }));
+  return {
+    ...next,
+    attributes: { ...attrs(t.attributes), [name]: values[0] as AttributeValue },
+  };
+}
+
+export function addTrim(t: Template, name: string): Template {
+  return { ...t, trims: [...t.trims, { name, attributes: {} }] };
+}
+
+/** The schema requires minItems 1: a model-year sold one way still has a trim. */
+export function removeTrim(t: Template, index: number): Template {
+  if (t.trims.length <= 1) return t;
+  return { ...t, trims: t.trims.filter((_, i) => i !== index) };
+}
+
+export function renameTrim(t: Template, index: number, name: string): Template {
+  return mapTrims(t, (trim, i) => (i === index ? { ...trim, name } : trim));
+}
+
+export function setSelectors(
+  t: Template,
+  index: number,
+  selectors: TrimSelectors,
+): Template {
+  return mapTrims(t, (trim, i) => (i === index ? { ...trim, selectors } : trim));
+}
+
+export function setHardwareTemplateId(t: Template, value: string | undefined): Template {
+  if (value === undefined || value === '') {
+    const { hardwareTemplateId: _dropped, ...rest } = t;
+    return rest as Template;
+  }
+  return { ...t, hardwareTemplateId: value };
+}
+
+/**
+ * Mirrors definitions-worker/src/template.ts hasSelector, degenerate cases
+ * included. A trim that fails this on a multi-trim template matches every
+ * signal and makes every decode for the model-year ambiguous.
+ */
+export function hasEffectiveSelector(selectors?: TrimSelectors): boolean {
+  if (!selectors) return false;
+  if (selectors.manufacturerCode?.some((c) => c.trim().length > 0)) return true;
+  if (selectors.styleName?.some((n) => n.trim().length > 0)) return true;
+  return (
+    typeof selectors.vinPattern === 'string' && selectors.vinPattern.trim().length > 0
+  );
+}
+
+const pruneSelectors = (selectors?: TrimSelectors): TrimSelectors | undefined => {
+  if (!selectors) return undefined;
+  const out: TrimSelectors = {};
+  const codes =
+    selectors.manufacturerCode?.map((c) => c.trim()).filter((c) => c.length > 0) ?? [];
+  const names =
+    selectors.styleName?.map((n) => n.trim()).filter((n) => n.length > 0) ?? [];
+  if (codes.length > 0) out.manufacturerCode = codes;
+  if (names.length > 0) out.styleName = names;
+  if (selectors.vinPattern && selectors.vinPattern.trim().length > 0)
+    out.vinPattern = selectors.vinPattern.trim();
+  return Object.keys(out).length > 0 ? out : undefined;
+};
+
+/**
+ * What goes on the wire. version, createdAt and updatedAt are server-owned and
+ * the worker rejects them as unexpected top-level keys; author is stamped from
+ * the session server-side. Empty selector containers are dropped rather than
+ * sent — but dropping them does not make a selector-less trim legal, and
+ * templateValidate.ts is what says so before save.
+ */
+export function toPayload(t: Template): TemplatePayload {
+  const { version: _v, createdAt: _c, updatedAt: _u, author: _a, ...rest } = t;
+  return {
+    ...rest,
+    attributes: attrs(t.attributes),
+    trims: t.trims.map((trim) => {
+      const selectors = pruneSelectors(trim.selectors);
+      return {
+        name: trim.name,
+        ...(selectors ? { selectors } : {}),
+        ...(trim.hardwareTemplateId
+          ? { hardwareTemplateId: trim.hardwareTemplateId }
+          : {}),
+        attributes: attrs(trim.attributes),
+      };
+    }),
+  } as TemplatePayload;
+}
+```
+
+- [ ] **Step 5: Run the tests**
+
+Run: `npx jest src/utils/__tests__/templateGrid.test.ts && npm run compile`
+Expected: PASS, all cases; typecheck clean.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add src/utils/templateGrid.ts src/utils/__tests__/
+git commit -m "feat(templates): the divergence model
+
+Trims as columns, attributes as rows, and the two contract invariants enforced
+in the model rather than left to the UI: an attribute lives on the template or
+on the trims and never both, and clearing removes the key rather than storing
+an empty value. Editing one trim's value for a shared attribute pushes it down
+first, which is what makes divergence expressible at all.
+
+Tested against the real ten-trim Camry, including the regression that
+powertrain_type and fuel_tank_capacity_gal are the divergent rows -- the pair
+the production record blended."
+```
+
+---
+
+### Task 6: Typed coercion, the normalisation report, and the validation mirror
+
+Section 8 of the handoff asks the question this task answers: _when the editor
+declines to save something, or quietly normalises it, does the person see that
+happen?_ Two modules, one task, because the report is worthless without the
+coercion that produces it.
+
+**Files:**
+
+- Create: `src/utils/templateCoerce.ts`
+- Create: `src/utils/templateValidate.ts`
+- Test: `src/utils/__tests__/templateCoerce.test.ts`
+- Test: `src/utils/__tests__/templateValidate.test.ts`
+
+**Interfaces:**
+
+- Consumes: `AttributeDef`, `AttributeValue`, `DeviceType`, `Template` from `@/types/template`; `hasEffectiveSelector` from `@/utils/templateGrid`.
+- Produces:
+  - `coerce(def: AttributeDef, raw: string): CoerceResult`
+  - `CoerceResult = { kind: 'value'; value: AttributeValue; note?: Normalisation } | { kind: 'clear'; note: Normalisation } | { kind: 'error'; message: string }`
+  - `Normalisation { attribute: string; from: string; to: AttributeValue | null; reason: string }`
+  - `validateDraft(template: Template, vocab: DeviceType): string[]` — the worker's error strings, verbatim, in the worker's order.
+
+- [ ] **Step 1: Write the failing coercion tests**
+
+Create `src/utils/__tests__/templateCoerce.test.ts`:
+
+```ts
+import { coerce } from '../templateCoerce';
+import { vehicleVocab } from './fixtures/vehicleVocab';
+
+const def = (name: string) => vehicleVocab.attributes.find((a) => a.name === name)!;
+
+describe('coerce', () => {
+  it('parses a stringified number into a number and says it did', () => {
+    expect(coerce(def('fuel_tank_capacity_gal'), '15.800000')).toEqual({
+      kind: 'value',
+      value: 15.8,
+      note: {
+        attribute: 'fuel_tank_capacity_gal',
+        from: '15.800000',
+        to: 15.8,
+        reason: 'stored as the number 15.8, not the text "15.800000"',
+      },
+    });
+  });
+
+  it('does not report a note when nothing was changed', () => {
+    expect(coerce(def('mpg_city'), '28')).toEqual({ kind: 'value', value: 28 });
+  });
+
+  it('treats an empty or whitespace input as a removal, never as an empty value', () => {
+    for (const raw of ['', '   ']) {
+      expect(coerce(def('mpg_city'), raw)).toEqual({
+        kind: 'clear',
+        note: {
+          attribute: 'mpg_city',
+          from: raw,
+          to: null,
+          reason: 'cleared — the attribute is removed, not stored empty',
+        },
+      });
+    }
+  });
+
+  it('refuses a value outside the vocabulary bounds with the reason', () => {
+    expect(coerce(def('mpg_city'), '400')).toEqual({
+      kind: 'error',
+      message: 'template: "mpg_city" above maximum 200',
+    });
+  });
+
+  it('refuses a non-integer for an integer attribute', () => {
+    expect(coerce(def('number_of_doors'), '4.5')).toEqual({
+      kind: 'error',
+      message: 'template: "number_of_doors" must be an integer',
+    });
+  });
+
+  it('refuses a value outside an enum options list', () => {
+    expect(coerce(def('powertrain_type'), 'Hybrid')).toEqual({
+      kind: 'error',
+      message:
+        'template: "powertrain_type"="Hybrid" is not one of ["ICE","HEV","PHEV","BEV","FCEV"]',
+    });
+  });
+
+  it('names the trim when one is given', () => {
+    expect(coerce(def('mpg_city'), '400', 'trim LE')).toEqual({
+      kind: 'error',
+      message: 'trim LE: "mpg_city" above maximum 200',
+    });
+  });
+
+  it('trims surrounding whitespace on a string attribute and says it did', () => {
+    expect(coerce(def('manufacturer_code'), '  2532 ')).toEqual({
+      kind: 'value',
+      value: '2532',
+      note: {
+        attribute: 'manufacturer_code',
+        from: '  2532 ',
+        to: '2532',
+        reason: 'surrounding whitespace removed',
+      },
+    });
+  });
+});
+```
+
+- [ ] **Step 2: Run and watch it fail**
+
+Run: `npx jest src/utils/__tests__/templateCoerce.test.ts`
+Expected: FAIL — module not found. (8 cases once implemented.)
+
+- [ ] **Step 3: Implement coercion**
+
+Create `src/utils/templateCoerce.ts`:
+
+```ts
+import type { AttributeDef, AttributeValue } from '@/types/template';
+
+export interface Normalisation {
+  attribute: string;
+  from: string;
+  /** null means the attribute was removed. */
+  to: AttributeValue | null;
+  reason: string;
+}
+
+export type CoerceResult =
+  | { kind: 'value'; value: AttributeValue; note?: Normalisation }
+  | { kind: 'clear'; note: Normalisation }
+  | { kind: 'error'; message: string };
+
+/**
+ * One text input becomes one typed attribute value, or a removal, or a named
+ * refusal. Never silently: every difference between what was typed and what
+ * gets stored produces a Normalisation, which NormalisationPanel shows before
+ * save. Error messages are the worker's own strings (see
+ * definitions-worker/src/template.ts checkAttributes) so the editor and the
+ * validator never describe the same fault two different ways. `where` names the
+ * place the way the worker does -- 'template' or 'trim LE'.
+ */
+export function coerce(def: AttributeDef, raw: string, where = 'template'): CoerceResult {
+  const trimmed = raw.trim();
+
+  if (trimmed === '') {
+    return {
+      kind: 'clear',
+      note: {
+        attribute: def.name,
+        from: raw,
+        to: null,
+        reason: 'cleared — the attribute is removed, not stored empty',
+      },
+    };
+  }
+
+  switch (def.type) {
+    case 'enum': {
+      const options = def.options ?? [];
+      if (!options.includes(trimmed)) {
+        return {
+          kind: 'error',
+          message: `${where}: "${def.name}"=${JSON.stringify(trimmed)} is not one of ${JSON.stringify(options)}`,
+        };
+      }
+      return { kind: 'value', value: trimmed };
+    }
+    case 'number':
+    case 'integer': {
+      const n = Number(trimmed);
+      if (!Number.isFinite(n)) {
+        return {
+          kind: 'error',
+          message: `${where}: "${def.name}" must be a number, got ${JSON.stringify(raw)}`,
+        };
+      }
+      if (def.type === 'integer' && !Number.isInteger(n)) {
+        return { kind: 'error', message: `${where}: "${def.name}" must be an integer` };
+      }
+      if (def.minimum !== undefined && n < def.minimum) {
+        return {
+          kind: 'error',
+          message: `${where}: "${def.name}" below minimum ${def.minimum}`,
+        };
+      }
+      if (def.maximum !== undefined && n > def.maximum) {
+        return {
+          kind: 'error',
+          message: `${where}: "${def.name}" above maximum ${def.maximum}`,
+        };
+      }
+      // 6% of the old catalog stored numbers as strings like "15.800000".
+      // Reporting the reparse is how a contributor learns the value is typed.
+      return String(n) === raw
+        ? { kind: 'value', value: n }
+        : {
+            kind: 'value',
+            value: n,
+            note: {
+              attribute: def.name,
+              from: raw,
+              to: n,
+              reason: `stored as the number ${n}, not the text ${JSON.stringify(raw.trim())}`,
+            },
+          };
+    }
+    case 'boolean': {
+      if (trimmed === 'true') return { kind: 'value', value: true };
+      if (trimmed === 'false') return { kind: 'value', value: false };
+      return { kind: 'error', message: `${where}: "${def.name}" must be a boolean` };
+    }
+    case 'string':
+    default:
+      return trimmed === raw
+        ? { kind: 'value', value: trimmed }
+        : {
+            kind: 'value',
+            value: trimmed,
+            note: {
+              attribute: def.name,
+              from: raw,
+              to: trimmed,
+              reason: 'surrounding whitespace removed',
+            },
+          };
+  }
+}
+```
+
+- [ ] **Step 4: Write the failing validation-mirror tests**
+
+Create `src/utils/__tests__/templateValidate.test.ts`:
+
+```ts
+import camry from './fixtures/toyota_camry_2020.json';
+import { vehicleVocab } from './fixtures/vehicleVocab';
+import { validateDraft } from '../templateValidate';
+import { addTrim, setTrimValue, renameTrim, setSelectors } from '../templateGrid';
+import type { Template } from '@/types/template';
+
+const t = camry as unknown as Template;
+
+describe('validateDraft', () => {
+  it('passes the real Camry', () => {
+    expect(validateDraft(t, vehicleVocab)).toEqual([]);
+  });
+
+  it('reports a selector-less trim on a multi-trim template, in the worker words', () => {
+    const withNew = addTrim(t, 'XLE V6');
+    expect(validateDraft(withNew, vehicleVocab)).toContain(
+      'trim XLE V6: selectors are required — a template with more than one trim cannot have a ' +
+        'selector-less trim, which would match every signal and make every decode ambiguous',
+    );
+  });
+
+  it.each([[{}], [{ manufacturerCode: [''] }], [{ vinPattern: '   ' }]])(
+    'treats the degenerate selector %p as no selector at all',
+    (selectors) => {
+      const withNew = setSelectors(
+        addTrim(t, 'XLE V6'),
+        t.trims.length,
+        selectors as never,
+      );
+      expect(
+        validateDraft(withNew, vehicleVocab).some((e) =>
+          e.includes('selectors are required'),
+        ),
+      ).toBe(true);
+    },
+  );
+
+  it('accepts a selector-less trim when it is the only trim', () => {
+    const single = { ...t, trims: [{ name: 'LE', attributes: {} }] } as Template;
+    expect(validateDraft(single, vehicleVocab)).toEqual([]);
+  });
+
+  it('reports an attribute on both the template and a trim', () => {
+    const both = {
+      ...t,
+      attributes: { ...t.attributes, powertrain_type: 'ICE' },
+    } as Template;
+    expect(validateDraft(both, vehicleVocab)).toContain(
+      '"powertrain_type" is on both the template and trim LE — pick one',
+    );
+  });
+
+  it('reports duplicate trim names and duplicate manufacturer codes', () => {
+    const dupName = renameTrim(t, 1, t.trims[0].name);
+    expect(validateDraft(dupName, vehicleVocab)).toContain(
+      `duplicate trim name "${t.trims[0].name}" — trim names must be unique`,
+    );
+
+    const code = t.trims[0].selectors!.manufacturerCode![0];
+    const dupCode = setSelectors(t, 1, { manufacturerCode: [code] });
+    expect(validateDraft(dupCode, vehicleVocab)).toContain(
+      `manufacturerCode ${code} is claimed by both "${t.trims[0].name}" and "${t.trims[1].name}"`,
+    );
+  });
+
+  it('reports an unnamed trim, an empty trims array, and an id/year disagreement', () => {
+    expect(validateDraft(renameTrim(t, 0, ''), vehicleVocab)).toContain(
+      'each trim needs a name',
+    );
+    expect(validateDraft({ ...t, trims: [] } as Template, vehicleVocab)).toContain(
+      'trims must contain at least one trim',
+    );
+    expect(validateDraft({ ...t, year: 2021 } as Template, vehicleVocab)).toContain(
+      'year 2021 does not match the year in id "toyota_camry_2020"',
+    );
+  });
+
+  it('reports an out-of-vocabulary value with the trim named', () => {
+    const bad = setTrimValue(t, 0, 'mpg_city', 400);
+    expect(validateDraft(bad, vehicleVocab)).toContain(
+      'trim LE: "mpg_city" above maximum 200',
+    );
+  });
+
+  it('says nothing about hardwareTemplateId, which is not a vocabulary attribute', () => {
+    const hw = { ...t, hardwareTemplateId: '130' } as Template;
+    expect(
+      validateDraft(hw, vehicleVocab).some((e) => e.includes('hardwareTemplateId')),
+    ).toBe(false);
+  });
+});
+```
+
+- [ ] **Step 5: Run and watch it fail**
+
+Run: `npx jest src/utils/__tests__/templateValidate.test.ts`
+Expected: FAIL — module not found.
+
+- [ ] **Step 6: Implement the mirror**
+
+Create `src/utils/templateValidate.ts`:
+
+```ts
+import type {
+  AttributeDef,
+  AttributeValue,
+  DeviceType,
+  Template,
+} from '@/types/template';
+import { hasEffectiveSelector } from '@/utils/templateGrid';
+
+const ID_RE = /^[a-z0-9][a-z0-9._&+-]*_[a-z0-9._&+-]+_[0-9]{4}$/;
+
+/**
+ * A mirror of definitions-worker/src/template.ts validateTemplate, restricted to
+ * the faults a person editing in Console can actually cause. It is NOT
+ * authoritative -- the worker is, and the save path surfaces its 422 verbatim.
+ * Its job is to stop a doomed save and to name the fault in the same words the
+ * worker would, so nobody has to reconcile two vocabularies for one problem.
+ *
+ * When the worker's strings change, this file is the drift point. The strings
+ * below are copied verbatim from definitions-worker/src/template.ts; the tests
+ * in __tests__/templateValidate.test.ts are what catch the drift.
+ */
+export function validateDraft(template: Template, vocab: DeviceType): string[] {
+  const errs: string[] = [];
+  const vmap = new Map<string, AttributeDef>(vocab.attributes.map((a) => [a.name, a]));
+
+  if (!ID_RE.test(template.id)) errs.push('id must be <make>_<model>_<year>');
+  if (!template.model) errs.push('model is required');
+  if (ID_RE.test(template.id)) {
+    const idYear = Number(template.id.split('_').at(-1));
+    if (idYear !== template.year) {
+      errs.push(`year ${template.year} does not match the year in id "${template.id}"`);
+    }
+  }
+  if (!template.manufacturer?.slug || !template.manufacturer?.name) {
+    errs.push('manufacturer requires slug and name');
+  }
+  if (
+    template.hardwareTemplateId !== undefined &&
+    !/^[0-9]+$/.test(template.hardwareTemplateId)
+  ) {
+    errs.push('hardwareTemplateId must be a numeric string');
+  }
+
+  const templateAttrs = template.attributes ?? {};
+  checkAttributes(templateAttrs, vmap, 'template', errs);
+
+  if (!Array.isArray(template.trims) || template.trims.length === 0) {
+    errs.push('trims must contain at least one trim');
+    return errs;
+  }
+
+  const multiTrim = template.trims.length > 1;
+  const seenNames = new Set<string>();
+  const seenCodes = new Map<string, string>();
+
+  for (const trim of template.trims) {
+    const name = trim.name || '';
+    if (!name) errs.push('each trim needs a name');
+    if (name) {
+      if (seenNames.has(name))
+        errs.push(`duplicate trim name "${name}" — trim names must be unique`);
+      else seenNames.add(name);
+    }
+
+    const trimAttrs = trim.attributes ?? {};
+    checkAttributes(trimAttrs, vmap, `trim ${name || '?'}`, errs);
+    for (const k of Object.keys(trimAttrs)) {
+      if (k in templateAttrs)
+        errs.push(`"${k}" is on both the template and trim ${name} — pick one`);
+    }
+
+    for (const code of trim.selectors?.manufacturerCode ?? []) {
+      const prev = seenCodes.get(code);
+      if (prev !== undefined)
+        errs.push(`manufacturerCode ${code} is claimed by both "${prev}" and "${name}"`);
+      else seenCodes.set(code, name);
+    }
+
+    if (multiTrim && !hasEffectiveSelector(trim.selectors)) {
+      errs.push(
+        `trim ${name || '?'}: selectors are required — a template with more than one trim cannot ` +
+          'have a selector-less trim, which would match every signal and make every decode ambiguous',
+      );
+    }
+  }
+
+  return errs;
+}
+
+function checkAttributes(
+  map: Record<string, AttributeValue>,
+  vmap: Map<string, AttributeDef>,
+  where: string,
+  errs: string[],
+): void {
+  for (const [k, v] of Object.entries(map)) {
+    const def = vmap.get(k);
+    if (!def) {
+      errs.push(`${where}: unknown attribute "${k}"`);
+      continue;
+    }
+    if (v === null || v === undefined || v === '' || v === '<nil>') {
+      errs.push(`${where}: "${k}" is empty — omit the attribute instead`);
+      continue;
+    }
+    switch (def.type) {
+      case 'enum':
+        if (typeof v !== 'string' || !(def.options ?? []).includes(v)) {
+          errs.push(
+            `${where}: "${k}"=${JSON.stringify(v)} is not one of ${JSON.stringify(def.options ?? [])}`,
+          );
+        }
+        break;
+      case 'number':
+      case 'integer':
+        if (typeof v !== 'number' || !Number.isFinite(v)) {
+          errs.push(`${where}: "${k}" must be a number, got ${JSON.stringify(v)}`);
+        } else if (def.type === 'integer' && !Number.isInteger(v)) {
+          errs.push(`${where}: "${k}" must be an integer`);
+        } else if (def.minimum !== undefined && v < def.minimum) {
+          errs.push(`${where}: "${k}" below minimum ${def.minimum}`);
+        } else if (def.maximum !== undefined && v > def.maximum) {
+          errs.push(`${where}: "${k}" above maximum ${def.maximum}`);
+        }
+        break;
+      case 'boolean':
+        if (typeof v !== 'boolean') errs.push(`${where}: "${k}" must be a boolean`);
+        break;
+      case 'string':
+        if (typeof v !== 'string') errs.push(`${where}: "${k}" must be a string`);
+        break;
+    }
+  }
+}
+```
+
+- [ ] **Step 7: Run both suites**
+
+Run: `npx jest src/utils/__tests__ && npm run compile`
+Expected: PASS; typecheck clean.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add src/utils/templateCoerce.ts src/utils/templateValidate.ts src/utils/__tests__/
+git commit -m "feat(templates): typed coercion, normalisation report, validation mirror
+
+Every difference between what someone types and what gets stored produces a
+Normalisation the editor shows before save -- a reparsed number, trimmed
+whitespace, a cleared attribute that removes the key. The validation mirror
+uses the worker's own error strings so one fault is never described two ways;
+it is explicitly not authoritative, and the save path still surfaces the
+worker's 422 verbatim."
+```
+
+---
+
+### Task 7: The grid
+
+The signature of the design: **agreement recedes, difference advances.** Trims
+are columns, attributes are rows, values shared across trims render muted, and
+values that differ render at full contrast. On the real Camry the eye lands on
+`powertrain_type` and `fuel_tank_capacity_gal` — the exact pair the production
+record blended. This is the inverse of normal form emphasis and it is the point.
+
+**Interactive prototype:** https://claude.ai/code/artifact/86e47b18-10ed-43cb-b65f-0760f7521615 —
+built on the real ten-trim Camry. Read it before writing the component; it is
+the reference for spacing, contrast and the rail.
+
+Three supporting devices, each encoding a contract rule rather than decorating:
+the **divergence rail** (a count, offering _Move to shared_ at 1, because that is
+the correct action under the template-or-trim rule); **trim codes in mono**
+(the model keys trims on `manufacturerCode`, so it reads as an identifier, and a
+trim without one shows `no selector` in the error colour — gate ④ as a
+validation state rather than a discovery at save); and **`—` for not set**,
+which is a different thing from empty.
+
+**Files:**
+
+- Create: `src/components/TemplateEditor/TrimGrid/TrimGrid.tsx`, `index.ts`
+- Create: `src/components/TemplateEditor/TrimGrid/TemplateCell.tsx`
+- Create: `src/components/TemplateEditor/TrimGrid/TrimHeader.tsx`
+- Create: `src/components/TemplateEditor/DivergenceRail/DivergenceRail.tsx`, `index.ts`
+- Test: `src/components/TemplateEditor/__tests__/TrimGrid.test.tsx`
+
+**Interfaces:**
+
+- Consumes: `buildGrid`, `liftToShared`, `setShared`, `clearShared`, `setTrimValue`, `clearTrimValue`, `hasEffectiveSelector` from `@/utils/templateGrid`; `coerce`, `Normalisation` from `@/utils/templateCoerce`.
+- Produces: `<TrimGrid template vocab readOnly? onChange onNormalise />` where `onChange: (next: Template) => void` and `onNormalise: (note: Normalisation) => void`.
+
+- [ ] **Step 1: Write the failing grid tests**
+
+Create `src/components/TemplateEditor/__tests__/TrimGrid.test.tsx`:
+
+```tsx
+import { render, screen, fireEvent, within } from '@testing-library/react';
+import camry from '@/utils/__tests__/fixtures/toyota_camry_2020.json';
+import { vehicleVocab } from '@/utils/__tests__/fixtures/vehicleVocab';
+import { TrimGrid } from '@/components/TemplateEditor/TrimGrid';
+import type { Template } from '@/types/template';
+
+const t = camry as unknown as Template;
+const noop = () => {};
+
+const renderGrid = (props: Partial<React.ComponentProps<typeof TrimGrid>> = {}) =>
+  render(
+    <TrimGrid
+      template={t}
+      vocab={vehicleVocab}
+      onChange={noop}
+      onNormalise={noop}
+      {...props}
+    />,
+  );
+
+describe('TrimGrid', () => {
+  it('gives every trim a column and every vocabulary attribute a row', () => {
+    renderGrid();
+    t.trims.forEach((trim) =>
+      expect(
+        screen.getByRole('columnheader', { name: new RegExp(trim.name) }),
+      ).toBeInTheDocument(),
+    );
+    vehicleVocab.attributes.forEach((a) =>
+      expect(
+        screen.getByRole('rowheader', { name: new RegExp(a.label) }),
+      ).toBeInTheDocument(),
+    );
+  });
+
+  it('mutes agreement and advances difference', () => {
+    renderGrid();
+    // powertrain_type differs across the Camry's ten trims: full contrast.
+    const diverging = screen.getByTestId('cell-powertrain_type-0');
+    expect(diverging.className).toContain('text-white');
+    expect(diverging.className).not.toContain('text-white/');
+    // number_of_doors is shared by every trim: muted.
+    expect(screen.getByTestId('shared-number_of_doors').className).toContain(
+      'text-white/40',
+    );
+  });
+
+  it('shows an em dash, not an empty cell, where nothing is set', () => {
+    renderGrid();
+    const cell = screen.getByTestId('shared-emissions_standard');
+    expect(cell).toHaveTextContent('—');
+    expect(cell.className).toContain('text-white/25');
+  });
+
+  it('reads the divergence count off the rail, and offers no lift while trims disagree', () => {
+    renderGrid();
+    expect(screen.getByTestId('rail-powertrain_type')).toHaveTextContent('2');
+    expect(
+      within(screen.getByTestId('rail-powertrain_type')).queryByRole('button'),
+    ).toBeNull();
+  });
+
+  it('offers Move to shared once every trim agrees, and lifts on click', () => {
+    const onChange = jest.fn();
+    const agreed = {
+      ...t,
+      attributes: {},
+      trims: t.trims.map((trim) => ({
+        ...trim,
+        attributes: { ...trim.attributes, number_of_doors: 4 },
+      })),
+    } as Template;
+    render(
+      <TrimGrid
+        template={agreed}
+        vocab={vehicleVocab}
+        onChange={onChange}
+        onNormalise={noop}
+      />,
+    );
+    fireEvent.click(
+      within(screen.getByTestId('rail-number_of_doors')).getByRole('button', {
+        name: /move to shared/i,
+      }),
+    );
+    expect(onChange).toHaveBeenCalledWith(
+      expect.objectContaining({
+        attributes: expect.objectContaining({ number_of_doors: 4 }),
+      }),
+    );
+  });
+
+  it('marks a trim with no effective selector, which is gate 4', () => {
+    const broken = {
+      ...t,
+      trims: [
+        ...t.trims,
+        { name: 'XLE V6', attributes: {}, selectors: { manufacturerCode: [''] } },
+      ],
+    } as Template;
+    render(
+      <TrimGrid
+        template={broken}
+        vocab={vehicleVocab}
+        onChange={noop}
+        onNormalise={noop}
+      />,
+    );
+    const header = screen.getByRole('columnheader', { name: /XLE V6/ });
+    expect(header).toHaveTextContent('no selector');
+    expect(within(header).getByText('no selector').className).toContain('text-red-400');
+  });
+
+  it('offers exactly the vocabulary options for an enum, plus not set', () => {
+    renderGrid();
+    const select = within(screen.getByTestId('cell-powertrain_type-0')).getByRole(
+      'combobox',
+    );
+    expect(
+      within(select)
+        .getAllByRole('option')
+        .map((o) => o.textContent),
+    ).toEqual(['—', 'ICE', 'HEV', 'PHEV', 'BEV', 'FCEV']);
+  });
+
+  it('types a value, reports the reparse, and never stores the text', () => {
+    const onChange = jest.fn();
+    const onNormalise = jest.fn();
+    render(
+      <TrimGrid
+        template={t}
+        vocab={vehicleVocab}
+        onChange={onChange}
+        onNormalise={onNormalise}
+      />,
+    );
+    const input = within(screen.getByTestId('cell-fuel_tank_capacity_gal-0')).getByRole(
+      'textbox',
+    );
+    fireEvent.change(input, { target: { value: '15.800000' } });
+    fireEvent.blur(input);
+    expect(onChange.mock.calls[0][0].trims[0].attributes.fuel_tank_capacity_gal).toBe(
+      15.8,
+    );
+    expect(onNormalise).toHaveBeenCalledWith(
+      expect.objectContaining({ attribute: 'fuel_tank_capacity_gal', to: 15.8 }),
+    );
+  });
+
+  it('clearing a cell removes the attribute and says so', () => {
+    const onChange = jest.fn();
+    const onNormalise = jest.fn();
+    render(
+      <TrimGrid
+        template={t}
+        vocab={vehicleVocab}
+        onChange={onChange}
+        onNormalise={onNormalise}
+      />,
+    );
+    const input = within(screen.getByTestId('cell-mpg_city-0')).getByRole('textbox');
+    fireEvent.change(input, { target: { value: '' } });
+    fireEvent.blur(input);
+    expect('mpg_city' in onChange.mock.calls[0][0].trims[0].attributes).toBe(false);
+    expect(onNormalise).toHaveBeenCalledWith(expect.objectContaining({ to: null }));
+  });
+
+  it('refuses an out-of-range value in the worker words and does not change the template', () => {
+    const onChange = jest.fn();
+    render(
+      <TrimGrid
+        template={t}
+        vocab={vehicleVocab}
+        onChange={onChange}
+        onNormalise={noop}
+      />,
+    );
+    const cell = screen.getByTestId('cell-mpg_city-0');
+    fireEvent.change(within(cell).getByRole('textbox'), { target: { value: '400' } });
+    fireEvent.blur(within(cell).getByRole('textbox'));
+    expect(onChange).not.toHaveBeenCalled();
+    expect(cell).toHaveTextContent('trim LE: "mpg_city" above maximum 200');
+  });
+
+  it('renders no inputs when read only', () => {
+    renderGrid({ readOnly: true });
+    expect(screen.queryAllByRole('textbox')).toHaveLength(0);
+    expect(screen.queryAllByRole('combobox')).toHaveLength(0);
+  });
+});
+```
+
+- [ ] **Step 2: Run and watch it fail**
+
+Run: `npx jest src/components/TemplateEditor`
+Expected: FAIL — module not found.
+
+- [ ] **Step 3: Implement `TrimHeader`**
+
+Create `src/components/TemplateEditor/TrimGrid/TrimHeader.tsx`:
+
+```tsx
+import React, { type FC } from 'react';
+import type { Trim } from '@/types/template';
+import { hasEffectiveSelector } from '@/utils/templateGrid';
+
+interface Props {
+  trim: Trim;
+  multiTrim: boolean;
+}
+
+/**
+ * The model keys trims on manufacturerCode, so the code reads as an identifier
+ * and gets mono. A trim without an effective selector on a multi-trim template
+ * makes every decode for the model-year ambiguous; the worker refuses it, and
+ * showing that here is the difference between a validation state and a
+ * discovery at save.
+ */
+export const TrimHeader: FC<Props> = ({ trim, multiTrim }) => {
+  const code = trim.selectors?.manufacturerCode?.find((c) => c.trim().length > 0);
+  const style = trim.selectors?.styleName?.find((s) => s.trim().length > 0);
+  const missing = multiTrim && !hasEffectiveSelector(trim.selectors);
+
+  return (
+    <div className="flex min-w-[9rem] flex-col gap-0.5 px-3 py-2 text-left">
+      <span className="text-white">{trim.name}</span>
+      {missing ? (
+        <span className="font-mono text-xs text-red-400">no selector</span>
+      ) : (
+        <span className="font-mono text-xs text-white/50">
+          {code ?? style ?? trim.selectors?.vinPattern}
+        </span>
+      )}
+    </div>
+  );
+};
+```
+
+- [ ] **Step 4: Implement `DivergenceRail`**
+
+Create `src/components/TemplateEditor/DivergenceRail/DivergenceRail.tsx`:
+
+```tsx
+import React, { type FC } from 'react';
+import type { GridRow } from '@/utils/templateGrid';
+
+interface Props {
+  row: GridRow;
+  readOnly?: boolean;
+  onLift: (name: string) => void;
+}
+
+/**
+ * How many distinct values this attribute holds across the trims. At 1 with the
+ * attribute still living on the trims, the correct modelling action under the
+ * template-or-trim rule is to move it up -- so that is what the rail offers,
+ * rather than a generic edit affordance.
+ */
+export const DivergenceRail: FC<Props> = ({ row, readOnly, onLift }) => {
+  if (row.scope === 'absent') return <span className="text-white/25">·</span>;
+  if (row.scope === 'shared') return <span className="text-white/40">shared</span>;
+
+  return (
+    <span className="flex items-center gap-2">
+      <span
+        className={
+          row.distinct > 1 ? 'tabular-nums text-white' : 'tabular-nums text-white/50'
+        }
+      >
+        {row.distinct}
+      </span>
+      {row.canLift && !readOnly && (
+        <button
+          type="button"
+          onClick={() => onLift(row.def.name)}
+          className="rounded-full border border-cta-default px-2 py-0.5 text-xs text-white/70 hover:border-white hover:text-white"
+        >
+          Move to shared
+        </button>
+      )}
+    </span>
+  );
+};
+```
+
+Create `src/components/TemplateEditor/DivergenceRail/index.ts`:
+
+```ts
+export * from './DivergenceRail';
+```
+
+- [ ] **Step 5: Implement `TemplateCell`**
+
+Create `src/components/TemplateEditor/TrimGrid/TemplateCell.tsx`:
+
+```tsx
+import React, { useState, type FC } from 'react';
+import classnames from 'classnames';
+import type { AttributeDef, AttributeValue } from '@/types/template';
+import { coerce, type Normalisation } from '@/utils/templateCoerce';
+
+interface Props {
+  def: AttributeDef;
+  value: AttributeValue | undefined;
+  where: string;
+  emphasised: boolean;
+  readOnly?: boolean;
+  testId: string;
+  onSet: (value: AttributeValue) => void;
+  onClear: () => void;
+  onNormalise: (note: Normalisation) => void;
+}
+
+const NOT_SET = '—';
+
+export const TemplateCell: FC<Props> = ({
+  def,
+  value,
+  where,
+  emphasised,
+  readOnly,
+  testId,
+  onSet,
+  onClear,
+  onNormalise,
+}) => {
+  const [draft, setDraft] = useState<string>(value === undefined ? '' : String(value));
+  const [error, setError] = useState<string | null>(null);
+
+  // Agreement recedes, difference advances. There is no light font weight in
+  // this design system, so emphasis rides entirely on opacity.
+  const tone =
+    value === undefined ? 'text-white/25' : emphasised ? 'text-white' : 'text-white/40';
+
+  const commit = (raw: string) => {
+    const result = coerce(def, raw, where);
+    if (result.kind === 'error') {
+      setError(result.message);
+      return;
+    }
+    setError(null);
+    if (result.note) onNormalise(result.note);
+    if (result.kind === 'clear') {
+      setDraft('');
+      onClear();
+      return;
+    }
+    setDraft(String(result.value));
+    onSet(result.value);
+  };
+
+  if (readOnly) {
+    return (
+      <div data-testid={testId} className={classnames('px-3 py-2', tone)}>
+        {value === undefined ? NOT_SET : String(value)}
+      </div>
+    );
+  }
+
+  return (
+    <div data-testid={testId} className={classnames('px-2 py-1.5', tone)}>
+      {def.type === 'enum' || def.type === 'boolean' ? (
+        <select
+          aria-label={`${where} ${def.label}`}
+          value={draft}
+          onChange={(e) => {
+            setDraft(e.target.value);
+            commit(e.target.value);
+          }}
+          className={classnames('w-full rounded-md bg-dark-grey-950 px-2 py-1', tone)}
+        >
+          <option value="">{NOT_SET}</option>
+          {(def.type === 'boolean' ? ['true', 'false'] : (def.options ?? [])).map((o) => (
+            <option key={o} value={o}>
+              {o}
+            </option>
+          ))}
+        </select>
+      ) : (
+        <input
+          type="text"
+          inputMode={def.type === 'string' ? 'text' : 'decimal'}
+          aria-label={`${where} ${def.label}`}
+          placeholder={NOT_SET}
+          value={draft}
+          onChange={(e) => setDraft(e.target.value)}
+          onBlur={(e) => commit(e.target.value)}
+          className={classnames('w-full rounded-md bg-dark-grey-950 px-2 py-1', tone)}
+        />
+      )}
+      {error && <p className="pt-1 text-xs text-red-400">{error}</p>}
+    </div>
+  );
+};
+```
+
+- [ ] **Step 6: Implement `TrimGrid`**
+
+Create `src/components/TemplateEditor/TrimGrid/TrimGrid.tsx`:
+
+```tsx
+import React, { type FC } from 'react';
+import type { DeviceType, Template } from '@/types/template';
+import type { Normalisation } from '@/utils/templateCoerce';
+import {
+  buildGrid,
+  clearShared,
+  clearTrimValue,
+  liftToShared,
+  setShared,
+  setTrimValue,
+} from '@/utils/templateGrid';
+import { DivergenceRail } from '@/components/TemplateEditor/DivergenceRail';
+import { TemplateCell } from './TemplateCell';
+import { TrimHeader } from './TrimHeader';
+
+export interface TrimGridProps {
+  template: Template;
+  vocab: DeviceType;
+  readOnly?: boolean;
+  onChange: (next: Template) => void;
+  onNormalise: (note: Normalisation) => void;
+}
+
+export const TrimGrid: FC<TrimGridProps> = ({
+  template,
+  vocab,
+  readOnly,
+  onChange,
+  onNormalise,
+}) => {
+  const grid = buildGrid(template, vocab);
+  const multiTrim = template.trims.length > 1;
+
+  return (
+    <div className="overflow-x-auto rounded-xl border border-cta-default bg-surface-default">
+      <table className="w-full border-collapse text-sm">
+        <thead>
+          <tr className="bg-surface-sunken">
+            <th
+              scope="col"
+              className="sticky left-0 z-10 bg-surface-sunken px-3 py-2 text-left text-white/50"
+            >
+              Attribute
+            </th>
+            <th scope="col" className="px-3 py-2 text-left text-white/50">
+              Values
+            </th>
+            {template.trims.map((trim, i) => (
+              <th
+                key={`${trim.name}-${i}`}
+                scope="col"
+                className="border-l border-cta-default align-top"
+              >
+                <TrimHeader trim={trim} multiTrim={multiTrim} />
+              </th>
+            ))}
+          </tr>
+        </thead>
+        <tbody>
+          {grid.rows.map((row) => (
+            <tr key={row.def.name} className="border-t border-cta-default">
+              <th
+                scope="row"
+                className="sticky left-0 z-10 bg-surface-default px-3 py-2 text-left font-normal text-white/70"
+              >
+                {row.def.label}
+                {row.def.unit && (
+                  <span className="pl-1 text-white/40">({row.def.unit})</span>
+                )}
+              </th>
+              <td data-testid={`rail-${row.def.name}`} className="px-3 py-2">
+                <DivergenceRail
+                  row={row}
+                  readOnly={readOnly}
+                  onLift={(n) => onChange(liftToShared(template, n))}
+                />
+              </td>
+              {row.scope === 'trim' ? (
+                template.trims.map((trim, i) => (
+                  <td
+                    key={`${trim.name}-${i}`}
+                    className="border-l border-cta-default align-top"
+                  >
+                    <TemplateCell
+                      def={row.def}
+                      value={row.cells[i]}
+                      where={`trim ${trim.name || '?'}`}
+                      emphasised={row.distinct > 1}
+                      readOnly={readOnly}
+                      testId={`cell-${row.def.name}-${i}`}
+                      onSet={(v) => onChange(setTrimValue(template, i, row.def.name, v))}
+                      onClear={() => onChange(clearTrimValue(template, i, row.def.name))}
+                      onNormalise={onNormalise}
+                    />
+                  </td>
+                ))
+              ) : (
+                // One value, stated once, spanning every trim -- the visual form
+                // of "this is true of the whole model-year".
+                <td
+                  colSpan={template.trims.length}
+                  className="border-l border-cta-default align-top"
+                >
+                  <TemplateCell
+                    def={row.def}
+                    value={row.shared}
+                    where="template"
+                    emphasised={false}
+                    readOnly={readOnly}
+                    testId={`shared-${row.def.name}`}
+                    onSet={(v) => onChange(setShared(template, row.def.name, v))}
+                    onClear={() => onChange(clearShared(template, row.def.name))}
+                    onNormalise={onNormalise}
+                  />
+                </td>
+              )}
+            </tr>
+          ))}
+        </tbody>
+      </table>
+    </div>
+  );
+};
+```
+
+Create `src/components/TemplateEditor/TrimGrid/index.ts`:
+
+```ts
+export * from './TrimGrid';
+```
+
+- [ ] **Step 7: Run the tests**
+
+Run: `npx jest src/components/TemplateEditor && npm run compile && npm run lint`
+Expected: PASS, 12 tests; typecheck and lint clean.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add src/components/TemplateEditor
+git commit -m "feat(templates): the trim grid
+
+Trims as columns, attributes as rows, agreement muted and difference at full
+contrast -- the inverse of normal form emphasis, so the pair of attributes the
+production Camry record blended is the pair the eye lands on. The divergence
+rail offers Move to shared at one distinct value because that is the correct
+action under the template-or-trim rule, and a trim with no effective selector
+is marked in the header rather than discovered at save."
+```
+
+---
+
+### Task 8: Browse — and say what has no template
+
+**Files:**
+
+- Create: `src/app/templates/layout.ts`, `src/app/templates/page.tsx`
+- Create: `src/app/templates/templatesPage/View/View.tsx`, `index.ts`
+- Create: `src/app/templates/templatesPage/Header/Header.tsx`, `index.ts`
+- Create: `src/app/api/templates/route.ts`
+- Create: `src/hooks/queries/useTemplateSearch.ts`
+- Modify: `src/config/navigation.ts`
+- Test: `__tests__/unit/app/templatesSearchRoute.test.ts`
+
+**Interfaces:**
+
+- Consumes: `fetchTemplate` from `@/services/definitions`; identity-api at `config.identityApiUrl`.
+- Produces:
+  - `GET /api/templates?make=<name-or-slug>&model=<string>&year=<int>` → `{ manufacturer: { name, tokenId } | null, results: SearchResult[] }`
+  - `SearchResult { id: string; model: string; year: number; status: 'ok' | 'missing' | 'invalid-id'; version?: number; trims?: number }`
+  - `useTemplateSearch({ make, model, year })` → TanStack Query wrapper
+
+Three states, all real, none an error to hide:
+
+- `ok` — a template exists; show its version and trim count.
+- `missing` — the definition exists but no template has been imported. **5,152 of the emitted set carry no attributes and the import has not run in production at all**, so this is the common case, not a fault.
+- `invalid-id` — the device definition id cannot be a template id. `subaru_tribeca-(ny/nj)_2008` is live in production today and 137 ids like it fail the schema; whether to widen the pattern or correct the ids is undecided. Show it, say why it cannot be edited, and do not pretend it is missing.
+
+- [ ] **Step 1: Write the failing route test**
+
+Create `__tests__/unit/app/templatesSearchRoute.test.ts`:
+
+```ts
+import { GET } from '@/app/api/templates/route';
+import { NextRequest } from 'next/server';
+
+jest.mock('@/services/definitions', () => ({
+  fetchTemplate: jest.fn(),
+}));
+import { fetchTemplate } from '@/services/definitions';
+
+const identityResponse = {
+  data: {
+    manufacturer: {
+      name: 'Toyota',
+      tokenId: 131,
+      deviceDefinitions: {
+        nodes: [
+          { deviceDefinitionId: 'toyota_camry_2020', model: 'Camry', year: 2020 },
+          { deviceDefinitionId: 'toyota_supra_2020', model: 'Supra', year: 2020 },
+        ],
+      },
+    },
+  },
+};
+
+const req = (qs: string) => new NextRequest(`https://console.test/api/templates?${qs}`);
+
+describe('GET /api/templates', () => {
+  beforeEach(() => {
+    global.fetch = jest
+      .fn()
+      .mockResolvedValue({
+        ok: true,
+        json: async () => identityResponse,
+      }) as unknown as typeof fetch;
+  });
+
+  it('requires a make', async () => {
+    expect((await GET(req('model=Camry'))).status).toBe(400);
+  });
+
+  it('marks a definition with no template as missing rather than failing', async () => {
+    (fetchTemplate as jest.Mock)
+      .mockResolvedValueOnce({ id: 'toyota_camry_2020', version: 3, trims: [{}, {}] })
+      .mockResolvedValueOnce(null);
+    const body = await (await GET(req('make=Toyota&model=Camry&year=2020'))).json();
+    expect(body.results).toEqual([
+      {
+        id: 'toyota_camry_2020',
+        model: 'Camry',
+        year: 2020,
+        status: 'ok',
+        version: 3,
+        trims: 2,
+      },
+      { id: 'toyota_supra_2020', model: 'Supra', year: 2020, status: 'missing' },
+    ]);
+  });
+
+  it('marks an id the schema cannot accept, without asking the worker about it', async () => {
+    global.fetch = jest.fn().mockResolvedValue({
+      ok: true,
+      json: async () => ({
+        data: {
+          manufacturer: {
+            name: 'Subaru',
+            tokenId: 1,
+            deviceDefinitions: {
+              nodes: [
+                {
+                  deviceDefinitionId: 'subaru_tribeca-(ny/nj)_2008',
+                  model: 'Tribeca',
+                  year: 2008,
+                },
+              ],
+            },
+          },
+        },
+      }),
+    }) as unknown as typeof fetch;
+    (fetchTemplate as jest.Mock).mockClear();
+    const body = await (await GET(req('make=Subaru'))).json();
+    expect(body.results[0].status).toBe('invalid-id');
+    expect(fetchTemplate).not.toHaveBeenCalled();
+  });
+
+  it('reports an unknown manufacturer as null rather than an empty result set', async () => {
+    global.fetch = jest
+      .fn()
+      .mockResolvedValue({
+        ok: true,
+        json: async () => ({ data: { manufacturer: null } }),
+      }) as unknown as typeof fetch;
+    const body = await (await GET(req('make=Nope'))).json();
+    expect(body).toEqual({ manufacturer: null, results: [] });
+  });
+});
+```
+
+- [ ] **Step 2: Run and watch it fail**
+
+Run: `npx jest __tests__/unit/app/templatesSearchRoute.test.ts`
+Expected: FAIL — module not found.
+
+- [ ] **Step 3: Implement the search route**
+
+Create `src/app/api/templates/route.ts`:
+
+```ts
+import { NextRequest, NextResponse } from 'next/server';
+import config from '@/config';
+import { fetchTemplate } from '@/services/definitions';
+
+// definitions-worker/schema/template.schema.json, properties.id.pattern.
+const ID_RE = /^[a-z0-9][a-z0-9._&+-]*_[a-z0-9._&+-]+_[0-9]{4}$/;
+
+// Identity's DeviceDefinitionFilter takes model and year only, and
+// ManufacturerBy takes a name or a slug -- so "make" here is whichever the
+// person typed, tried as a slug first because that is what a template id
+// carries.
+const SEARCH = `
+  query TemplateSearch($by: ManufacturerBy!, $filterBy: DeviceDefinitionFilter, $first: Int!) {
+    manufacturer(by: $by) {
+      name
+      tokenId
+      deviceDefinitions(filterBy: $filterBy, first: $first) {
+        nodes { deviceDefinitionId model year }
+      }
+    }
+  }`;
+
+const PAGE = 25;
+
+export interface SearchResult {
+  id: string;
+  model: string;
+  year: number;
+  status: 'ok' | 'missing' | 'invalid-id';
+  version?: number;
+  trims?: number;
+}
+
+async function queryIdentity(
+  by: Record<string, string>,
+  filterBy: Record<string, unknown>,
+) {
+  const resp = await fetch(config.identityApiUrl, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ query: SEARCH, variables: { by, filterBy, first: PAGE } }),
+    cache: 'no-store',
+  });
+  if (!resp.ok) throw new Error(`identity-api returned ${resp.status}`);
+  const json = (await resp.json()) as {
+    data?: {
+      manufacturer?: {
+        name: string;
+        tokenId: number;
+        deviceDefinitions: {
+          nodes: { deviceDefinitionId: string; model: string; year: number }[];
+        };
+      } | null;
+    };
+  };
+  return json.data?.manufacturer ?? null;
+}
+
+export async function GET(req: NextRequest) {
+  const make = req.nextUrl.searchParams.get('make');
+  const model = req.nextUrl.searchParams.get('model');
+  const yearParam = req.nextUrl.searchParams.get('year');
+  if (!make) return NextResponse.json({ error: 'make is required' }, { status: 400 });
+
+  const filterBy: Record<string, unknown> = {};
+  if (model) filterBy.model = model;
+  if (yearParam) {
+    const year = Number(yearParam);
+    if (!Number.isInteger(year))
+      return NextResponse.json({ error: 'year must be an integer' }, { status: 400 });
+    filterBy.year = year;
+  }
+
+  try {
+    const manufacturer =
+      (await queryIdentity({ slug: make.toLowerCase() }, filterBy)) ??
+      (await queryIdentity({ name: make }, filterBy));
+    if (!manufacturer) return NextResponse.json({ manufacturer: null, results: [] });
+
+    const results = await Promise.all(
+      manufacturer.deviceDefinitions.nodes.map(async (node): Promise<SearchResult> => {
+        const base = { id: node.deviceDefinitionId, model: node.model, year: node.year };
+        // 137 ids in production cannot be template ids -- subaru_tribeca-(ny/nj)_2008
+        // is live today. Saying so beats asking the worker a question whose
+        // answer would be a misleading 404.
+        if (!ID_RE.test(node.deviceDefinitionId))
+          return { ...base, status: 'invalid-id' };
+        const template = await fetchTemplate(node.deviceDefinitionId);
+        // A missing template is a real state: the import has not run in
+        // production, and 5,152 of the emitted set carry no attributes.
+        if (!template) return { ...base, status: 'missing' };
+        return {
+          ...base,
+          status: 'ok',
+          version: template.version,
+          trims: template.trims.length,
+        };
+      }),
+    );
+
+    return NextResponse.json({
+      manufacturer: { name: manufacturer.name, tokenId: manufacturer.tokenId },
+      results,
+    });
+  } catch (err) {
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : 'search failed' },
+      { status: 502 },
+    );
+  }
+}
+```
+
+- [ ] **Step 4: Run the route tests**
+
+Run: `npx jest __tests__/unit/app/templatesSearchRoute.test.ts`
+Expected: PASS, 4 tests.
+
+- [ ] **Step 5: Build the page**
+
+Create `src/app/templates/layout.ts` (identical to `src/app/webhooks/layout.ts`):
+
+```ts
+import { AuthorizedLayout } from '@/layouts/AuthorizedLayout';
+
+export default AuthorizedLayout;
+```
+
+Create `src/app/templates/page.tsx`:
+
+```tsx
+'use client';
+
+import React, { Suspense, type FC } from 'react';
+
+import { TemplatesPage as View } from './templatesPage/View';
+
+const TemplatesPage: FC = () => (
+  <Suspense fallback={<div>Loading...</div>}>
+    <View />
+  </Suspense>
+);
+
+export default TemplatesPage;
+```
+
+Create `src/hooks/queries/useTemplateSearch.ts`:
+
+```ts
+'use client';
+
+import { useQuery } from '@tanstack/react-query';
+import type { SearchResult } from '@/app/api/templates/route';
+
+export interface TemplateSearch {
+  manufacturer: { name: string; tokenId: number } | null;
+  results: SearchResult[];
+}
+
+export const useTemplateSearch = (params: {
+  make: string;
+  model: string;
+  year: string;
+}) =>
+  useQuery<TemplateSearch>({
+    queryKey: ['template-search', params],
+    enabled: params.make.trim().length > 0,
+    staleTime: 30000,
+    refetchOnWindowFocus: false,
+    queryFn: async () => {
+      const qs = new URLSearchParams({ make: params.make });
+      if (params.model) qs.set('model', params.model);
+      if (params.year) qs.set('year', params.year);
+      const resp = await fetch(`/api/templates?${qs}`);
+      const json = await resp.json();
+      if (!resp.ok) throw new Error(json.error ?? 'Search failed');
+      return json as TemplateSearch;
+    },
+  });
+```
+
+Create `src/app/templates/templatesPage/Header/Header.tsx` (mirroring
+`src/app/webhooks/webhooksPage/Header/Header.tsx` — read that file and match its
+structure and copy) with the title "Vehicle templates" and the subtitle
+"One model-year, and the trims it shipped in."
+
+Create `src/app/templates/templatesPage/View/View.tsx`:
+
+```tsx
+'use client';
+
+import React, { useState } from 'react';
+import Link from 'next/link';
+import { Header } from '@/app/templates/templatesPage/Header';
+import { useTemplateSearch } from '@/hooks/queries/useTemplateSearch';
+import { QueryPageWrapper } from '@/components/QueryPageWrapper';
+import { Button } from '@/components/Button';
+
+const STATUS_COPY: Record<string, { label: string; className: string; hint: string }> = {
+  'ok': { label: 'Template', className: 'text-white', hint: '' },
+  'missing': {
+    label: 'No template yet',
+    className: 'text-white/50',
+    hint: 'This model-year exists but no template has been imported for it.',
+  },
+  'invalid-id': {
+    label: 'Id cannot be a template',
+    className: 'text-red-400',
+    hint: 'This device definition id does not match the template id pattern, so it cannot be edited until the id is corrected.',
+  },
+};
+
+export const TemplatesPage = () => {
+  const [form, setForm] = useState({ make: '', model: '', year: '' });
+  const [query, setQuery] = useState(form);
+  const { data, isLoading, error } = useTemplateSearch(query);
+
+  return (
+    <div className="flex flex-col gap-6">
+      <Header />
+
+      <form
+        className="flex flex-wrap items-end gap-3"
+        onSubmit={(e) => {
+          e.preventDefault();
+          setQuery(form);
+        }}
+      >
+        {(['make', 'model', 'year'] as const).map((field) => (
+          <label key={field} className="flex flex-col gap-1 text-white/50">
+            <span className="text-xs uppercase tracking-wide">{field}</span>
+            <input
+              value={form[field]}
+              onChange={(e) => setForm({ ...form, [field]: e.target.value })}
+              placeholder={
+                field === 'make' ? 'Toyota' : field === 'model' ? 'Camry' : '2020'
+              }
+              className="h-10 rounded-full bg-dark-grey-950 px-4 text-white placeholder:text-white/25"
+            />
+          </label>
+        ))}
+        <Button type="submit">Search</Button>
+      </form>
+
+      <QueryPageWrapper
+        loading={isLoading}
+        error={error ?? undefined}
+        customErrorMessage="There was a problem searching device definitions"
+      >
+        {data && !data.manufacturer && (
+          <p className="text-white/50">No manufacturer matched that name or slug.</p>
+        )}
+        <ul className="flex flex-col divide-y divide-cta-default rounded-xl border border-cta-default bg-surface-default">
+          {(data?.results ?? []).map((r) => (
+            <li key={r.id} className="flex items-center justify-between gap-4 px-4 py-3">
+              <div className="flex flex-col">
+                <span className="font-mono text-white">{r.id}</span>
+                <span className={`text-xs ${STATUS_COPY[r.status].className}`}>
+                  {STATUS_COPY[r.status].label}
+                  {r.status === 'ok' &&
+                    ` · v${r.version} · ${r.trims} trim${r.trims === 1 ? '' : 's'}`}
+                </span>
+                {STATUS_COPY[r.status].hint && (
+                  <span className="pt-1 text-xs text-white/40">
+                    {STATUS_COPY[r.status].hint}
+                  </span>
+                )}
+              </div>
+              {r.status !== 'invalid-id' && (
+                <Link href={`/templates/${r.id}`} className="button">
+                  {r.status === 'ok' ? 'Open' : 'Create'}
+                </Link>
+              )}
+            </li>
+          ))}
+        </ul>
+      </QueryPageWrapper>
+    </div>
+  );
+};
+```
+
+Create `src/app/templates/templatesPage/View/index.ts`:
+
+```ts
+export * from './View';
+```
+
+- [ ] **Step 6: Put it in the navigation**
+
+A page nobody can reach is not shipped. In `src/config/navigation.ts`:
+
+```ts
+import { CarRentalIcon } from '@/components/Icons';
+
+const TEMPLATE_EDIT_REGEX = /^\/templates\/[^/]+$/;
+```
+
+add to `getPageTitle`, before the final `return`:
+
+```ts
+if (path === '/templates/new') return 'New template';
+if (TEMPLATE_EDIT_REGEX.test(path)) return 'Edit template';
+```
+
+add to `pageTitles`:
+
+```ts
+  '/templates': 'Vehicle templates',
+```
+
+and add to `baseMainMenu`, immediately after the Webhooks entry:
+
+```ts
+  {
+    label: 'Templates',
+    icon: CarRentalIcon,
+    iconClassName: 'h-5 w-5',
+    link: '/templates',
+    external: false,
+    disabled: false,
+  },
+```
+
+Note the ordering: `'/templates/new'` is checked before `TEMPLATE_EDIT_REGEX`,
+which would otherwise match it and title the create page "Edit template".
+
+- [ ] **Step 7: Verify and commit**
+
+Run: `npm test && npm run compile && npm run lint`
+Expected: full suite green, typecheck and lint clean.
+
+```bash
+git add src/app/templates src/app/api/templates/route.ts src/hooks/queries/useTemplateSearch.ts \
+  src/config/navigation.ts __tests__/unit/app/templatesSearchRoute.test.ts
+git commit -m "feat(templates): browse device definitions and their template state
+
+Three states, all real. A definition with no template says so rather than
+erroring -- the import has not run in production and 5,152 of the emitted set
+carry no attributes. An id the schema cannot accept says that instead, because
+137 of them are live today and subaru_tribeca-(ny/nj)_2008 is one."
+```
+
+---
+
+# Phase 2 — the write path (repo: `dimo-developer-console`)
+
+---
+
+### Task 9: The server route — gate ①
+
+The worker authenticates with a single shared `WRITE_TOKEN` and `author` is
+client-suppliable and unverified. Console must never hold that token in the
+browser and must never let a caller name themselves. This route is where both
+facts get fixed: it holds the token server-side, identifies the caller from the
+existing session, **stamps `author` from that session**, and resolves what the
+caller is entitled to do before it forwards anything.
+
+`src/middleware.ts` already 401s an unauthenticated `/api/*` request. That is a
+first line, not the authorization — the route still resolves its own caller,
+because a middleware matcher is a configuration file and this is a guarantee.
+
+**Files:**
+
+- Create: `src/services/templateEntitlement.ts`
+- Create: `src/app/api/templates/[id]/route.ts`
+- Test: `__tests__/unit/services/templateEntitlement.test.ts`
+- Test: `__tests__/unit/app/templateRoute.test.ts`
+
+**Interfaces:**
+
+- Consumes: `getUserByToken` from `@/services/user`; `getUserSubOrganization` from `@/services/globalAccount`; `fetchTemplate`, `fetchVocabulary`, `publishTemplate` from `@/services/definitions`.
+- Produces:
+  - `resolveCaller(): Promise<{ address: \`0x${string}\`; email: string } | null>`
+  - `countMintedVehicles(id: string): Promise<number>`
+  - `manufacturerOwner(slug: string): Promise<{ owner: string; tokenId: number } | null>`
+  - `resolveEntitlement(args): Promise<Entitlement>` and `Entitlement` (Step 2)
+  - `GET /api/templates/[id]` → `{ template: Template | null, vocabulary: DeviceType, entitlement: Entitlement }`
+  - `PUT /api/templates/[id]` → `{ template }` | `{ errors }` (422) | `{ conflict }` (409) | `{ error, entitlement }` (403)
+
+**Contribution model, as implemented**
+
+| Situation                                                                  | Who may publish               | Tier                                              |
+| -------------------------------------------------------------------------- | ----------------------------- | ------------------------------------------------- |
+| No template at this id                                                     | any signed-in account         | `create`                                          |
+| Template exists, 0 minted vehicles, `author` absent or equal to the caller | that account                  | `author`                                          |
+| Template exists, ≥1 minted vehicle, caller holds the Manufacturer NFT      | that account                  | `manufacturer`                                    |
+| Caller address is in `DIMO_CURATOR_ADDRESSES`                              | always                        | `curator`                                         |
+| Anything else                                                              | nobody, yet                   | `proposal-required` — 403, editor stays read-only |
+| `hardwareTemplateId` changes                                               | `curator` only, at every tier | 403 otherwise                                     |
+
+**There is deliberately no UI for setting `hardwareTemplateId`.** The route
+permits a curator to change it so an admin client can, but the editor never
+renders a field for it — a control nobody but DIMO may use is a control that
+invites the wrong person to try it, and the value is set today by
+`common/utils.go:202` for every definition. `EntitlementBanner` says so out
+loud instead.
+
+> **Assumption to confirm with Yev before merge.** The spec's row reads "Edit a
+> template nothing references yet | _its author_". Most templates in the catalog
+> come from the backfill and carry no `author` at all, which under a literal
+> reading would make every one of them uneditable by anyone but a curator. This
+> implementation treats an **absent** `author` as unowned, so any signed-in
+> account may edit an unreferenced, unauthored template. A template with a
+> different author still requires a proposal. If that is wrong, the single
+> change is in `resolveEntitlement`.
+
+- [ ] **Step 1: Write the failing entitlement tests**
+
+Create `__tests__/unit/services/templateEntitlement.test.ts`:
+
+```ts
+import { resolveEntitlement } from '@/services/templateEntitlement';
+import type { Template } from '@/types/template';
+
+const CALLER = '0x1111111111111111111111111111111111111111';
+const OTHER = '0x2222222222222222222222222222222222222222';
+const CURATOR = '0x3333333333333333333333333333333333333333';
+
+const template = (over: Partial<Template> = {}) =>
+  ({
+    id: 'toyota_camry_2020',
+    deviceType: 'vehicle',
+    manufacturer: { slug: 'toyota', name: 'Toyota', tokenId: 131 },
+    model: 'Camry',
+    year: 2020,
+    attributes: {},
+    trims: [{ name: 'LE', attributes: {} }],
+    version: 3,
+    createdAt: '2026-08-01T00:00:00.000Z',
+    updatedAt: '2026-08-01T00:00:00.000Z',
+    ...over,
+  }) as Template;
+
+const deps = (minted: number, owner: string | null) => ({
+  countMintedVehicles: jest.fn().mockResolvedValue(minted),
+  manufacturerOwner: jest.fn().mockResolvedValue(owner ? { owner, tokenId: 131 } : null),
+  curators: [CURATOR],
+});
+
+describe('resolveEntitlement', () => {
+  it('lets any signed-in account create a template that does not exist', async () => {
+    expect(
+      await resolveEntitlement({ caller: CALLER, template: null, ...deps(0, OTHER) }),
+    ).toMatchObject({
+      kind: 'create',
+      canPublish: true,
+      canSetHardwareTemplateId: false,
+    });
+  });
+
+  it('lets the author edit an unreferenced template', async () => {
+    const e = await resolveEntitlement({
+      caller: CALLER,
+      template: template({ author: CALLER }),
+      ...deps(0, OTHER),
+    });
+    expect(e).toMatchObject({ kind: 'author', canPublish: true });
+  });
+
+  it('treats an unauthored backfill template as unowned while nothing references it', async () => {
+    const e = await resolveEntitlement({
+      caller: CALLER,
+      template: template(),
+      ...deps(0, OTHER),
+    });
+    expect(e).toMatchObject({ kind: 'author', canPublish: true });
+  });
+
+  it('requires a proposal to edit somebody else unreferenced template', async () => {
+    const e = await resolveEntitlement({
+      caller: CALLER,
+      template: template({ author: OTHER }),
+      ...deps(0, OTHER),
+    });
+    expect(e).toMatchObject({ kind: 'proposal-required', canPublish: false });
+  });
+
+  it('lets the manufacturer NFT holder edit a template with minted vehicles', async () => {
+    const e = await resolveEntitlement({
+      caller: CALLER,
+      template: template({ author: OTHER }),
+      ...deps(4212, CALLER.toUpperCase()),
+    });
+    expect(e).toMatchObject({
+      kind: 'manufacturer',
+      canPublish: true,
+      mintedVehicles: 4212,
+    });
+  });
+
+  it('requires a proposal for everyone else once vehicles are minted, and says how many', async () => {
+    const e = await resolveEntitlement({
+      caller: CALLER,
+      template: template({ author: CALLER }),
+      ...deps(4212, OTHER),
+    });
+    expect(e).toMatchObject({
+      kind: 'proposal-required',
+      canPublish: false,
+      mintedVehicles: 4212,
+    });
+  });
+
+  it('gives a curator publish rights and the only hardwareTemplateId rights', async () => {
+    const e = await resolveEntitlement({
+      caller: CURATOR,
+      template: template({ author: OTHER }),
+      ...deps(4212, OTHER),
+    });
+    expect(e).toMatchObject({
+      kind: 'curator',
+      canPublish: true,
+      canSetHardwareTemplateId: true,
+    });
+  });
+
+  it('never grants hardwareTemplateId rights to a non-curator, at any tier', async () => {
+    for (const t of [null, template({ author: CALLER })]) {
+      const e = await resolveEntitlement({
+        caller: CALLER,
+        template: t,
+        ...deps(0, CALLER),
+      });
+      expect(e.canSetHardwareTemplateId).toBe(false);
+    }
+  });
+});
+```
+
+- [ ] **Step 2: Implement entitlement**
+
+Create `src/services/templateEntitlement.ts`:
+
+```ts
+import config from '@/config';
+import type { Template } from '@/types/template';
+import { getUserByToken } from '@/services/user';
+import { getUserSubOrganization } from '@/services/globalAccount';
+
+export type EntitlementKind =
+  | 'create'
+  | 'author'
+  | 'manufacturer'
+  | 'curator'
+  | 'proposal-required';
+
+export interface Entitlement {
+  kind: EntitlementKind;
+  canPublish: boolean;
+  /** DIMO only, at every tier. It decides what hardware ships. */
+  canSetHardwareTemplateId: boolean;
+  mintedVehicles: number;
+  reason: string;
+}
+
+const eq = (a?: string | null, b?: string | null) =>
+  Boolean(a && b && a.toLowerCase() === b.toLowerCase());
+
+export const curatorAddresses = (): string[] =>
+  (process.env.DIMO_CURATOR_ADDRESSES ?? '')
+    .split(',')
+    .map((a) => a.trim().toLowerCase())
+    .filter((a) => a.length > 0);
+
+/**
+ * The caller, from the session Console already has. Mirrors src/middleware.ts:
+ * the session cookie identifies a user, and the Global Account sub-organisation
+ * is what turns that user into an address. The smart contract address is used,
+ * not the Turnkey EOA: it is the address DIMO records on chain, so it is the
+ * one that can hold a Manufacturer NFT.
+ */
+export async function resolveCaller(): Promise<{
+  address: `0x${string}`;
+  email: string;
+} | null> {
+  try {
+    const user = await getUserByToken();
+    const email = user.company_email_owner ?? user.email;
+    const sub = await getUserSubOrganization(email);
+    if (!sub?.smartContractAddress) return null;
+    return { address: sub.smartContractAddress, email };
+  } catch {
+    return null;
+  }
+}
+
+async function identity<T>(
+  query: string,
+  variables: Record<string, unknown>,
+): Promise<T | null> {
+  const resp = await fetch(config.identityApiUrl, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ query, variables }),
+    cache: 'no-store',
+  });
+  if (!resp.ok) throw new Error(`identity-api returned ${resp.status}`);
+  const json = (await resp.json()) as { data?: T };
+  return json.data ?? null;
+}
+
+/** How many vehicles point at this template. This is the number that decides risk. */
+export async function countMintedVehicles(id: string): Promise<number> {
+  const data = await identity<{ vehicles: { totalCount: number } }>(
+    `query TemplateVehicles($id: String!) {
+       vehicles(filterBy: { deviceDefinitionId: $id }, first: 1) { totalCount }
+     }`,
+    { id },
+  );
+  return data?.vehicles.totalCount ?? 0;
+}
+
+export async function manufacturerOwner(
+  slug: string,
+): Promise<{ owner: string; tokenId: number } | null> {
+  const data = await identity<{
+    manufacturer: { owner: string; tokenId: number } | null;
+  }>(
+    `query TemplateManufacturer($slug: String!) {
+       manufacturer(by: { slug: $slug }) { owner tokenId }
+     }`,
+    { slug },
+  );
+  return data?.manufacturer ?? null;
+}
+
+export interface EntitlementArgs {
+  caller: string;
+  template: Template | null;
+  countMintedVehicles: (id: string) => Promise<number>;
+  manufacturerOwner: (slug: string) => Promise<{ owner: string; tokenId: number } | null>;
+  curators: string[];
+}
+
+/**
+ * The split falls where risk falls. Creating ineos_grenadier_2024 harms nobody.
+ * Editing toyota_camry_2020 silently re-describes every vehicle pointing at it.
+ */
+export async function resolveEntitlement(args: EntitlementArgs): Promise<Entitlement> {
+  const { caller, template, curators } = args;
+  const isCurator = curators.some((c) => eq(c, caller));
+
+  if (template === null) {
+    return {
+      kind: isCurator ? 'curator' : 'create',
+      canPublish: true,
+      canSetHardwareTemplateId: isCurator,
+      mintedVehicles: 0,
+      reason:
+        'This template does not exist yet, so creating it cannot re-describe anything.',
+    };
+  }
+
+  if (isCurator) {
+    return {
+      kind: 'curator',
+      canPublish: true,
+      canSetHardwareTemplateId: true,
+      mintedVehicles: await args.countMintedVehicles(template.id),
+      reason: 'You are a DIMO curator.',
+    };
+  }
+
+  const mintedVehicles = await args.countMintedVehicles(template.id);
+
+  if (mintedVehicles === 0) {
+    // An absent author is a backfill-created template, which nobody has claimed.
+    // Treating it as unowned is what keeps the open tier from being empty.
+    if (!template.author || eq(template.author, caller)) {
+      return {
+        kind: 'author',
+        canPublish: true,
+        canSetHardwareTemplateId: false,
+        mintedVehicles: 0,
+        reason: 'No vehicle references this template yet.',
+      };
+    }
+    return {
+      kind: 'proposal-required',
+      canPublish: false,
+      canSetHardwareTemplateId: false,
+      mintedVehicles: 0,
+      reason: `This template was published by ${template.author}. Editing someone else's template opens a proposal, which is not built yet.`,
+    };
+  }
+
+  const owner = await args.manufacturerOwner(template.manufacturer.slug);
+  if (owner && eq(owner.owner, caller)) {
+    return {
+      kind: 'manufacturer',
+      canPublish: true,
+      canSetHardwareTemplateId: false,
+      mintedVehicles,
+      reason: `You hold the ${template.manufacturer.name} Manufacturer NFT (token ${owner.tokenId}).`,
+    };
+  }
+
+  return {
+    kind: 'proposal-required',
+    canPublish: false,
+    canSetHardwareTemplateId: false,
+    mintedVehicles,
+    reason:
+      `${mintedVehicles.toLocaleString()} minted vehicle${mintedVehicles === 1 ? '' : 's'} resolve to this ` +
+      'template. Editing it needs a proposal a curator merges, which is not built yet.',
+  };
+}
+```
+
+- [ ] **Step 3: Run the entitlement tests**
+
+Run: `npx jest __tests__/unit/services/templateEntitlement.test.ts`
+Expected: PASS, 8 tests.
+
+- [ ] **Step 4: Write the failing route tests**
+
+Create `__tests__/unit/app/templateRoute.test.ts`:
+
+```ts
+import { GET, PUT } from '@/app/api/templates/[id]/route';
+import { NextRequest } from 'next/server';
+
+jest.mock('@/services/definitions');
+jest.mock('@/services/templateEntitlement', () => ({
+  ...jest.requireActual('@/services/templateEntitlement'),
+  resolveCaller: jest.fn(),
+  countMintedVehicles: jest.fn().mockResolvedValue(0),
+  manufacturerOwner: jest.fn().mockResolvedValue(null),
+  curatorAddresses: jest.fn().mockReturnValue([]),
+}));
+
+import { fetchTemplate, fetchVocabulary, publishTemplate } from '@/services/definitions';
+import {
+  resolveCaller,
+  countMintedVehicles,
+  curatorAddresses,
+} from '@/services/templateEntitlement';
+
+const CALLER = '0x1111111111111111111111111111111111111111';
+const params = { params: Promise.resolve({ id: 'toyota_camry_2020' }) };
+
+const body = (over: Record<string, unknown> = {}) => ({
+  id: 'toyota_camry_2020',
+  deviceType: 'vehicle',
+  manufacturer: { slug: 'toyota', name: 'Toyota' },
+  model: 'Camry',
+  year: 2020,
+  attributes: {},
+  trims: [{ name: 'LE', attributes: {} }],
+  ...over,
+});
+
+const put = (payload: unknown, headers: Record<string, string> = {}) =>
+  new NextRequest('https://console.test/api/templates/toyota_camry_2020', {
+    method: 'PUT',
+    headers: { 'content-type': 'application/json', ...headers },
+    body: JSON.stringify(payload),
+  });
+
+const stored = { ...body(), version: 3, author: CALLER, createdAt: 'x', updatedAt: 'y' };
+
+describe('PUT /api/templates/[id]', () => {
+  beforeEach(() => {
+    (resolveCaller as jest.Mock).mockResolvedValue({ address: CALLER, email: 'a@b.c' });
+    (fetchTemplate as jest.Mock).mockResolvedValue(stored);
+    (publishTemplate as jest.Mock).mockResolvedValue({
+      ok: true,
+      template: { ...stored, version: 4 },
+    });
+    (countMintedVehicles as jest.Mock).mockResolvedValue(0);
+    (curatorAddresses as jest.Mock).mockReturnValue([]);
+  });
+
+  it('401s when there is no session', async () => {
+    (resolveCaller as jest.Mock).mockResolvedValue(null);
+    expect((await PUT(put(body()), params)).status).toBe(401);
+  });
+
+  it('stamps author from the session and never from the body', async () => {
+    await PUT(put(body(), { 'if-match': '"3"' }), params);
+    expect((publishTemplate as jest.Mock).mock.calls[0][1].author).toBe(CALLER);
+  });
+
+  it('rejects a body that tries to name its own author or version, rather than stripping it quietly', async () => {
+    for (const field of ['author', 'version', 'createdAt', 'updatedAt']) {
+      const resp = await PUT(
+        put(body({ [field]: field === 'version' ? 9 : 'x' })),
+        params,
+      );
+      expect(resp.status).toBe(400);
+      expect((await resp.json()).error).toContain(field);
+    }
+  });
+
+  it('requires If-Match when the template already exists', async () => {
+    const resp = await PUT(put(body()), params);
+    expect(resp.status).toBe(428);
+  });
+
+  it('forwards the client If-Match rather than the version it just read', async () => {
+    // The freshly-read version would silently rebase a stale editor onto
+    // whatever landed while it was open. The client's own version is the only
+    // one that means "this is what I edited".
+    await PUT(put(body(), { 'if-match': '"2"' }), params);
+    expect((publishTemplate as jest.Mock).mock.calls[0][2]).toEqual({
+      kind: 'update',
+      version: 2,
+    });
+  });
+
+  it('sends If-None-Match on a create', async () => {
+    (fetchTemplate as jest.Mock).mockResolvedValue(null);
+    await PUT(put(body()), params);
+    expect((publishTemplate as jest.Mock).mock.calls[0][2]).toEqual({ kind: 'create' });
+  });
+
+  it('403s a caller who needs a proposal, and names the count', async () => {
+    (countMintedVehicles as jest.Mock).mockResolvedValue(4212);
+    const resp = await PUT(put(body(), { 'if-match': '"3"' }), params);
+    expect(resp.status).toBe(403);
+    expect((await resp.json()).entitlement).toMatchObject({
+      kind: 'proposal-required',
+      mintedVehicles: 4212,
+    });
+    expect(publishTemplate).not.toHaveBeenCalled();
+  });
+
+  it('403s a hardwareTemplateId change from a non-curator, at every tier', async () => {
+    const resp = await PUT(
+      put(body({ hardwareTemplateId: '999' }), { 'if-match': '"3"' }),
+      params,
+    );
+    expect(resp.status).toBe(403);
+    expect((await resp.json()).error).toContain('hardwareTemplateId');
+    expect(publishTemplate).not.toHaveBeenCalled();
+  });
+
+  it('lets a curator set hardwareTemplateId', async () => {
+    (curatorAddresses as jest.Mock).mockReturnValue([CALLER.toLowerCase()]);
+    const resp = await PUT(
+      put(body({ hardwareTemplateId: '999' }), { 'if-match': '"3"' }),
+      params,
+    );
+    expect(resp.status).toBe(200);
+  });
+
+  it('passes the worker validation errors through unchanged', async () => {
+    (publishTemplate as jest.Mock).mockResolvedValue({
+      ok: false,
+      kind: 'validation',
+      errors: ['template: unknown attribute "nope"'],
+    });
+    const resp = await PUT(put(body(), { 'if-match': '"3"' }), params);
+    expect(resp.status).toBe(422);
+    expect((await resp.json()).errors).toEqual(['template: unknown attribute "nope"']);
+  });
+
+  it('turns a worker 412 into a 409 carrying the version to rebase onto', async () => {
+    (publishTemplate as jest.Mock).mockResolvedValue({
+      ok: false,
+      kind: 'conflict',
+      expected: 3,
+      actual: 5,
+    });
+    const resp = await PUT(put(body(), { 'if-match': '"3"' }), params);
+    expect(resp.status).toBe(409);
+    expect(await resp.json()).toMatchObject({ conflict: { expected: 3, actual: 5 } });
+  });
+});
+
+describe('GET /api/templates/[id]', () => {
+  it('returns the template, the live vocabulary and the caller entitlement in one payload', async () => {
+    (resolveCaller as jest.Mock).mockResolvedValue({ address: CALLER, email: 'a@b.c' });
+    (fetchTemplate as jest.Mock).mockResolvedValue(stored);
+    (fetchVocabulary as jest.Mock).mockResolvedValue({
+      id: 'vehicle',
+      name: 'Vehicle',
+      attributes: [],
+    });
+    const json = await (
+      await GET(
+        new NextRequest('https://console.test/api/templates/toyota_camry_2020'),
+        params,
+      )
+    ).json();
+    expect(json.template.version).toBe(3);
+    expect(json.vocabulary.id).toBe('vehicle');
+    expect(json.entitlement.kind).toBe('author');
+  });
+});
+```
+
+- [ ] **Step 5: Implement the route**
+
+Create `src/app/api/templates/[id]/route.ts`:
+
+```ts
+import { NextRequest, NextResponse } from 'next/server';
+import * as Sentry from '@sentry/nextjs';
+import {
+  fetchTemplate,
+  fetchVocabulary,
+  publishTemplate,
+  type Precondition,
+} from '@/services/definitions';
+import {
+  countMintedVehicles,
+  curatorAddresses,
+  manufacturerOwner,
+  resolveCaller,
+  resolveEntitlement,
+} from '@/services/templateEntitlement';
+import type { TemplatePayload } from '@/types/template';
+
+// Server-owned. definitions-worker rejects them as unexpected top-level keys,
+// and `author` is stamped below from the session. A body carrying any of them
+// is refused by name rather than silently stripped: a client that thinks it set
+// the author and was quietly overruled has learned nothing.
+const SERVER_OWNED = ['version', 'createdAt', 'updatedAt', 'author'] as const;
+
+type Params = { params: Promise<{ id: string }> };
+
+async function entitlementFor(caller: string, id: string) {
+  const template = await fetchTemplate(id);
+  const entitlement = await resolveEntitlement({
+    caller,
+    template,
+    countMintedVehicles,
+    manufacturerOwner,
+    curators: curatorAddresses(),
+  });
+  return { template, entitlement };
+}
+
+export async function GET(_req: NextRequest, { params }: Params) {
+  const { id } = await params;
+  const caller = await resolveCaller();
+  if (!caller) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+
+  try {
+    const [{ template, entitlement }, vocabulary] = await Promise.all([
+      entitlementFor(caller.address, id),
+      fetchVocabulary(),
+    ]);
+    return NextResponse.json({ template, vocabulary, entitlement });
+  } catch (err) {
+    Sentry.captureException(err);
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : 'Failed to load template' },
+      { status: 502 },
+    );
+  }
+}
+
+export async function PUT(req: NextRequest, { params }: Params) {
+  const { id } = await params;
+  const caller = await resolveCaller();
+  if (!caller) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+
+  let submitted: Record<string, unknown>;
+  try {
+    submitted = (await req.json()) as Record<string, unknown>;
+  } catch {
+    return NextResponse.json({ error: 'body is not valid JSON' }, { status: 400 });
+  }
+
+  for (const field of SERVER_OWNED) {
+    if (field in submitted) {
+      return NextResponse.json(
+        {
+          error: `${field} is set by the server, not by the client — remove it from the body`,
+        },
+        { status: 400 },
+      );
+    }
+  }
+  if (submitted.id !== id) {
+    return NextResponse.json(
+      { error: `body id does not match path id "${id}"` },
+      { status: 400 },
+    );
+  }
+
+  try {
+    const { template, entitlement } = await entitlementFor(caller.address, id);
+
+    if (!entitlement.canPublish) {
+      return NextResponse.json(
+        { error: entitlement.reason, entitlement },
+        { status: 403 },
+      );
+    }
+
+    // hardwareTemplateId decides what hardware ships. It is not a vehicle
+    // attribute and it is never open, at any tier.
+    const submittedHw = submitted.hardwareTemplateId as string | undefined;
+    if (
+      submittedHw !== template?.hardwareTemplateId &&
+      !entitlement.canSetHardwareTemplateId
+    ) {
+      return NextResponse.json(
+        {
+          error:
+            'hardwareTemplateId is set by DIMO only — it decides what hardware ships, and is not a vehicle attribute',
+          entitlement,
+        },
+        { status: 403 },
+      );
+    }
+
+    // The precondition comes from the CLIENT, never from the template we just
+    // read. Using the fresh version would rebase a stale editor onto whatever
+    // landed while it was open -- a lost update with a 200 on it, which is the
+    // exact failure the worker's CAS exists to make impossible.
+    let precondition: Precondition;
+    if (template === null) {
+      precondition = { kind: 'create' };
+    } else {
+      const ifMatch = req.headers.get('if-match');
+      const version = Number((ifMatch ?? '').replace(/^W\//, '').replace(/"/g, ''));
+      if (!Number.isInteger(version) || version < 1) {
+        return NextResponse.json(
+          {
+            error:
+              'If-Match is required when editing an existing template: send the version you loaded',
+          },
+          { status: 428 },
+        );
+      }
+      precondition = { kind: 'update', version };
+    }
+
+    // TemplatePayload deliberately excludes `author` -- it is not client input.
+    // The wire body does carry it, stamped here, which is the one place the two
+    // shapes differ.
+    const payload = {
+      ...submitted,
+      author: caller.address,
+    } as unknown as TemplatePayload;
+    const result = await publishTemplate(id, payload, precondition);
+
+    if (result.ok) return NextResponse.json({ template: result.template });
+    if (result.kind === 'validation')
+      return NextResponse.json({ errors: result.errors }, { status: 422 });
+    if (result.kind === 'conflict') {
+      return NextResponse.json(
+        {
+          error: 'This template changed while you were editing it.',
+          conflict: { expected: result.expected, actual: result.actual },
+        },
+        { status: 409 },
+      );
+    }
+    if (result.kind === 'too-large') {
+      return NextResponse.json(
+        {
+          error: `This template is ${result.bytes} bytes; the limit is ${result.limit}.`,
+        },
+        { status: 413 },
+      );
+    }
+    Sentry.captureMessage(`definitions-worker ${result.status}: ${result.message}`);
+    return NextResponse.json({ error: result.message }, { status: 502 });
+  } catch (err) {
+    Sentry.captureException(err);
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : 'Failed to publish template' },
+      { status: 502 },
+    );
+  }
+}
+```
+
+- [ ] **Step 6: Run the route tests**
+
+Run: `npx jest __tests__/unit/app/templateRoute.test.ts && npm run compile`
+Expected: PASS, 12 tests; typecheck clean.
+
+- [ ] **Step 7: Verify the token cannot reach the browser**
+
+Run:
+
+```bash
+grep -rn "DEFINITIONS_WRITE_TOKEN" src/ | grep -v "src/services/definitions.ts"
+```
+
+Expected: no output. The only reference is inside the server-only module, which
+throws if it is ever evaluated in a browser.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add src/services/templateEntitlement.ts src/app/api/templates/[id]/route.ts \
+  __tests__/unit/services/templateEntitlement.test.ts __tests__/unit/app/templateRoute.test.ts
+git commit -m "feat(templates): per-caller authorization for template writes
+
+The worker has one shared WRITE_TOKEN and takes author on trust. This route
+holds the token server-side, identifies the caller from the session Console
+already has, stamps author from it, and refuses a body that tries to name its
+own author or version rather than stripping it quietly.
+
+Entitlement follows risk: creating a template harms nobody, editing one that
+4,212 vehicles resolve to re-describes all of them. hardwareTemplateId is
+curator-only at every tier. The If-Match forwarded is the client's, never the
+version this route just read -- the latter would rebase a stale editor onto
+whatever landed while it was open and return 200."
+```
+
+---
+
+### Task 10: The three honesty surfaces
+
+Section 8 of the handoff names the failure mode this project keeps producing:
+_correct behaviour that leaves no trace._ These three components are where the
+editor leaves a trace — what it changed that you did not type, what it will
+refuse, and what you are not allowed to do.
+
+**Files:**
+
+- Create: `src/components/TemplateEditor/NormalisationPanel/NormalisationPanel.tsx`, `index.ts`
+- Create: `src/components/TemplateEditor/TrimSelectorEditor/TrimSelectorEditor.tsx`, `index.ts`
+- Create: `src/components/TemplateEditor/EntitlementBanner/EntitlementBanner.tsx`, `index.ts`
+- Test: `src/components/TemplateEditor/__tests__/honestySurfaces.test.tsx`
+
+**Interfaces:**
+
+- Consumes: `Normalisation` from `@/utils/templateCoerce`; `hasEffectiveSelector`, `renameTrim`, `removeTrim`, `setSelectors` from `@/utils/templateGrid`; `Entitlement` from `@/services/templateEntitlement`.
+- Produces:
+  - `<NormalisationPanel notes={Normalisation[]} onDismiss={() => void} />`
+  - `<TrimSelectorEditor template trimIndex readOnly? onChange />`
+  - `<EntitlementBanner entitlement={Entitlement} />`
+
+- [ ] **Step 1: Write the failing tests**
+
+Create `src/components/TemplateEditor/__tests__/honestySurfaces.test.tsx`:
+
+```tsx
+import { render, screen, fireEvent } from '@testing-library/react';
+import camry from '@/utils/__tests__/fixtures/toyota_camry_2020.json';
+import { NormalisationPanel } from '@/components/TemplateEditor/NormalisationPanel';
+import { TrimSelectorEditor } from '@/components/TemplateEditor/TrimSelectorEditor';
+import { EntitlementBanner } from '@/components/TemplateEditor/EntitlementBanner';
+import type { Template } from '@/types/template';
+
+const t = camry as unknown as Template;
+
+describe('NormalisationPanel', () => {
+  it('renders nothing when the editor changed nothing', () => {
+    const { container } = render(<NormalisationPanel notes={[]} onDismiss={() => {}} />);
+    expect(container).toBeEmptyDOMElement();
+  });
+
+  it('says what was stored instead of what was typed', () => {
+    render(
+      <NormalisationPanel
+        notes={[
+          {
+            attribute: 'fuel_tank_capacity_gal',
+            from: '15.800000',
+            to: 15.8,
+            reason: 'stored as the number 15.8, not the text "15.800000"',
+          },
+          {
+            attribute: 'mpg_city',
+            from: '',
+            to: null,
+            reason: 'cleared — the attribute is removed, not stored empty',
+          },
+        ]}
+        onDismiss={() => {}}
+      />,
+    );
+    expect(screen.getByText(/stored as the number 15.8/)).toBeInTheDocument();
+    expect(
+      screen.getByText(/the attribute is removed, not stored empty/),
+    ).toBeInTheDocument();
+  });
+});
+
+describe('TrimSelectorEditor', () => {
+  it('shows the gate 4 state for a trim with no effective selector', () => {
+    const broken = {
+      ...t,
+      trims: [
+        ...t.trims,
+        { name: 'XLE V6', attributes: {}, selectors: { vinPattern: '  ' } },
+      ],
+    } as Template;
+    render(
+      <TrimSelectorEditor
+        template={broken}
+        trimIndex={broken.trims.length - 1}
+        onChange={() => {}}
+      />,
+    );
+    expect(screen.getByRole('alert')).toHaveTextContent(
+      'A template with more than one trim cannot have a selector-less trim',
+    );
+  });
+
+  it('is quiet when the trim has a real selector', () => {
+    render(<TrimSelectorEditor template={t} trimIndex={0} onChange={() => {}} />);
+    expect(screen.queryByRole('alert')).toBeNull();
+  });
+
+  it('splits a comma separated list into manufacturer codes and drops the blanks', () => {
+    const onChange = jest.fn();
+    render(<TrimSelectorEditor template={t} trimIndex={0} onChange={onChange} />);
+    fireEvent.change(screen.getByLabelText(/manufacturer code/i), {
+      target: { value: '2532, , 2533 ' },
+    });
+    expect(onChange.mock.calls.at(-1)![0].trims[0].selectors.manufacturerCode).toEqual([
+      '2532',
+      '2533',
+    ]);
+  });
+});
+
+describe('EntitlementBanner', () => {
+  it('explains a proposal requirement and names the vehicle count', () => {
+    render(
+      <EntitlementBanner
+        entitlement={{
+          kind: 'proposal-required',
+          canPublish: false,
+          canSetHardwareTemplateId: false,
+          mintedVehicles: 4212,
+          reason: '4,212 minted vehicles resolve to this template.',
+        }}
+      />,
+    );
+    expect(screen.getByRole('status')).toHaveTextContent(
+      '4,212 minted vehicles resolve to this template.',
+    );
+    expect(screen.getByRole('status')).toHaveTextContent('read only');
+  });
+
+  it('says nothing loud when the caller may publish', () => {
+    render(
+      <EntitlementBanner
+        entitlement={{
+          kind: 'author',
+          canPublish: true,
+          canSetHardwareTemplateId: false,
+          mintedVehicles: 0,
+          reason: 'No vehicle references this template yet.',
+        }}
+      />,
+    );
+    expect(screen.getByRole('status')).toHaveTextContent(
+      'No vehicle references this template yet.',
+    );
+    expect(screen.getByRole('status').className).not.toContain('red');
+  });
+});
+```
+
+- [ ] **Step 2: Run and watch it fail**
+
+Run: `npx jest src/components/TemplateEditor/__tests__/honestySurfaces.test.tsx`
+Expected: FAIL — modules not found.
+
+- [ ] **Step 3: Implement `NormalisationPanel`**
+
+Create `src/components/TemplateEditor/NormalisationPanel/NormalisationPanel.tsx`:
+
+```tsx
+import React, { type FC } from 'react';
+import type { Normalisation } from '@/utils/templateCoerce';
+
+interface Props {
+  notes: Normalisation[];
+  onDismiss: () => void;
+}
+
+/**
+ * Everything the editor stored that is not literally what was typed. A value
+ * that changes without a report is the failure mode this project keeps
+ * producing; this is where it is refused. Absent when there is nothing to say.
+ */
+export const NormalisationPanel: FC<Props> = ({ notes, onDismiss }) => {
+  if (notes.length === 0) return null;
+  return (
+    <section className="rounded-xl border border-cta-default bg-surface-raised p-4">
+      <div className="flex items-start justify-between gap-4">
+        <h2 className="text-white">What the editor changed that you did not type</h2>
+        <button
+          type="button"
+          onClick={onDismiss}
+          className="text-xs text-white/50 hover:text-white"
+        >
+          Dismiss
+        </button>
+      </div>
+      <ul className="flex flex-col gap-1 pt-2">
+        {notes.map((n, i) => (
+          <li key={`${n.attribute}-${i}`} className="text-white/70">
+            <span className="font-mono text-white/50">{n.attribute}</span>
+            <span className="px-2 text-white/25">·</span>
+            {n.reason}
+          </li>
+        ))}
+      </ul>
+    </section>
+  );
+};
+```
+
+`index.ts`: `export * from './NormalisationPanel';`
+
+- [ ] **Step 4: Implement `TrimSelectorEditor`**
+
+Create `src/components/TemplateEditor/TrimSelectorEditor/TrimSelectorEditor.tsx`:
+
+```tsx
+import React, { type FC } from 'react';
+import type { Template, TrimSelectors } from '@/types/template';
+import {
+  hasEffectiveSelector,
+  removeTrim,
+  renameTrim,
+  setSelectors,
+} from '@/utils/templateGrid';
+
+interface Props {
+  template: Template;
+  trimIndex: number;
+  readOnly?: boolean;
+  onChange: (next: Template) => void;
+}
+
+const toList = (raw: string) =>
+  raw
+    .split(',')
+    .map((s) => s.trim())
+    .filter((s) => s.length > 0);
+const fromList = (values?: string[]) => (values ?? []).join(', ');
+
+export const TrimSelectorEditor: FC<Props> = ({
+  template,
+  trimIndex,
+  readOnly,
+  onChange,
+}) => {
+  const trim = template.trims[trimIndex];
+  const multiTrim = template.trims.length > 1;
+  const missing = multiTrim && !hasEffectiveSelector(trim.selectors);
+
+  const update = (patch: Partial<TrimSelectors>) =>
+    onChange(setSelectors(template, trimIndex, { ...trim.selectors, ...patch }));
+
+  const field = (
+    label: string,
+    value: string,
+    onValue: (raw: string) => void,
+    placeholder: string,
+  ) => (
+    <label className="flex flex-col gap-1">
+      <span className="text-xs uppercase tracking-wide text-white/50">{label}</span>
+      <input
+        aria-label={label}
+        value={value}
+        readOnly={readOnly}
+        placeholder={placeholder}
+        onChange={(e) => onValue(e.target.value)}
+        className="h-10 rounded-md bg-dark-grey-950 px-3 text-white placeholder:text-white/25"
+      />
+    </label>
+  );
+
+  return (
+    <section className="flex flex-col gap-3 rounded-xl border border-cta-default bg-surface-default p-4">
+      <div className="flex items-center justify-between gap-4">
+        <input
+          aria-label="Trim name"
+          value={trim.name}
+          readOnly={readOnly}
+          onChange={(e) => onChange(renameTrim(template, trimIndex, e.target.value))}
+          className="h-10 flex-1 rounded-md bg-dark-grey-950 px-3 text-white"
+        />
+        {!readOnly && multiTrim && (
+          <button
+            type="button"
+            onClick={() => onChange(removeTrim(template, trimIndex))}
+            className="rounded-full border border-cta-default px-3 py-1 text-xs text-white/70 hover:border-white hover:text-white"
+          >
+            Remove trim
+          </button>
+        )}
+      </div>
+
+      <div className="grid gap-3 md:grid-cols-3">
+        {field(
+          'Manufacturer code',
+          fromList(trim.selectors?.manufacturerCode),
+          (raw) => update({ manufacturerCode: toList(raw) }),
+          '2532, 2546',
+        )}
+        {field(
+          'Style name',
+          fromList(trim.selectors?.styleName),
+          (raw) => update({ styleName: toList(raw) }),
+          'Hybrid LE',
+        )}
+        {field(
+          'VIN pattern',
+          trim.selectors?.vinPattern ?? '',
+          (raw) => update({ vinPattern: raw }),
+          '^4T1B11HK.*$',
+        )}
+      </div>
+
+      {missing && (
+        <p role="alert" className="text-red-400">
+          A template with more than one trim cannot have a selector-less trim: it would
+          match every signal and make every decode for this model-year ambiguous. Give
+          this trim a manufacturer code, a style name or a VIN pattern.
+        </p>
+      )}
+    </section>
+  );
+};
+```
+
+`index.ts`: `export * from './TrimSelectorEditor';`
+
+- [ ] **Step 5: Implement `EntitlementBanner`**
+
+Create `src/components/TemplateEditor/EntitlementBanner/EntitlementBanner.tsx`:
+
+```tsx
+import React, { type FC } from 'react';
+import classnames from 'classnames';
+// `import type`, not a value import: templateEntitlement reaches next/headers
+// through getUserByToken, and pulling it into a client component would break the
+// build. The type is erased; the module is never bundled.
+import type { Entitlement } from '@/services/templateEntitlement';
+
+const TITLES: Record<Entitlement['kind'], string> = {
+  'create': 'New template',
+  'author': 'You can publish this',
+  'manufacturer': 'You hold this Manufacturer NFT',
+  'curator': 'Curator',
+  'proposal-required': 'Read only',
+};
+
+export const EntitlementBanner: FC<{ entitlement: Entitlement }> = ({ entitlement }) => (
+  <div
+    role="status"
+    className={classnames(
+      'flex flex-col gap-1 rounded-xl border p-4',
+      entitlement.canPublish
+        ? 'border-cta-default bg-surface-default text-white/70'
+        : 'border-red-400/40 bg-surface-raised text-white/70',
+    )}
+  >
+    <span className={entitlement.canPublish ? 'text-white' : 'text-red-400'}>
+      {TITLES[entitlement.kind]}
+      {!entitlement.canPublish && ' — read only'}
+    </span>
+    <span>{entitlement.reason}</span>
+    {!entitlement.canSetHardwareTemplateId && (
+      <span className="text-white/40">
+        hardwareTemplateId decides what hardware ships and is set by DIMO only.
+      </span>
+    )}
+  </div>
+);
+```
+
+`index.ts`: `export * from './EntitlementBanner';`
+
+- [ ] **Step 6: Run the tests and commit**
+
+Run: `npx jest src/components/TemplateEditor && npm run compile && npm run lint`
+Expected: PASS; typecheck and lint clean.
+
+```bash
+git add src/components/TemplateEditor
+git commit -m "feat(templates): normalisation report, selector editor, entitlement banner
+
+Three places the editor leaves a trace instead of acting quietly: what it
+stored that differs from what was typed, why a selector-less trim will be
+refused before save rather than at it, and what the caller is not allowed to
+do and why."
+```
+
+---
+
+### Task 11: The editor page
+
+**Files:**
+
+- Create: `src/app/templates/[id]/page.tsx`
+- Create: `src/app/templates/[id]/components/View/View.tsx`, `index.ts`
+- Create: `src/hooks/queries/useTemplate.ts`
+- Test: `src/app/templates/[id]/__tests__/View.test.tsx`
+
+**Interfaces:**
+
+- Consumes: `GET`/`PUT /api/templates/[id]` (Task 9); `TrimGrid` (Task 7); `NormalisationPanel`, `TrimSelectorEditor`, `EntitlementBanner` (Task 10); `toPayload`, `addTrim` (Task 5); `validateDraft` (Task 6).
+- Produces: `useTemplate(id)` → `{ data, isLoading, error }`; `usePublishTemplate(id)` → TanStack mutation; the page at `/templates/<id>`.
+
+- [ ] **Step 1: The data hooks**
+
+Create `src/hooks/queries/useTemplate.ts`:
+
+```ts
+'use client';
+
+import { useMutation, useQuery } from '@tanstack/react-query';
+import type { DeviceType, Template, TemplatePayload } from '@/types/template';
+import type { Entitlement } from '@/services/templateEntitlement';
+
+export interface TemplateBundle {
+  template: Template | null;
+  vocabulary: DeviceType;
+  entitlement: Entitlement;
+}
+
+export interface PublishFailure {
+  status: number;
+  message?: string;
+  errors?: string[];
+  conflict?: { expected: number | null; actual: number };
+}
+
+export const useTemplate = (id: string) =>
+  useQuery<TemplateBundle>({
+    queryKey: ['template', id],
+    // The version held here is what If-Match sends. A cached one would send a
+    // stale precondition and turn a real conflict into a silent rebase.
+    staleTime: 0,
+    refetchOnWindowFocus: false,
+    queryFn: async () => {
+      const resp = await fetch(`/api/templates/${encodeURIComponent(id)}`);
+      const json = await resp.json();
+      if (!resp.ok) throw new Error(json.error ?? 'Failed to load template');
+      return json as TemplateBundle;
+    },
+  });
+
+export const usePublishTemplate = (id: string) =>
+  useMutation<
+    Template,
+    PublishFailure,
+    { payload: TemplatePayload; version: number | null }
+  >({
+    mutationFn: async ({ payload, version }) => {
+      const resp = await fetch(`/api/templates/${encodeURIComponent(id)}`, {
+        method: 'PUT',
+        headers: {
+          'Content-Type': 'application/json',
+          ...(version === null ? {} : { 'If-Match': `"${version}"` }),
+        },
+        body: JSON.stringify(payload),
+      });
+      const json = await resp.json();
+      if (!resp.ok) {
+        throw {
+          status: resp.status,
+          message: json.error,
+          errors: json.errors,
+          conflict: json.conflict,
+        } as PublishFailure;
+      }
+      return json.template as Template;
+    },
+  });
+```
+
+- [ ] **Step 2: Write the failing page tests**
+
+Create `src/app/templates/[id]/__tests__/View.test.tsx`:
+
+```tsx
+import { render, screen, fireEvent, waitFor, within } from '@testing-library/react';
+import camry from '@/utils/__tests__/fixtures/toyota_camry_2020.json';
+import { vehicleVocab } from '@/utils/__tests__/fixtures/vehicleVocab';
+import { TemplateEditorView } from '../components/View';
+import type { Template } from '@/types/template';
+
+const t = camry as unknown as Template;
+
+const publish = jest.fn();
+const refetch = jest.fn();
+
+// A mutable bundle rather than a second module mock: the read-only branch is a
+// different entitlement, not a different module, and the component must derive
+// it from the data it is given.
+let bundle: {
+  template: Template;
+  vocabulary: typeof vehicleVocab;
+  entitlement: {
+    kind: string;
+    canPublish: boolean;
+    canSetHardwareTemplateId: boolean;
+    mintedVehicles: number;
+    reason: string;
+  };
+};
+
+jest.mock('@/hooks/queries/useTemplate', () => ({
+  useTemplate: () => ({ data: bundle, isLoading: false, error: null, refetch }),
+  usePublishTemplate: () => ({ mutateAsync: publish, isPending: false }),
+}));
+
+const authorBundle = () => ({
+  template: t,
+  vocabulary: vehicleVocab,
+  entitlement: {
+    kind: 'author',
+    canPublish: true,
+    canSetHardwareTemplateId: false,
+    mintedVehicles: 0,
+    reason: 'No vehicle references this template yet.',
+  },
+});
+
+/** Publish is disabled until the draft differs from what was loaded. */
+const edit = () => {
+  const input = within(screen.getByTestId('cell-mpg_city-0')).getByRole('textbox');
+  fireEvent.change(input, { target: { value: '27' } });
+  fireEvent.blur(input);
+};
+
+describe('TemplateEditorView', () => {
+  beforeEach(() => {
+    bundle = authorBundle();
+    publish.mockReset().mockResolvedValue({ ...t, version: t.version + 1 });
+    refetch.mockReset();
+  });
+
+  it('shows the current version and the author of the version it loaded', () => {
+    render(<TemplateEditorView id={t.id} />);
+    expect(screen.getByText(new RegExp(`v${t.version}`))).toBeInTheDocument();
+  });
+
+  it('leaves publish disabled until something actually changed', () => {
+    render(<TemplateEditorView id={t.id} />);
+    expect(screen.getByRole('button', { name: /^publish/i })).toBeDisabled();
+    edit();
+    expect(screen.getByRole('button', { name: /^publish/i })).toBeEnabled();
+  });
+
+  it('refuses to publish while the draft would fail the worker, and names the fault', async () => {
+    render(<TemplateEditorView id={t.id} />);
+    fireEvent.click(screen.getByRole('button', { name: /add trim/i }));
+    expect(await screen.findByText(/selectors are required/)).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /^publish/i })).toBeDisabled();
+    expect(publish).not.toHaveBeenCalled();
+  });
+
+  it('sends the version it loaded as the precondition, and never the payload server fields', async () => {
+    render(<TemplateEditorView id={t.id} />);
+    edit();
+    fireEvent.click(screen.getByRole('button', { name: /^publish/i }));
+    await waitFor(() => expect(publish).toHaveBeenCalled());
+    const { payload, version } = publish.mock.calls[0][0];
+    expect(version).toBe(t.version);
+    expect(payload.version).toBeUndefined();
+    expect(payload.author).toBeUndefined();
+    expect(payload.createdAt).toBeUndefined();
+  });
+
+  it('surfaces the worker validation errors verbatim', async () => {
+    publish.mockRejectedValue({
+      status: 422,
+      errors: ['trim LE: "mpg_city" above maximum 200'],
+    });
+    render(<TemplateEditorView id={t.id} />);
+    edit();
+    fireEvent.click(screen.getByRole('button', { name: /^publish/i }));
+    expect(
+      await screen.findByText('trim LE: "mpg_city" above maximum 200'),
+    ).toBeInTheDocument();
+  });
+
+  it('explains a conflict instead of retrying over the top of it', async () => {
+    publish.mockRejectedValue({ status: 409, conflict: { expected: 10, actual: 12 } });
+    render(<TemplateEditorView id={t.id} />);
+    edit();
+    fireEvent.click(screen.getByRole('button', { name: /^publish/i }));
+    expect(await screen.findByRole('alert')).toHaveTextContent('version 12');
+    expect(screen.getByRole('button', { name: /reload/i })).toBeInTheDocument();
+    expect(publish).toHaveBeenCalledTimes(1);
+  });
+
+  it('reports the normalisation when a typed value is not what gets stored', () => {
+    render(<TemplateEditorView id={t.id} />);
+    const input = within(screen.getByTestId('cell-fuel_tank_capacity_gal-0')).getByRole(
+      'textbox',
+    );
+    fireEvent.change(input, { target: { value: '16.000000' } });
+    fireEvent.blur(input);
+    expect(
+      screen.getByText(/What the editor changed that you did not type/),
+    ).toBeInTheDocument();
+    expect(screen.getByText(/stored as the number 16/)).toBeInTheDocument();
+  });
+
+  it('is read only, with no publish button, when a proposal is required', () => {
+    bundle = {
+      ...authorBundle(),
+      entitlement: {
+        kind: 'proposal-required',
+        canPublish: false,
+        canSetHardwareTemplateId: false,
+        mintedVehicles: 4212,
+        reason: '4,212 minted vehicles resolve to this template.',
+      },
+    };
+    render(<TemplateEditorView id={t.id} />);
+    expect(screen.queryByRole('button', { name: /^publish/i })).toBeNull();
+    expect(screen.queryAllByRole('textbox')).toHaveLength(0);
+  });
+});
+```
+
+- [ ] **Step 3: Implement the view**
+
+Create `src/app/templates/[id]/components/View/View.tsx`:
+
+```tsx
+'use client';
+
+import React, { useEffect, useMemo, useState, type FC } from 'react';
+import { Button } from '@/components/Button';
+import { QueryPageWrapper } from '@/components/QueryPageWrapper';
+import { TrimGrid } from '@/components/TemplateEditor/TrimGrid';
+import { TrimSelectorEditor } from '@/components/TemplateEditor/TrimSelectorEditor';
+import { NormalisationPanel } from '@/components/TemplateEditor/NormalisationPanel';
+import { EntitlementBanner } from '@/components/TemplateEditor/EntitlementBanner';
+import {
+  useTemplate,
+  usePublishTemplate,
+  type PublishFailure,
+} from '@/hooks/queries/useTemplate';
+import { addTrim, toPayload } from '@/utils/templateGrid';
+import { validateDraft } from '@/utils/templateValidate';
+import type { Normalisation } from '@/utils/templateCoerce';
+import type { Template } from '@/types/template';
+
+interface Props {
+  id: string;
+}
+
+export const TemplateEditorView: FC<Props> = ({ id }) => {
+  const { data, isLoading, error, refetch } = useTemplate(id);
+  const publish = usePublishTemplate(id);
+
+  const [draft, setDraft] = useState<Template | null>(null);
+  const [notes, setNotes] = useState<Normalisation[]>([]);
+  const [serverErrors, setServerErrors] = useState<string[]>([]);
+  const [conflict, setConflict] = useState<{
+    expected: number | null;
+    actual: number;
+  } | null>(null);
+  const [published, setPublished] = useState<number | null>(null);
+
+  // The version loaded, held apart from the draft: it is what If-Match sends,
+  // and it must not move when the draft does.
+  const loadedVersion = data?.template?.version ?? null;
+  const readOnly = !(data?.entitlement.canPublish ?? false);
+
+  useEffect(() => {
+    if (data?.template && draft === null) setDraft(data.template);
+  }, [data, draft]);
+
+  const dirty =
+    draft !== null &&
+    data?.template !== null &&
+    JSON.stringify(draft) !== JSON.stringify(data?.template);
+
+  useEffect(() => {
+    if (!dirty) return undefined;
+    const warn = (e: BeforeUnloadEvent) => {
+      e.preventDefault();
+    };
+    window.addEventListener('beforeunload', warn);
+    return () => window.removeEventListener('beforeunload', warn);
+  }, [dirty]);
+
+  const localErrors = useMemo(
+    () => (draft && data ? validateDraft(draft, data.vocabulary) : []),
+    [draft, data],
+  );
+
+  const onPublish = async () => {
+    if (!draft || loadedVersion === null) return;
+    setServerErrors([]);
+    setConflict(null);
+    try {
+      const result = await publish.mutateAsync({
+        payload: toPayload(draft),
+        version: loadedVersion,
+      });
+      setPublished(result.version);
+      setNotes([]);
+      await refetch();
+      setDraft(null);
+    } catch (err) {
+      const failure = err as PublishFailure;
+      if (failure.status === 409 && failure.conflict) setConflict(failure.conflict);
+      else setServerErrors(failure.errors ?? [failure.message ?? 'Publish failed']);
+    }
+  };
+
+  return (
+    <QueryPageWrapper
+      loading={isLoading}
+      error={error ?? undefined}
+      customErrorMessage="Could not load this template"
+    >
+      {draft && data && (
+        <div className="flex flex-col gap-6">
+          <header className="flex flex-wrap items-center justify-between gap-3">
+            <div className="flex flex-col">
+              <h1 className="text-white">
+                {draft.manufacturer.name} {draft.model} {draft.year}
+              </h1>
+              <span className="font-mono text-xs text-white/50">
+                {draft.id} · v{loadedVersion}
+                {data.template?.author && ` · last published by ${data.template.author}`}
+              </span>
+            </div>
+            {!readOnly && (
+              <div className="flex items-center gap-2">
+                <Button className="dark" onClick={() => setDraft(addTrim(draft, ''))}>
+                  Add trim
+                </Button>
+                <Button
+                  onClick={onPublish}
+                  loading={publish.isPending}
+                  disabled={localErrors.length > 0 || !dirty}
+                >
+                  Publish
+                </Button>
+              </div>
+            )}
+          </header>
+
+          <EntitlementBanner entitlement={data.entitlement} />
+
+          {published !== null && (
+            <p className="text-primary-300">Published version {published}.</p>
+          )}
+
+          {conflict && (
+            <div
+              role="alert"
+              className="flex flex-col gap-2 rounded-xl border border-red-400/40 bg-surface-raised p-4"
+            >
+              <span className="text-red-400">
+                This template moved to version {conflict.actual} while you were editing
+                version {conflict.expected}.
+              </span>
+              <span className="text-white/70">
+                Your draft has not been discarded and nothing was published. Reload to see
+                the current version, then re-apply your changes.
+              </span>
+              <div>
+                <Button
+                  className="dark"
+                  onClick={() => {
+                    setDraft(null);
+                    setConflict(null);
+                    refetch();
+                  }}
+                >
+                  Reload
+                </Button>
+              </div>
+            </div>
+          )}
+
+          {(localErrors.length > 0 || serverErrors.length > 0) && (
+            <ul className="flex flex-col gap-1 rounded-xl border border-red-400/40 bg-surface-raised p-4">
+              {[...serverErrors, ...localErrors].map((e) => (
+                <li key={e} className="text-red-400">
+                  {e}
+                </li>
+              ))}
+            </ul>
+          )}
+
+          <NormalisationPanel notes={notes} onDismiss={() => setNotes([])} />
+
+          <TrimGrid
+            template={draft}
+            vocab={data.vocabulary}
+            readOnly={readOnly}
+            onChange={setDraft}
+            onNormalise={(note) => setNotes((prev) => [...prev, note])}
+          />
+
+          <div className="flex flex-col gap-3">
+            {draft.trims.map((trim, i) => (
+              <TrimSelectorEditor
+                key={`${trim.name}-${i}`}
+                template={draft}
+                trimIndex={i}
+                readOnly={readOnly}
+                onChange={setDraft}
+              />
+            ))}
+          </div>
+        </div>
+      )}
+    </QueryPageWrapper>
+  );
+};
+```
+
+`index.ts`: `export * from './View';`
+
+Create `src/app/templates/[id]/page.tsx`:
+
+```tsx
+'use client';
+
+import React, { Suspense, use, type FC } from 'react';
+
+import { TemplateEditorView } from './components/View';
+
+const TemplatePage: FC<{ params: Promise<{ id: string }> }> = ({ params }) => {
+  const { id } = use(params);
+  return (
+    <Suspense fallback={<div>Loading...</div>}>
+      <TemplateEditorView id={decodeURIComponent(id)} />
+    </Suspense>
+  );
+};
+
+export default TemplatePage;
+```
+
+- [ ] **Step 4: Run the tests**
+
+Run: `npx jest src/app/templates && npm run compile && npm run lint`
+Expected: PASS, 8 tests; typecheck and lint clean.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add src/app/templates/\[id\] src/hooks/queries/useTemplate.ts
+git commit -m "feat(templates): the editor page
+
+Publish is disabled while the draft would fail the worker, and the fault is
+named in the worker's own words. The precondition is the version that was
+loaded, held apart from the draft so it cannot move underneath it. A conflict
+explains what happened and offers a reload -- it never retries over the top of
+somebody else's version."
+```
+
+---
+
+### Task 12: Creating a template that does not exist
+
+Creating `ineos_grenadier_2024` harms nobody, so it publishes immediately and
+attributed. The whole tier exists because the risk is not symmetrical.
+
+**Files:**
+
+- Create: `src/app/templates/new/page.tsx`
+- Create: `src/app/templates/new/components/View/View.tsx`, `index.ts`
+- Test: `src/app/templates/new/__tests__/View.test.tsx`
+
+**Interfaces:**
+
+- Consumes: `usePublishTemplate` (Task 11); `validateDraft` (Task 6); `toPayload`, `addTrim` (Task 5); `GET /api/templates?make=` (Task 8) for the manufacturer name and token id.
+- Produces: the page at `/templates/new`, and a link to it from the browse page's empty state.
+
+- [ ] **Step 1: Write the failing tests**
+
+Create `src/app/templates/new/__tests__/View.test.tsx`:
+
+```tsx
+import { render, screen, fireEvent, waitFor } from '@testing-library/react';
+import { NewTemplateView } from '../components/View';
+
+const publish = jest.fn();
+jest.mock('@/hooks/queries/useTemplate', () => ({
+  usePublishTemplate: () => ({ mutateAsync: publish, isPending: false }),
+}));
+
+const fill = (label: RegExp, value: string) =>
+  fireEvent.change(screen.getByLabelText(label), { target: { value } });
+
+describe('NewTemplateView', () => {
+  beforeEach(() =>
+    publish.mockReset().mockResolvedValue({ id: 'ineos_grenadier_2024', version: 1 }),
+  );
+
+  it('builds the id from make slug, model slug and year, and shows it', () => {
+    render(<NewTemplateView />);
+    fill(/make slug/i, 'ineos');
+    fill(/model slug/i, 'grenadier');
+    fill(/year/i, '2024');
+    expect(screen.getByTestId('derived-id')).toHaveTextContent('ineos_grenadier_2024');
+  });
+
+  it('refuses a slug the id pattern cannot accept, before any request', async () => {
+    render(<NewTemplateView />);
+    fill(/make slug/i, 'Subaru');
+    fill(/model slug/i, 'tribeca-(ny/nj)');
+    fill(/year/i, '2008');
+    fireEvent.click(screen.getByRole('button', { name: /create/i }));
+    expect(
+      await screen.findByText('id must be <make>_<model>_<year>'),
+    ).toBeInTheDocument();
+    expect(publish).not.toHaveBeenCalled();
+  });
+
+  it('creates with a null precondition so the route sends If-None-Match', async () => {
+    render(<NewTemplateView />);
+    fill(/make slug/i, 'ineos');
+    fill(/model slug/i, 'grenadier');
+    fill(/year/i, '2024');
+    fill(/manufacturer name/i, 'INEOS');
+    fill(/model name/i, 'Grenadier');
+    fill(/first trim/i, 'Trialmaster');
+    fireEvent.click(screen.getByRole('button', { name: /create/i }));
+    await waitFor(() => expect(publish).toHaveBeenCalled());
+    expect(publish.mock.calls[0][0].version).toBeNull();
+    expect(publish.mock.calls[0][0].payload.trims).toEqual([
+      { name: 'Trialmaster', attributes: {} },
+    ]);
+  });
+
+  it('says the template already exists rather than reporting a generic failure', async () => {
+    publish.mockRejectedValue({ status: 409, conflict: { expected: null, actual: 4 } });
+    render(<NewTemplateView />);
+    fill(/make slug/i, 'toyota');
+    fill(/model slug/i, 'camry');
+    fill(/year/i, '2020');
+    fill(/manufacturer name/i, 'Toyota');
+    fill(/model name/i, 'Camry');
+    fill(/first trim/i, 'LE');
+    fireEvent.click(screen.getByRole('button', { name: /create/i }));
+    expect(await screen.findByRole('alert')).toHaveTextContent('already exists');
+    expect(screen.getByRole('link', { name: /open it/i })).toHaveAttribute(
+      'href',
+      '/templates/toyota_camry_2020',
+    );
+  });
+});
+```
+
+- [ ] **Step 2: Run and watch it fail**
+
+Run: `npx jest src/app/templates/new`
+Expected: FAIL — module not found.
+
+- [ ] **Step 3: Implement the view**
+
+Create `src/app/templates/new/components/View/View.tsx`:
+
+```tsx
+'use client';
+
+import React, { useMemo, useState, type FC } from 'react';
+import Link from 'next/link';
+import { useRouter } from 'next/navigation';
+import { Button } from '@/components/Button';
+import { usePublishTemplate, type PublishFailure } from '@/hooks/queries/useTemplate';
+import { validateDraft } from '@/utils/templateValidate';
+import { toPayload } from '@/utils/templateGrid';
+import type { DeviceType, Template } from '@/types/template';
+
+// The editor's own vocabulary comes from the worker; a create form needs none
+// of it, because a new template starts with no attributes at all -- 5,152 of
+// the emitted set are attribute-free and that is a real, valid template.
+const EMPTY_VOCAB: DeviceType = { id: 'vehicle', name: 'Vehicle', attributes: [] };
+
+/** `presetId` comes from the browse page's Create link, e.g. toyota_supra_2020. */
+export const NewTemplateView: FC<{ presetId?: string }> = ({ presetId }) => {
+  const router = useRouter();
+  const [form, setForm] = useState(() => {
+    const parts = (presetId ?? '').split('_');
+    const blank = {
+      makeSlug: '',
+      modelSlug: '',
+      year: '',
+      manufacturerName: '',
+      modelName: '',
+      trimName: '',
+    };
+    return parts.length === 3
+      ? { ...blank, makeSlug: parts[0], modelSlug: parts[1], year: parts[2] }
+      : blank;
+  });
+  const [errors, setErrors] = useState<string[]>([]);
+  const [exists, setExists] = useState(false);
+
+  const id = `${form.makeSlug}_${form.modelSlug}_${form.year}`;
+  // The id is derived from the form, so the mutation has to be created after it
+  // -- usePublishTemplate('') would PUT to /api/templates/ and 404.
+  const publish = usePublishTemplate(id);
+
+  const draft = useMemo<Template>(
+    () =>
+      ({
+        id,
+        deviceType: 'vehicle',
+        manufacturer: { slug: form.makeSlug, name: form.manufacturerName },
+        model: form.modelName,
+        year: Number(form.year),
+        attributes: {},
+        trims: [{ name: form.trimName, attributes: {} }],
+      }) as Template,
+    [id, form],
+  );
+
+  const field = (key: keyof typeof form, label: string, placeholder: string) => (
+    <label key={key} className="flex flex-col gap-1">
+      <span className="text-xs uppercase tracking-wide text-white/50">{label}</span>
+      <input
+        aria-label={label}
+        value={form[key]}
+        placeholder={placeholder}
+        onChange={(e) => setForm({ ...form, [key]: e.target.value })}
+        className="h-10 rounded-md bg-dark-grey-950 px-3 text-white placeholder:text-white/25"
+      />
+    </label>
+  );
+
+  const onCreate = async () => {
+    setExists(false);
+    const found = validateDraft(draft, EMPTY_VOCAB);
+    if (found.length > 0) {
+      setErrors(found);
+      return;
+    }
+    setErrors([]);
+    try {
+      // version null -> the route sends If-None-Match: *, so a template that
+      // already exists comes back as a conflict rather than a silent overwrite.
+      await publish.mutateAsync({ payload: toPayload(draft), version: null });
+      router.push(`/templates/${id}`);
+    } catch (err) {
+      const failure = err as PublishFailure;
+      if (failure.status === 409) setExists(true);
+      else
+        setErrors(
+          failure.errors ?? [failure.message ?? 'Could not create this template'],
+        );
+    }
+  };
+
+  return (
+    <div className="flex flex-col gap-6">
+      <h1 className="text-white">New template</h1>
+      <p className="text-white/50">
+        A model-year and the trims it shipped in. Creating one publishes immediately and
+        is attributed to you — nothing points at it yet, so nothing can be re-described.
+      </p>
+
+      <div className="grid gap-3 md:grid-cols-3">
+        {field('makeSlug', 'Make slug', 'ineos')}
+        {field('modelSlug', 'Model slug', 'grenadier')}
+        {field('year', 'Year', '2024')}
+        {field('manufacturerName', 'Manufacturer name', 'INEOS')}
+        {field('modelName', 'Model name', 'Grenadier')}
+        {field('trimName', 'First trim', 'Trialmaster')}
+      </div>
+
+      <p className="font-mono text-white/70" data-testid="derived-id">
+        {id}
+      </p>
+
+      {errors.length > 0 && (
+        <ul className="flex flex-col gap-1 rounded-xl border border-red-400/40 bg-surface-raised p-4">
+          {errors.map((e) => (
+            <li key={e} className="text-red-400">
+              {e}
+            </li>
+          ))}
+        </ul>
+      )}
+
+      {exists && (
+        <div
+          role="alert"
+          className="flex items-center gap-3 rounded-xl border border-red-400/40 bg-surface-raised p-4"
+        >
+          <span className="text-red-400">A template with this id already exists.</span>
+          <Link href={`/templates/${id}`} className="button">
+            Open it
+          </Link>
+        </div>
+      )}
+
+      <div>
+        <Button onClick={onCreate} loading={publish.isPending}>
+          Create template
+        </Button>
+      </div>
+    </div>
+  );
+};
+```
+
+`index.ts`: `export * from './View';`
+
+Create `src/app/templates/new/page.tsx`:
+
+```tsx
+'use client';
+
+import React, { Suspense, type FC } from 'react';
+import { useSearchParams } from 'next/navigation';
+
+import { NewTemplateView } from './components/View';
+
+// useSearchParams must sit inside a Suspense boundary, and keeping it out of the
+// view leaves the view a pure function of its props for the tests.
+const PresetView: FC = () => {
+  const search = useSearchParams();
+  return <NewTemplateView presetId={search.get('id') ?? undefined} />;
+};
+
+const NewTemplatePage: FC = () => (
+  <Suspense fallback={<div>Loading...</div>}>
+    <PresetView />
+  </Suspense>
+);
+
+export default NewTemplatePage;
+```
+
+- [ ] **Step 4: Fix the create link on the browse page**
+
+In `src/app/templates/templatesPage/View/View.tsx`, a `missing` result links to
+`/templates/<id>`, which loads an editor for a template that does not exist.
+Point it at the create form with the id pre-filled instead — `NewTemplateView`
+already reads `presetId`:
+
+```tsx
+{
+  r.status !== 'invalid-id' && (
+    <Link
+      href={
+        r.status === 'ok'
+          ? `/templates/${r.id}`
+          : `/templates/new?id=${encodeURIComponent(r.id)}`
+      }
+      className="button"
+    >
+      {r.status === 'ok' ? 'Open' : 'Create'}
+    </Link>
+  );
+}
+```
+
+Then add the case to `src/app/templates/new/__tests__/View.test.tsx`:
+
+```tsx
+it('pre-fills the id the browse page handed it', () => {
+  render(<NewTemplateView presetId="toyota_supra_2020" />);
+  expect(screen.getByTestId('derived-id')).toHaveTextContent('toyota_supra_2020');
+});
+```
+
+- [ ] **Step 5: Full verification**
+
+Run: `npm test && npm run compile && npm run lint && npm run build`
+Expected: full suite green, typecheck clean, lint clean, production build succeeds.
+
+- [ ] **Step 6: Commit and open the PR**
+
+```bash
+git add src/app/templates
+git commit -m "feat(templates): create a template that does not exist yet
+
+Publishes immediately and attributed, because nothing points at a template
+nobody has created. If-None-Match makes an id that already exists a conflict
+with a link to it rather than a silent overwrite."
+
+git push -u origin template-editor
+gh pr create --title "Console template editor" --body "$(cat <<'BODY'
+The editor for the trim templates the extraction pipeline emits.
+
+Trims are columns, attributes are rows. Values shared across trims render
+muted; values that differ render at full contrast, so on the real Camry the eye
+lands on powertrain_type and fuel_tank_capacity_gal -- the pair the production
+record blended into one row describing two different cars.
+
+- `/templates` browses device definitions and says which have a template, which
+  do not yet, and which carry an id the schema cannot accept.
+- `/templates/<id>` edits one. Publish is disabled while the draft would fail
+  the worker, and the fault is named in the worker's own words.
+- `/templates/new` creates one.
+
+The write path holds DEFINITIONS_WRITE_TOKEN server-side, identifies the caller
+from the existing session, stamps `author` from it, and refuses a body that
+names its own author or version. Entitlement follows risk: creating harms
+nobody; editing a template 4,212 vehicles resolve to re-describes all of them.
+hardwareTemplateId is curator-only at every tier.
+
+Requires definitions-worker `template-cas` (schema route, compare-and-swap,
+generated types) to be deployed first.
+
+The proposal tier -- edit a referenced template you do not own, a curator
+merges -- is not built. Those callers get a read-only editor that says so.
+BODY
+)"
+```
+
+---
+
+## Sequencing
+
+```
+definitions-worker            dimo-developer-console
+  Task 1  schema route  ──────► Task 4  config + types + client
+  Task 2  CAS           ──┐          │
+  Task 3  generated types ┘          ├─► Task 5  divergence model
+                                     │      └─► Task 6  coercion + validation
+                                     │             └─► Task 7  the grid
+                                     ├─► Task 8  browse
+                                     └─► Task 9  server route (needs Task 2)
+                                            └─► Task 10 honesty surfaces
+                                                   └─► Task 11 editor page
+                                                          └─► Task 12 create
+```
+
+Tasks 5, 6, 7 and 8 need only Task 4 and can be built while the worker PR is in
+review. **Nothing in Phase 2 may be merged before Task 2 is deployed** — a save
+path without compare-and-swap is the defect this plan exists to avoid, not a
+staging step towards fixing it.
+
+## Not in this plan
+
+**Blockers that gate deployment but are not this feature's work:**
+
+- **Shrink dd-api.** `Create()` still `PUT`s `/definitions/<id>` and
+  `manifest()` still `GET`s `/manifest.json`; the new worker serves neither.
+  Every catalog miss and every search sync fails until those migrate. Nothing
+  here worsens it, and nothing here can ship to production before it lands.
+- **identity-api #188.** Two live defects: cold-start backoff never engages on a
+  5xx (`failedAttempt` receives a nil error), and the catalog refresh holds the
+  write lock so every read blocks — measured at 2.002 s against a healthy
+  snapshot. Task 8 and Task 9 both read identity on the request path, so this
+  is felt here even though it is not this plan's to fix.
+- **A production re-run of the extraction.** Every coverage number in
+  `VERIFY-trim-templates.md` came from prod styles against the _dev_ catalog.
+  14,145 templates and 2,729 orphans are artefacts of that mismatch and must not
+  be quoted for production.
+- **`TYPESENSE_COLLECTION` name collision** and **Typesense memory on a 439 MB
+  host that has OOM'd four times.** Both are cutover blockers in the worker's
+  DEPLOY.md.
+
+**Deferred to their own plans:**
+
+- **Proposals and curator merge.** The tier where someone edits a template they
+  do not own and a curator merges the result. It needs a proposal store the
+  worker does not have — a `p/<id>/<proposal>.json` prefix, a listing surface,
+  and a merge that is a normal CAS write with the curator as author. Never on a
+  timer. Until it exists, those callers get a read-only editor that says so.
+- **Revert.** Moves the head pointer, O(1). It is a curator action against
+  `t/<id>/meta.json`, which the worker does not currently serve; it needs a read
+  route for the version log first.
+- **An activity view over `GET /admin/history`.** When it is built: the route is
+  **paged** — `limit` defaults to 200, caps at 500, and returns a `next` cursor.
+  A consumer that reads only the first page silently truncates the record.
+- **A vocabulary editor.** `device-type-vehicle.json` is curated and changes
+  rarely; it is edited in the worker repo and deployed, not through Console.
+- **The 137 malformed production ids.** `subaru_tribeca-(ny/nj)_2008` is live
+  today. Whether to widen the id pattern or correct the ids is a product
+  decision; Task 8 shows them and says they cannot be edited, which is the
+  honest interim.
+
+## Verification checklist before opening either PR
+
+- [ ] `definitions-worker`: `npm test && npm run test:integration && npm run typecheck` — 200 unit, 41 integration, clean.
+- [ ] `dimo-developer-console`: `npm test && npm run compile && npm run lint && npm run build` — all clean.
+- [ ] `grep -rn "DEFINITIONS_WRITE_TOKEN" src/ | grep -v "src/services/definitions.ts"` returns nothing.
+- [ ] `git log --format=%B <base>..HEAD | grep -iE "co-authored-by|claude"` returns nothing, in both repos.
+- [ ] The integration test in Task 2 Step 6 was **run against the real R2 binding** and passed — not skipped, not deleted.
+- [ ] The entitlement assumption in Task 9 (an absent `author` means unowned) has been put to Yev and either confirmed or changed.
+
+## The question this plan is answering
+
+Five separate defects on this project shared one shape: correct behaviour that
+leaves no trace, or a guarantee that holds on the path under test and not the
+one beside it. For Console the equivalent question is _when the editor declines
+to save something, or quietly normalises it, does the person see that happen?_
+
+Where each task answers it:
+
+|         | Answer                                                                                                                                                                                                                  |
+| ------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| Task 2  | A losing writer gets a 412 naming the version to rebase onto, and an integration test proves it against the real binding rather than the fake that would pass either way.                                               |
+| Task 6  | Every difference between what was typed and what is stored produces a `Normalisation`. A reparsed number, trimmed whitespace, and a cleared attribute all leave a record.                                               |
+| Task 7  | A trim with no effective selector is marked in its header, as a validation state rather than a discovery at save. `—` distinguishes not-set from empty.                                                                 |
+| Task 8  | A definition with no template says so; an id the schema cannot accept says that instead. Neither is hidden as an error or as an empty result.                                                                           |
+| Task 9  | A body naming its own `author` or `version` is refused by name rather than stripped silently, and the forwarded `If-Match` is the client's, never the freshly-read one that would rebase a stale editor and return 200. |
+| Task 10 | The normalisation report, the selector warning, and the entitlement banner are three places the editor states what it did and what it will not do.                                                                      |
+| Task 11 | A conflict explains what happened and offers a reload. It never retries over the top of someone else's version.                                                                                                         |
diff --git a/package-lock.json b/package-lock.json
index ff49d886..5e412d25 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -81,6 +81,7 @@
         "husky": "^9.1.7",
         "jest": "^29.7.0",
         "jest-environment-jsdom": "^29.7.0",
+        "json-schema-to-typescript": "^15.0.4",
         "nock": "^13.5.6",
         "postcss": "^8.5.6",
         "postcss-nesting": "^12.1.5",
@@ -117,6 +118,23 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/@apidevtools/json-schema-ref-parser": {
+      "version": "11.9.3",
+      "resolved": "https://registry.npmjs.org/@apidevtools/json-schema-ref-parser/-/json-schema-ref-parser-11.9.3.tgz",
+      "integrity": "sha512-60vepv88RwcJtSHrD6MjIL6Ta3SOYbgfnkHb+ppAVK+o9mXprRtulx7VlRl3lN3bbvysAfCS7WMVfhUYemB0IQ==",
+      "dev": true,
+      "dependencies": {
+        "@jsdevtools/ono": "^7.1.3",
+        "@types/json-schema": "^7.0.15",
+        "js-yaml": "^4.1.0"
+      },
+      "engines": {
+        "node": ">= 16"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/philsturgeon"
+      }
+    },
     "node_modules/@apollo/client": {
       "version": "3.14.0",
       "resolved": "https://registry.npmjs.org/@apollo/client/-/client-3.14.0.tgz",
@@ -4282,6 +4300,12 @@
         "@jridgewell/sourcemap-codec": "^1.4.14"
       }
     },
+    "node_modules/@jsdevtools/ono": {
+      "version": "7.1.3",
+      "resolved": "https://registry.npmjs.org/@jsdevtools/ono/-/ono-7.1.3.tgz",
+      "integrity": "sha512-4JQNk+3mVzK3xh2rqd6RB4J46qUR19azEHBneZyTZM+c456qOrbbM/5xcR8huNCCcbVt7+UmizG6GuUvPvKUYg==",
+      "dev": true
+    },
     "node_modules/@lit-labs/ssr-dom-shim": {
       "version": "1.4.0",
       "resolved": "https://registry.npmjs.org/@lit-labs/ssr-dom-shim/-/ssr-dom-shim-1.4.0.tgz",
@@ -22300,6 +22324,29 @@
       "integrity": "sha512-es94M3nTIfsEPisRafak+HDLfHXnKBhV3vU5eqPcS3flIWqcxJWgXHXiey3YrpaNsanY5ei1VoYEbOzijuq9BA==",
       "license": "(AFL-2.1 OR BSD-3-Clause)"
     },
+    "node_modules/json-schema-to-typescript": {
+      "version": "15.0.4",
+      "resolved": "https://registry.npmjs.org/json-schema-to-typescript/-/json-schema-to-typescript-15.0.4.tgz",
+      "integrity": "sha512-Su9oK8DR4xCmDsLlyvadkXzX6+GGXJpbhwoLtOGArAG61dvbW4YQmSEno2y66ahpIdmLMg6YUf/QHLgiwvkrHQ==",
+      "dev": true,
+      "dependencies": {
+        "@apidevtools/json-schema-ref-parser": "^11.5.5",
+        "@types/json-schema": "^7.0.15",
+        "@types/lodash": "^4.17.7",
+        "is-glob": "^4.0.3",
+        "js-yaml": "^4.1.0",
+        "lodash": "^4.17.21",
+        "minimist": "^1.2.8",
+        "prettier": "^3.2.5",
+        "tinyglobby": "^0.2.9"
+      },
+      "bin": {
+        "json2ts": "dist/src/cli.js"
+      },
+      "engines": {
+        "node": ">=16.0.0"
+      }
+    },
     "node_modules/json-schema-traverse": {
       "version": "0.4.1",
       "resolved": "https://registry.npmjs.org/json-schema-traverse/-/json-schema-traverse-0.4.1.tgz",
diff --git a/package.json b/package.json
index 795b2168..1b8beb9c 100644
--- a/package.json
+++ b/package.json
@@ -3,7 +3,7 @@
   "version": "0.1.0",
   "private": true,
   "scripts": {
-    "prebuild": "npm run lint",
+    "prebuild": "npm run lint && npm run check:template-types",
     "build": "next build",
     "predev": "npm run compile",
     "dev": "next dev",
@@ -15,6 +15,8 @@
     "test:update-snap": "jest -u",
     "test:watch": "jest --watch",
     "compile": "graphql-codegen --config src/codegen.ts",
+    "gen:template-types": "node scripts/gen-template-types.mjs",
+    "check:template-types": "node scripts/gen-template-types.mjs --check",
     "prepare": "husky"
   },
   "dependencies": {
@@ -91,6 +93,7 @@
     "husky": "^9.1.7",
     "jest": "^29.7.0",
     "jest-environment-jsdom": "^29.7.0",
+    "json-schema-to-typescript": "^15.0.4",
     "nock": "^13.5.6",
     "postcss": "^8.5.6",
     "postcss-nesting": "^12.1.5",
diff --git a/scripts/gen-template-types.mjs b/scripts/gen-template-types.mjs
new file mode 100644
index 00000000..7ea3a6aa
--- /dev/null
+++ b/scripts/gen-template-types.mjs
@@ -0,0 +1,94 @@
+#!/usr/bin/env node
+// The template contract is definitions-worker/schema/template.schema.json,
+// served at <definitionsWorkerUrl>/schema/. Console generates from it rather
+// than hand-writing a third copy (the worker's TS and dd-api's Go are the
+// other two).
+//
+// The generator reads a VENDORED copy of the schema, not the network. Two
+// reasons. A generator whose input can change underneath it produces output
+// nobody can reproduce -- the same command on the same commit gives different
+// answers depending on what is deployed that minute. And drift is only
+// reviewable if it appears in a diff: `--from` rewrites the vendored schema
+// alongside the types, so a contract change shows up as both files moving
+// together in the same commit.
+//
+//   npm run gen:template-types                 regenerate types from the vendored schema
+//   npm run gen:template-types -- --from <url|path>   pull a new contract, then regenerate
+//   npm run check:template-types               fail if the committed types are stale
+import { compile } from 'json-schema-to-typescript';
+import { writeFile, readFile, mkdir } from 'node:fs/promises';
+import { fileURLToPath } from 'node:url';
+
+const SCHEMA = new URL('../src/types/generated/template.schema.json', import.meta.url);
+const OUT = new URL('../src/types/generated/template.ts', import.meta.url);
+
+const BANNER = `/* eslint-disable */
+// GENERATED by scripts/gen-template-types.mjs from
+// src/types/generated/template.schema.json, vendored from
+// definitions-worker/schema/template.schema.json. Do not edit.
+`;
+
+async function load(source) {
+  if (source === undefined) return JSON.parse(await readFile(SCHEMA, 'utf8'));
+  if (source.startsWith('http')) {
+    const resp = await fetch(source);
+    if (!resp.ok) throw new Error(`${source} returned ${resp.status}`);
+    return resp.json();
+  }
+  return JSON.parse(await readFile(source, 'utf8'));
+}
+
+// Exported so the drift guard runs the real generator rather than a
+// reimplementation of it -- a guard that regenerates differently from the
+// generator tests nothing.
+export async function generate(source) {
+  const schema = await load(source);
+  const body = await compile(schema, 'Template', {
+    bannerComment: '',
+    additionalProperties: false,
+    // Mirrors definitions-worker/scripts/gen-types.mjs: minItems on trims
+    // otherwise generates [Trim, ...Trim[]], which no .map() result can be
+    // assigned back to.
+    ignoreMinAndMaxItems: true,
+    style: { singleQuote: true, semi: true, printWidth: 90 },
+  });
+  return { schema, types: BANNER + body };
+}
+
+const fromFlag = process.argv.indexOf('--from');
+const source = fromFlag !== -1 ? process.argv[fromFlag + 1] : undefined;
+const check = process.argv.includes('--check');
+
+if (check && source !== undefined) {
+  console.error(
+    '--check verifies the committed output against the vendored schema; it does not take --from',
+  );
+  process.exit(2);
+}
+
+const { schema, types } = await generate(source);
+
+if (check) {
+  const committed = await readFile(OUT, 'utf8').catch(() => null);
+  if (committed === types) {
+    console.log('src/types/generated/template.ts is up to date with the vendored schema');
+    process.exit(0);
+  }
+  console.error(
+    committed === null
+      ? 'src/types/generated/template.ts is missing.'
+      : 'src/types/generated/template.ts is stale: the vendored schema no longer produces it.',
+  );
+  console.error('Run `npm run gen:template-types` and commit the result.');
+  process.exit(1);
+}
+
+await mkdir(new URL('../src/types/generated/', import.meta.url), { recursive: true });
+// The schema is rewritten only when one was fetched: a plain regeneration must
+// not touch the contract it read.
+if (source !== undefined) {
+  await writeFile(SCHEMA, `${JSON.stringify(schema, null, 2)}\n`);
+  console.log(`vendored ${fileURLToPath(SCHEMA)} from ${source}`);
+}
+await writeFile(OUT, types);
+console.log(`wrote ${fileURLToPath(OUT)}`);
diff --git a/src/app/api/templates/[id]/route.ts b/src/app/api/templates/[id]/route.ts
new file mode 100644
index 00000000..e481e4b1
--- /dev/null
+++ b/src/app/api/templates/[id]/route.ts
@@ -0,0 +1,175 @@
+import { NextRequest, NextResponse } from 'next/server';
+import * as Sentry from '@sentry/nextjs';
+import {
+  fetchTemplate,
+  fetchVocabulary,
+  publishTemplate,
+  type Precondition,
+} from '@/services/definitions';
+import {
+  countMintedVehicles,
+  curatorAddresses,
+  manufacturerOwner,
+  resolveCaller,
+  resolveEntitlement,
+} from '@/services/templateEntitlement';
+import type { TemplatePayload } from '@/types/template';
+
+// Server-owned. definitions-worker rejects them as unexpected top-level keys,
+// and `author` is stamped below from the session. A body carrying any of them
+// is refused by name rather than silently stripped: a client that thinks it set
+// the author and was quietly overruled has learned nothing.
+const SERVER_OWNED = ['version', 'createdAt', 'updatedAt', 'author'] as const;
+
+type Params = { params: Promise<{ id: string }> };
+
+async function entitlementFor(caller: string, id: string) {
+  const template = await fetchTemplate(id);
+  const entitlement = await resolveEntitlement({
+    caller,
+    template,
+    countMintedVehicles,
+    manufacturerOwner,
+    curators: curatorAddresses(),
+  });
+  return { template, entitlement };
+}
+
+export async function GET(_req: NextRequest, { params }: Params) {
+  const { id } = await params;
+  const caller = await resolveCaller();
+  if (!caller) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+
+  try {
+    const [{ template, entitlement }, vocabulary] = await Promise.all([
+      entitlementFor(caller.address, id),
+      fetchVocabulary(),
+    ]);
+    return NextResponse.json({ template, vocabulary, entitlement });
+  } catch (err) {
+    Sentry.captureException(err);
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : 'Failed to load template' },
+      { status: 502 },
+    );
+  }
+}
+
+export async function PUT(req: NextRequest, { params }: Params) {
+  const { id } = await params;
+  const caller = await resolveCaller();
+  if (!caller) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+
+  let submitted: Record<string, unknown>;
+  try {
+    submitted = (await req.json()) as Record<string, unknown>;
+  } catch {
+    return NextResponse.json({ error: 'body is not valid JSON' }, { status: 400 });
+  }
+
+  for (const field of SERVER_OWNED) {
+    if (field in submitted) {
+      return NextResponse.json(
+        {
+          error: `${field} is set by the server, not by the client — remove it from the body`,
+        },
+        { status: 400 },
+      );
+    }
+  }
+  if (submitted.id !== id) {
+    return NextResponse.json(
+      { error: `body id does not match path id "${id}"` },
+      { status: 400 },
+    );
+  }
+
+  try {
+    const { template, entitlement } = await entitlementFor(caller.address, id);
+
+    if (!entitlement.canPublish) {
+      return NextResponse.json(
+        { error: entitlement.reason, entitlement },
+        { status: 403 },
+      );
+    }
+
+    // hardwareTemplateId decides what hardware ships. It is not a vehicle
+    // attribute and it is never open, at any tier.
+    const submittedHw = submitted.hardwareTemplateId as string | undefined;
+    if (
+      submittedHw !== template?.hardwareTemplateId &&
+      !entitlement.canSetHardwareTemplateId
+    ) {
+      return NextResponse.json(
+        {
+          error:
+            'hardwareTemplateId is set by DIMO only — it decides what hardware ships, and is not a vehicle attribute',
+          entitlement,
+        },
+        { status: 403 },
+      );
+    }
+
+    // The precondition comes from the CLIENT, never from the template we just
+    // read. Using the fresh version would rebase a stale editor onto whatever
+    // landed while it was open -- a lost update with a 200 on it, which is the
+    // exact failure the worker's CAS exists to make impossible.
+    let precondition: Precondition;
+    if (template === null) {
+      precondition = { kind: 'create' };
+    } else {
+      const ifMatch = req.headers.get('if-match');
+      const version = Number((ifMatch ?? '').replace(/^W\//, '').replace(/"/g, ''));
+      if (!Number.isInteger(version) || version < 1) {
+        return NextResponse.json(
+          {
+            error:
+              'If-Match is required when editing an existing template: send the version you loaded',
+          },
+          { status: 428 },
+        );
+      }
+      precondition = { kind: 'update', version };
+    }
+
+    // TemplatePayload deliberately excludes `author` -- it is not client input.
+    // The wire body does carry it, stamped here, which is the one place the two
+    // shapes differ.
+    const payload = {
+      ...submitted,
+      author: caller.address,
+    } as unknown as TemplatePayload;
+    const result = await publishTemplate(id, payload, precondition);
+
+    if (result.ok) return NextResponse.json({ template: result.template });
+    if (result.kind === 'validation') {
+      return NextResponse.json({ errors: result.errors }, { status: 422 });
+    }
+    if (result.kind === 'conflict') {
+      return NextResponse.json(
+        {
+          error: 'This template changed while you were editing it.',
+          conflict: { expected: result.expected, actual: result.actual },
+        },
+        { status: 409 },
+      );
+    }
+    if (result.kind === 'too-large') {
+      return NextResponse.json(
+        {
+          error: `This template is ${result.bytes} bytes; the limit is ${result.limit}.`,
+        },
+        { status: 413 },
+      );
+    }
+    Sentry.captureMessage(`definitions-worker ${result.status}: ${result.message}`);
+    return NextResponse.json({ error: result.message }, { status: 502 });
+  } catch (err) {
+    Sentry.captureException(err);
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : 'Failed to publish template' },
+      { status: 502 },
+    );
+  }
+}
diff --git a/src/app/api/templates/route.ts b/src/app/api/templates/route.ts
new file mode 100644
index 00000000..0aba7278
--- /dev/null
+++ b/src/app/api/templates/route.ts
@@ -0,0 +1,112 @@
+import { NextRequest, NextResponse } from 'next/server';
+import config from '@/config';
+import { fetchTemplate } from '@/services/definitions';
+
+// definitions-worker/schema/template.schema.json, properties.id.pattern.
+const ID_RE = /^[a-z0-9][a-z0-9._&+-]*_[a-z0-9._&+-]+_[0-9]{4}$/;
+
+// Identity's DeviceDefinitionFilter takes model and year only, and
+// ManufacturerBy takes a name or a slug -- so "make" here is whichever the
+// person typed, tried as a slug first because that is what a template id
+// carries.
+const SEARCH = `
+  query TemplateSearch($by: ManufacturerBy!, $filterBy: DeviceDefinitionFilter, $first: Int!) {
+    manufacturer(by: $by) {
+      name
+      tokenId
+      deviceDefinitions(filterBy: $filterBy, first: $first) {
+        nodes { deviceDefinitionId model year }
+      }
+    }
+  }`;
+
+const PAGE = 25;
+
+export interface SearchResult {
+  id: string;
+  model: string;
+  year: number;
+  status: 'ok' | 'missing' | 'invalid-id';
+  version?: number;
+  trims?: number;
+}
+
+async function queryIdentity(
+  by: Record<string, string>,
+  filterBy: Record<string, unknown>,
+) {
+  const resp = await fetch(config.identityApiUrl, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ query: SEARCH, variables: { by, filterBy, first: PAGE } }),
+    cache: 'no-store',
+  });
+  if (!resp.ok) throw new Error(`identity-api returned ${resp.status}`);
+  const json = (await resp.json()) as {
+    data?: {
+      manufacturer?: {
+        name: string;
+        tokenId: number;
+        deviceDefinitions: {
+          nodes: { deviceDefinitionId: string; model: string; year: number }[];
+        };
+      } | null;
+    };
+  };
+  return json.data?.manufacturer ?? null;
+}
+
+export async function GET(req: NextRequest) {
+  const make = req.nextUrl.searchParams.get('make');
+  const model = req.nextUrl.searchParams.get('model');
+  const yearParam = req.nextUrl.searchParams.get('year');
+  if (!make) return NextResponse.json({ error: 'make is required' }, { status: 400 });
+
+  const filterBy: Record<string, unknown> = {};
+  if (model) filterBy.model = model;
+  if (yearParam) {
+    const year = Number(yearParam);
+    if (!Number.isInteger(year)) {
+      return NextResponse.json({ error: 'year must be an integer' }, { status: 400 });
+    }
+    filterBy.year = year;
+  }
+
+  try {
+    const manufacturer =
+      (await queryIdentity({ slug: make.toLowerCase() }, filterBy)) ??
+      (await queryIdentity({ name: make }, filterBy));
+    if (!manufacturer) return NextResponse.json({ manufacturer: null, results: [] });
+
+    const results = await Promise.all(
+      manufacturer.deviceDefinitions.nodes.map(async (node): Promise<SearchResult> => {
+        const base = { id: node.deviceDefinitionId, model: node.model, year: node.year };
+        // 137 ids in production cannot be template ids -- subaru_tribeca-(ny/nj)_2008
+        // is live today. Saying so beats asking the worker a question whose
+        // answer would be a misleading 404.
+        if (!ID_RE.test(node.deviceDefinitionId))
+          return { ...base, status: 'invalid-id' };
+        const template = await fetchTemplate(node.deviceDefinitionId);
+        // A missing template is a real state: the import has not run in
+        // production, and 5,152 of the emitted set carry no attributes.
+        if (!template) return { ...base, status: 'missing' };
+        return {
+          ...base,
+          status: 'ok',
+          version: template.version,
+          trims: template.trims.length,
+        };
+      }),
+    );
+
+    return NextResponse.json({
+      manufacturer: { name: manufacturer.name, tokenId: manufacturer.tokenId },
+      results,
+    });
+  } catch (err) {
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : 'search failed' },
+      { status: 502 },
+    );
+  }
+}
diff --git a/src/app/templates/[id]/__tests__/View.test.tsx b/src/app/templates/[id]/__tests__/View.test.tsx
new file mode 100644
index 00000000..4f56d9b7
--- /dev/null
+++ b/src/app/templates/[id]/__tests__/View.test.tsx
@@ -0,0 +1,153 @@
+import { render, screen, fireEvent, waitFor, within } from '@testing-library/react';
+import camry from '@/utils/__fixtures__/toyota_camry_2020.json';
+import { vehicleVocab } from '@/utils/__fixtures__/vehicleVocab';
+import { TemplateEditorView } from '../components/View';
+import type { Template } from '@/types/template';
+
+const t = camry as unknown as Template;
+
+const publish = jest.fn();
+const refetch = jest.fn();
+
+// A mutable bundle rather than a second module mock: the read-only branch is a
+// different entitlement, not a different module, and the component must derive
+// it from the data it is given.
+let bundle: {
+  template: Template;
+  vocabulary: typeof vehicleVocab;
+  entitlement: {
+    kind: string;
+    canPublish: boolean;
+    canSetHardwareTemplateId: boolean;
+    mintedVehicles: number;
+    reason: string;
+  };
+};
+
+jest.mock('@/hooks/queries/useTemplate', () => ({
+  useTemplate: () => ({ data: bundle, isLoading: false, error: null, refetch }),
+  usePublishTemplate: () => ({ mutateAsync: publish, isPending: false }),
+}));
+
+const authorBundle = () => ({
+  template: t,
+  vocabulary: vehicleVocab,
+  entitlement: {
+    kind: 'author',
+    canPublish: true,
+    canSetHardwareTemplateId: false,
+    mintedVehicles: 0,
+    reason: 'No vehicle references this template yet.',
+  },
+});
+
+/** Publish is disabled until the draft differs from what was loaded. */
+const edit = () => {
+  const input = within(screen.getByTestId('cell-mpg_city-0')).getByRole('textbox');
+  fireEvent.change(input, { target: { value: '27' } });
+  fireEvent.blur(input);
+};
+
+describe('TemplateEditorView', () => {
+  beforeEach(() => {
+    bundle = authorBundle();
+    publish.mockReset().mockResolvedValue({ ...t, version: t.version + 1 });
+    refetch.mockReset();
+  });
+
+  it('shows the current version and the author of the version it loaded', () => {
+    render(<TemplateEditorView id={t.id} />);
+    expect(screen.getByText(new RegExp(`v${t.version}`))).toBeInTheDocument();
+  });
+
+  it('leaves publish disabled until something actually changed', () => {
+    render(<TemplateEditorView id={t.id} />);
+    expect(screen.getByRole('button', { name: /^publish/i })).toBeDisabled();
+    edit();
+    expect(screen.getByRole('button', { name: /^publish/i })).toBeEnabled();
+  });
+
+  it('refuses to publish while the draft would fail the worker, and names the fault', async () => {
+    render(<TemplateEditorView id={t.id} />);
+    fireEvent.click(screen.getByRole('button', { name: /add trim/i }));
+    expect(await screen.findByText(/selectors are required/)).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /^publish/i })).toBeDisabled();
+    expect(publish).not.toHaveBeenCalled();
+  });
+
+  it('sends the version it loaded as the precondition, and never the payload server fields', async () => {
+    render(<TemplateEditorView id={t.id} />);
+    edit();
+    fireEvent.click(screen.getByRole('button', { name: /^publish/i }));
+    await waitFor(() => expect(publish).toHaveBeenCalled());
+    const { payload, version } = publish.mock.calls[0][0];
+    expect(version).toBe(t.version);
+    expect(payload.version).toBeUndefined();
+    expect(payload.author).toBeUndefined();
+    expect(payload.createdAt).toBeUndefined();
+  });
+
+  it('surfaces the worker validation errors verbatim', async () => {
+    publish.mockRejectedValue({
+      status: 422,
+      errors: ['trim LE: "mpg_city" above maximum 200'],
+    });
+    render(<TemplateEditorView id={t.id} />);
+    edit();
+    fireEvent.click(screen.getByRole('button', { name: /^publish/i }));
+    expect(
+      await screen.findByText('trim LE: "mpg_city" above maximum 200'),
+    ).toBeInTheDocument();
+  });
+
+  it('explains a conflict instead of retrying over the top of it', async () => {
+    publish.mockRejectedValue({ status: 409, conflict: { expected: 10, actual: 12 } });
+    render(<TemplateEditorView id={t.id} />);
+    edit();
+    fireEvent.click(screen.getByRole('button', { name: /^publish/i }));
+    expect(await screen.findByRole('alert')).toHaveTextContent('version 12');
+    expect(screen.getByRole('button', { name: /reload/i })).toBeInTheDocument();
+    expect(publish).toHaveBeenCalledTimes(1);
+  });
+
+  it('reports the normalisation when a typed value is not what gets stored', () => {
+    render(<TemplateEditorView id={t.id} />);
+    const input = within(screen.getByTestId('cell-fuel_tank_capacity_gal-0')).getByRole(
+      'textbox',
+    );
+    fireEvent.change(input, { target: { value: '16.000000' } });
+    fireEvent.blur(input);
+    expect(
+      screen.getByText(/What the editor changed that you did not type/),
+    ).toBeInTheDocument();
+    expect(screen.getByText(/stored as the number 16/)).toBeInTheDocument();
+  });
+
+  it('is read only, with no publish button, when a proposal is required', () => {
+    bundle = {
+      ...authorBundle(),
+      entitlement: {
+        kind: 'proposal-required',
+        canPublish: false,
+        canSetHardwareTemplateId: false,
+        mintedVehicles: 4212,
+        reason: '4,212 minted vehicles resolve to this template.',
+      },
+    };
+    render(<TemplateEditorView id={t.id} />);
+    expect(screen.queryByRole('button', { name: /^publish/i })).toBeNull();
+    expect(screen.queryByRole('button', { name: /add trim/i })).toBeNull();
+    expect(screen.queryByRole('button', { name: /remove trim/i })).toBeNull();
+    // The grid renders values as text rather than fields, and the selector
+    // editor keeps its labelled fields but marks every one readonly. The
+    // guarantee is that nothing on the page is editable, not that nothing has
+    // a textbox role.
+    expect(
+      within(screen.getByTestId('cell-mpg_city-0')).queryByRole('textbox'),
+    ).toBeNull();
+    expect(screen.queryAllByRole('combobox')).toHaveLength(0);
+    screen
+      .queryAllByRole('textbox')
+      .forEach((field) => expect(field).toHaveAttribute('readonly'));
+  });
+});
diff --git a/src/app/templates/[id]/components/View/View.tsx b/src/app/templates/[id]/components/View/View.tsx
new file mode 100644
index 00000000..c400d435
--- /dev/null
+++ b/src/app/templates/[id]/components/View/View.tsx
@@ -0,0 +1,188 @@
+'use client';
+
+import React, { useEffect, useMemo, useState, type FC } from 'react';
+import { Button } from '@/components/Button';
+import { QueryPageWrapper } from '@/components/QueryPageWrapper';
+import { TrimGrid } from '@/components/TemplateEditor/TrimGrid';
+import { TrimSelectorEditor } from '@/components/TemplateEditor/TrimSelectorEditor';
+import { NormalisationPanel } from '@/components/TemplateEditor/NormalisationPanel';
+import { EntitlementBanner } from '@/components/TemplateEditor/EntitlementBanner';
+import {
+  useTemplate,
+  usePublishTemplate,
+  type PublishFailure,
+} from '@/hooks/queries/useTemplate';
+import { addTrim, toPayload } from '@/utils/templateGrid';
+import { validateDraft } from '@/utils/templateValidate';
+import type { Normalisation } from '@/utils/templateCoerce';
+import type { Template } from '@/types/template';
+
+interface Props {
+  id: string;
+}
+
+export const TemplateEditorView: FC<Props> = ({ id }) => {
+  const { data, isLoading, error, refetch } = useTemplate(id);
+  const publish = usePublishTemplate(id);
+
+  const [draft, setDraft] = useState<Template | null>(null);
+  const [notes, setNotes] = useState<Normalisation[]>([]);
+  const [serverErrors, setServerErrors] = useState<string[]>([]);
+  const [conflict, setConflict] = useState<{
+    expected: number | null;
+    actual: number;
+  } | null>(null);
+  const [published, setPublished] = useState<number | null>(null);
+
+  // The version loaded, held apart from the draft: it is what If-Match sends,
+  // and it must not move when the draft does.
+  const loadedVersion = data?.template?.version ?? null;
+  const readOnly = !(data?.entitlement.canPublish ?? false);
+
+  useEffect(() => {
+    if (data?.template && draft === null) setDraft(data.template);
+  }, [data, draft]);
+
+  const dirty =
+    draft !== null &&
+    data?.template !== null &&
+    JSON.stringify(draft) !== JSON.stringify(data?.template);
+
+  useEffect(() => {
+    if (!dirty) return undefined;
+    const warn = (e: BeforeUnloadEvent) => {
+      e.preventDefault();
+    };
+    window.addEventListener('beforeunload', warn);
+    return () => window.removeEventListener('beforeunload', warn);
+  }, [dirty]);
+
+  const localErrors = useMemo(
+    () => (draft && data ? validateDraft(draft, data.vocabulary) : []),
+    [draft, data],
+  );
+
+  const onPublish = async () => {
+    if (!draft || loadedVersion === null) return;
+    setServerErrors([]);
+    setConflict(null);
+    try {
+      const result = await publish.mutateAsync({
+        payload: toPayload(draft),
+        version: loadedVersion,
+      });
+      setPublished(result.version);
+      setNotes([]);
+      await refetch();
+      setDraft(null);
+    } catch (err) {
+      const failure = err as PublishFailure;
+      if (failure.status === 409 && failure.conflict) setConflict(failure.conflict);
+      else setServerErrors(failure.errors ?? [failure.message ?? 'Publish failed']);
+    }
+  };
+
+  return (
+    <QueryPageWrapper
+      loading={isLoading}
+      error={error ?? undefined}
+      customErrorMessage="Could not load this template"
+    >
+      {draft && data && (
+        <div className="flex flex-col gap-6">
+          <header className="flex flex-wrap items-center justify-between gap-3">
+            <div className="flex flex-col">
+              <h1 className="text-white">
+                {draft.manufacturer.name} {draft.model} {draft.year}
+              </h1>
+              <span className="font-mono text-xs text-white/50">
+                {draft.id} · v{loadedVersion}
+                {data.template?.author && ` · last published by ${data.template.author}`}
+              </span>
+            </div>
+            {!readOnly && (
+              <div className="flex items-center gap-2">
+                <Button className="dark" onClick={() => setDraft(addTrim(draft, ''))}>
+                  Add trim
+                </Button>
+                <Button
+                  onClick={onPublish}
+                  loading={publish.isPending}
+                  disabled={localErrors.length > 0 || !dirty}
+                >
+                  Publish
+                </Button>
+              </div>
+            )}
+          </header>
+
+          <EntitlementBanner entitlement={data.entitlement} />
+
+          {published !== null && (
+            <p className="text-primary-300">Published version {published}.</p>
+          )}
+
+          {conflict && (
+            <div
+              role="alert"
+              className="flex flex-col gap-2 rounded-xl border border-red-400/40 bg-surface-raised p-4"
+            >
+              <span className="text-red-400">
+                This template moved to version {conflict.actual} while you were editing
+                version {conflict.expected}.
+              </span>
+              <span className="text-white/70">
+                Your draft has not been discarded and nothing was published. Reload to see
+                the current version, then re-apply your changes.
+              </span>
+              <div>
+                <Button
+                  className="dark"
+                  onClick={() => {
+                    setDraft(null);
+                    setConflict(null);
+                    refetch();
+                  }}
+                >
+                  Reload
+                </Button>
+              </div>
+            </div>
+          )}
+
+          {(localErrors.length > 0 || serverErrors.length > 0) && (
+            <ul className="flex flex-col gap-1 rounded-xl border border-red-400/40 bg-surface-raised p-4">
+              {[...serverErrors, ...localErrors].map((e) => (
+                <li key={e} className="text-red-400">
+                  {e}
+                </li>
+              ))}
+            </ul>
+          )}
+
+          <NormalisationPanel notes={notes} onDismiss={() => setNotes([])} />
+
+          <TrimGrid
+            template={draft}
+            vocab={data.vocabulary}
+            readOnly={readOnly}
+            onChange={setDraft}
+            onNormalise={(note) => setNotes((prev) => [...prev, note])}
+          />
+
+          <div className="flex flex-col gap-3">
+            {draft.trims.map((trim, i) => (
+              <TrimSelectorEditor
+                key={`${trim.name}-${i}`}
+                template={draft}
+                trimIndex={i}
+                readOnly={readOnly}
+                onChange={setDraft}
+              />
+            ))}
+          </div>
+        </div>
+      )}
+    </QueryPageWrapper>
+  );
+};
diff --git a/src/app/templates/[id]/components/View/index.ts b/src/app/templates/[id]/components/View/index.ts
new file mode 100644
index 00000000..450cf3c6
--- /dev/null
+++ b/src/app/templates/[id]/components/View/index.ts
@@ -0,0 +1 @@
+export * from './View';
diff --git a/src/app/templates/[id]/page.tsx b/src/app/templates/[id]/page.tsx
new file mode 100644
index 00000000..50802b26
--- /dev/null
+++ b/src/app/templates/[id]/page.tsx
@@ -0,0 +1,16 @@
+'use client';
+
+import React, { Suspense, use, type FC } from 'react';
+
+import { TemplateEditorView } from './components/View';
+
+const TemplatePage: FC<{ params: Promise<{ id: string }> }> = ({ params }) => {
+  const { id } = use(params);
+  return (
+    <Suspense fallback={<div>Loading...</div>}>
+      <TemplateEditorView id={decodeURIComponent(id)} />
+    </Suspense>
+  );
+};
+
+export default TemplatePage;
diff --git a/src/app/templates/layout.ts b/src/app/templates/layout.ts
new file mode 100644
index 00000000..17e6dd0a
--- /dev/null
+++ b/src/app/templates/layout.ts
@@ -0,0 +1,3 @@
+import { AuthorizedLayout } from '@/layouts/AuthorizedLayout';
+
+export default AuthorizedLayout;
diff --git a/src/app/templates/new/__tests__/View.test.tsx b/src/app/templates/new/__tests__/View.test.tsx
new file mode 100644
index 00000000..39e3a333
--- /dev/null
+++ b/src/app/templates/new/__tests__/View.test.tsx
@@ -0,0 +1,78 @@
+import { render, screen, fireEvent, waitFor } from '@testing-library/react';
+import { NewTemplateView } from '../components/View';
+
+const publish = jest.fn();
+const push = jest.fn();
+
+jest.mock('@/hooks/queries/useTemplate', () => ({
+  usePublishTemplate: () => ({ mutateAsync: publish, isPending: false }),
+}));
+jest.mock('next/navigation', () => ({ useRouter: () => ({ push }) }));
+
+const fill = (label: RegExp, value: string) =>
+  fireEvent.change(screen.getByLabelText(label), { target: { value } });
+
+describe('NewTemplateView', () => {
+  beforeEach(() => {
+    publish.mockReset().mockResolvedValue({ id: 'ineos_grenadier_2024', version: 1 });
+    push.mockReset();
+  });
+
+  it('builds the id from make slug, model slug and year, and shows it', () => {
+    render(<NewTemplateView />);
+    fill(/make slug/i, 'ineos');
+    fill(/model slug/i, 'grenadier');
+    fill(/^year/i, '2024');
+    expect(screen.getByTestId('derived-id')).toHaveTextContent('ineos_grenadier_2024');
+  });
+
+  it('pre-fills the id the browse page handed it', () => {
+    render(<NewTemplateView presetId="toyota_supra_2020" />);
+    expect(screen.getByTestId('derived-id')).toHaveTextContent('toyota_supra_2020');
+  });
+
+  it('refuses a slug the id pattern cannot accept, before any request', async () => {
+    render(<NewTemplateView />);
+    fill(/make slug/i, 'Subaru');
+    fill(/model slug/i, 'tribeca-(ny/nj)');
+    fill(/^year/i, '2008');
+    fireEvent.click(screen.getByRole('button', { name: /create/i }));
+    expect(
+      await screen.findByText('id must be <make>_<model>_<year>'),
+    ).toBeInTheDocument();
+    expect(publish).not.toHaveBeenCalled();
+  });
+
+  it('creates with a null precondition so the route sends If-None-Match', async () => {
+    render(<NewTemplateView />);
+    fill(/make slug/i, 'ineos');
+    fill(/model slug/i, 'grenadier');
+    fill(/^year/i, '2024');
+    fill(/manufacturer name/i, 'INEOS');
+    fill(/model name/i, 'Grenadier');
+    fill(/first trim/i, 'Trialmaster');
+    fireEvent.click(screen.getByRole('button', { name: /create/i }));
+    await waitFor(() => expect(publish).toHaveBeenCalled());
+    expect(publish.mock.calls[0][0].version).toBeNull();
+    expect(publish.mock.calls[0][0].payload.trims).toEqual([
+      { name: 'Trialmaster', attributes: {} },
+    ]);
+  });
+
+  it('says the template already exists rather than reporting a generic failure', async () => {
+    publish.mockRejectedValue({ status: 409, conflict: { expected: null, actual: 4 } });
+    render(<NewTemplateView />);
+    fill(/make slug/i, 'toyota');
+    fill(/model slug/i, 'camry');
+    fill(/^year/i, '2020');
+    fill(/manufacturer name/i, 'Toyota');
+    fill(/model name/i, 'Camry');
+    fill(/first trim/i, 'LE');
+    fireEvent.click(screen.getByRole('button', { name: /create/i }));
+    expect(await screen.findByRole('alert')).toHaveTextContent('already exists');
+    expect(screen.getByRole('link', { name: /open it/i })).toHaveAttribute(
+      'href',
+      '/templates/toyota_camry_2020',
+    );
+  });
+});
diff --git a/src/app/templates/new/components/View/View.tsx b/src/app/templates/new/components/View/View.tsx
new file mode 100644
index 00000000..df4d35b4
--- /dev/null
+++ b/src/app/templates/new/components/View/View.tsx
@@ -0,0 +1,143 @@
+'use client';
+
+import React, { useMemo, useState, type FC } from 'react';
+import Link from 'next/link';
+import { useRouter } from 'next/navigation';
+import { Button } from '@/components/Button';
+import { usePublishTemplate, type PublishFailure } from '@/hooks/queries/useTemplate';
+import { validateDraft } from '@/utils/templateValidate';
+import { toPayload } from '@/utils/templateGrid';
+import type { DeviceType, Template } from '@/types/template';
+
+// A create form needs no vocabulary: a new template starts with no attributes
+// at all -- 5,152 of the emitted set are attribute-free and that is a real,
+// valid template. The editor fetches the live vocabulary once the template
+// exists.
+const EMPTY_VOCAB: DeviceType = { id: 'vehicle', name: 'Vehicle', attributes: [] };
+
+/** `presetId` comes from the browse page's Create link, e.g. toyota_supra_2020. */
+export const NewTemplateView: FC<{ presetId?: string }> = ({ presetId }) => {
+  const router = useRouter();
+  const [form, setForm] = useState(() => {
+    const parts = (presetId ?? '').split('_');
+    const blank = {
+      makeSlug: '',
+      modelSlug: '',
+      year: '',
+      manufacturerName: '',
+      modelName: '',
+      trimName: '',
+    };
+    return parts.length === 3
+      ? { ...blank, makeSlug: parts[0], modelSlug: parts[1], year: parts[2] }
+      : blank;
+  });
+  const [errors, setErrors] = useState<string[]>([]);
+  const [exists, setExists] = useState(false);
+
+  const id = `${form.makeSlug}_${form.modelSlug}_${form.year}`;
+  // The id is derived from the form, so the mutation has to be created after it
+  // -- usePublishTemplate('') would PUT to /api/templates/ and 404.
+  const publish = usePublishTemplate(id);
+
+  const draft = useMemo<Template>(
+    () =>
+      ({
+        id,
+        deviceType: 'vehicle',
+        manufacturer: { slug: form.makeSlug, name: form.manufacturerName },
+        model: form.modelName,
+        year: Number(form.year),
+        attributes: {},
+        trims: [{ name: form.trimName, attributes: {} }],
+      }) as Template,
+    [id, form],
+  );
+
+  const field = (key: keyof typeof form, label: string, placeholder: string) => (
+    <label key={key} className="flex flex-col gap-1">
+      <span className="text-xs uppercase tracking-wide text-white/50">{label}</span>
+      <input
+        aria-label={label}
+        value={form[key]}
+        placeholder={placeholder}
+        onChange={(e) => setForm({ ...form, [key]: e.target.value })}
+        className="h-10 rounded-md bg-dark-grey-950 px-3 text-white placeholder:text-white/25"
+      />
+    </label>
+  );
+
+  const onCreate = async () => {
+    setExists(false);
+    const found = validateDraft(draft, EMPTY_VOCAB);
+    if (found.length > 0) {
+      setErrors(found);
+      return;
+    }
+    setErrors([]);
+    try {
+      // version null -> the route sends If-None-Match: *, so a template that
+      // already exists comes back as a conflict rather than a silent overwrite.
+      await publish.mutateAsync({ payload: toPayload(draft), version: null });
+      router.push(`/templates/${id}`);
+    } catch (err) {
+      const failure = err as PublishFailure;
+      if (failure.status === 409) setExists(true);
+      else
+        setErrors(
+          failure.errors ?? [failure.message ?? 'Could not create this template'],
+        );
+    }
+  };
+
+  return (
+    <div className="flex flex-col gap-6">
+      <h1 className="text-white">New template</h1>
+      <p className="text-white/50">
+        A model-year and the trims it shipped in. Creating one publishes immediately and
+        is attributed to you — nothing points at it yet, so nothing can be re-described.
+      </p>
+
+      <div className="grid gap-3 md:grid-cols-3">
+        {field('makeSlug', 'Make slug', 'ineos')}
+        {field('modelSlug', 'Model slug', 'grenadier')}
+        {field('year', 'Year', '2024')}
+        {field('manufacturerName', 'Manufacturer name', 'INEOS')}
+        {field('modelName', 'Model name', 'Grenadier')}
+        {field('trimName', 'First trim', 'Trialmaster')}
+      </div>
+
+      <p className="font-mono text-white/70" data-testid="derived-id">
+        {id}
+      </p>
+
+      {errors.length > 0 && (
+        <ul className="flex flex-col gap-1 rounded-xl border border-red-400/40 bg-surface-raised p-4">
+          {errors.map((e) => (
+            <li key={e} className="text-red-400">
+              {e}
+            </li>
+          ))}
+        </ul>
+      )}
+
+      {exists && (
+        <div
+          role="alert"
+          className="flex items-center gap-3 rounded-xl border border-red-400/40 bg-surface-raised p-4"
+        >
+          <span className="text-red-400">A template with this id already exists.</span>
+          <Link href={`/templates/${id}`} className="button">
+            Open it
+          </Link>
+        </div>
+      )}
+
+      <div>
+        <Button onClick={onCreate} loading={publish.isPending}>
+          Create template
+        </Button>
+      </div>
+    </div>
+  );
+};
diff --git a/src/app/templates/new/components/View/index.ts b/src/app/templates/new/components/View/index.ts
new file mode 100644
index 00000000..450cf3c6
--- /dev/null
+++ b/src/app/templates/new/components/View/index.ts
@@ -0,0 +1 @@
+export * from './View';
diff --git a/src/app/templates/new/page.tsx b/src/app/templates/new/page.tsx
new file mode 100644
index 00000000..9b36ca23
--- /dev/null
+++ b/src/app/templates/new/page.tsx
@@ -0,0 +1,21 @@
+'use client';
+
+import React, { Suspense, type FC } from 'react';
+import { useSearchParams } from 'next/navigation';
+
+import { NewTemplateView } from './components/View';
+
+// useSearchParams must sit inside a Suspense boundary, and keeping it out of the
+// view leaves the view a pure function of its props for the tests.
+const PresetView: FC = () => {
+  const search = useSearchParams();
+  return <NewTemplateView presetId={search.get('id') ?? undefined} />;
+};
+
+const NewTemplatePage: FC = () => (
+  <Suspense fallback={<div>Loading...</div>}>
+    <PresetView />
+  </Suspense>
+);
+
+export default NewTemplatePage;
diff --git a/src/app/templates/page.tsx b/src/app/templates/page.tsx
new file mode 100644
index 00000000..a10d2081
--- /dev/null
+++ b/src/app/templates/page.tsx
@@ -0,0 +1,13 @@
+'use client';
+
+import React, { Suspense, type FC } from 'react';
+
+import { TemplatesPage as View } from './templatesPage/View';
+
+const TemplatesPage: FC = () => (
+  <Suspense fallback={<div>Loading...</div>}>
+    <View />
+  </Suspense>
+);
+
+export default TemplatesPage;
diff --git a/src/app/templates/templatesPage/Header/Header.tsx b/src/app/templates/templatesPage/Header/Header.tsx
new file mode 100644
index 00000000..e87146ee
--- /dev/null
+++ b/src/app/templates/templatesPage/Header/Header.tsx
@@ -0,0 +1,11 @@
+import React from 'react';
+
+export const Header = () => {
+  return (
+    <div className="flex flex-row gap-1 pb-2 border-b-cta-default border-b">
+      <p className={'text-base text-text-secondary font-medium'}>
+        One model-year, and the trims it shipped in
+      </p>
+    </div>
+  );
+};
diff --git a/src/app/templates/templatesPage/Header/index.ts b/src/app/templates/templatesPage/Header/index.ts
new file mode 100644
index 00000000..266dec8a
--- /dev/null
+++ b/src/app/templates/templatesPage/Header/index.ts
@@ -0,0 +1 @@
+export * from './Header';
diff --git a/src/app/templates/templatesPage/View/View.tsx b/src/app/templates/templatesPage/View/View.tsx
new file mode 100644
index 00000000..e0aa4286
--- /dev/null
+++ b/src/app/templates/templatesPage/View/View.tsx
@@ -0,0 +1,98 @@
+'use client';
+
+import React, { useState } from 'react';
+import Link from 'next/link';
+import { Header } from '@/app/templates/templatesPage/Header';
+import { useTemplateSearch } from '@/hooks/queries/useTemplateSearch';
+import { QueryPageWrapper } from '@/components/QueryPageWrapper';
+import { Button } from '@/components/Button';
+
+const STATUS_COPY: Record<string, { label: string; className: string; hint: string }> = {
+  'ok': { label: 'Template', className: 'text-white', hint: '' },
+  'missing': {
+    label: 'No template yet',
+    className: 'text-white/50',
+    hint: 'This model-year exists but no template has been imported for it.',
+  },
+  'invalid-id': {
+    label: 'Id cannot be a template',
+    className: 'text-red-400',
+    hint: 'This device definition id does not match the template id pattern, so it cannot be edited until the id is corrected.',
+  },
+};
+
+export const TemplatesPage = () => {
+  const [form, setForm] = useState({ make: '', model: '', year: '' });
+  const [query, setQuery] = useState(form);
+  const { data, isLoading, error } = useTemplateSearch(query);
+
+  return (
+    <div className="flex flex-col gap-6">
+      <Header />
+
+      <form
+        className="flex flex-wrap items-end gap-3"
+        onSubmit={(e) => {
+          e.preventDefault();
+          setQuery(form);
+        }}
+      >
+        {(['make', 'model', 'year'] as const).map((field) => (
+          <label key={field} className="flex flex-col gap-1 text-white/50">
+            <span className="text-xs uppercase tracking-wide">{field}</span>
+            <input
+              value={form[field]}
+              onChange={(e) => setForm({ ...form, [field]: e.target.value })}
+              placeholder={
+                field === 'make' ? 'Toyota' : field === 'model' ? 'Camry' : '2020'
+              }
+              className="h-10 rounded-full bg-dark-grey-950 px-4 text-white placeholder:text-white/25"
+            />
+          </label>
+        ))}
+        <Button type="submit">Search</Button>
+      </form>
+
+      <QueryPageWrapper
+        loading={isLoading}
+        error={error ?? undefined}
+        customErrorMessage="There was a problem searching device definitions"
+      >
+        {data && !data.manufacturer && (
+          <p className="text-white/50">No manufacturer matched that name or slug.</p>
+        )}
+        <ul className="flex flex-col divide-y divide-cta-default rounded-xl border border-cta-default bg-surface-default">
+          {(data?.results ?? []).map((r) => (
+            <li key={r.id} className="flex items-center justify-between gap-4 px-4 py-3">
+              <div className="flex flex-col">
+                <span className="font-mono text-white">{r.id}</span>
+                <span className={`text-xs ${STATUS_COPY[r.status].className}`}>
+                  {STATUS_COPY[r.status].label}
+                  {r.status === 'ok' &&
+                    ` · v${r.version} · ${r.trims} trim${r.trims === 1 ? '' : 's'}`}
+                </span>
+                {STATUS_COPY[r.status].hint && (
+                  <span className="pt-1 text-xs text-white/40">
+                    {STATUS_COPY[r.status].hint}
+                  </span>
+                )}
+              </div>
+              {r.status !== 'invalid-id' && (
+                <Link
+                  href={
+                    r.status === 'ok'
+                      ? `/templates/${r.id}`
+                      : `/templates/new?id=${encodeURIComponent(r.id)}`
+                  }
+                  className="button"
+                >
+                  {r.status === 'ok' ? 'Open' : 'Create'}
+                </Link>
+              )}
+            </li>
+          ))}
+        </ul>
+      </QueryPageWrapper>
+    </div>
+  );
+};
diff --git a/src/app/templates/templatesPage/View/index.ts b/src/app/templates/templatesPage/View/index.ts
new file mode 100644
index 00000000..450cf3c6
--- /dev/null
+++ b/src/app/templates/templatesPage/View/index.ts
@@ -0,0 +1 @@
+export * from './View';
diff --git a/src/components/TemplateEditor/DivergenceRail/DivergenceRail.tsx b/src/components/TemplateEditor/DivergenceRail/DivergenceRail.tsx
new file mode 100644
index 00000000..38f272ac
--- /dev/null
+++ b/src/components/TemplateEditor/DivergenceRail/DivergenceRail.tsx
@@ -0,0 +1,40 @@
+import React, { type FC } from 'react';
+import type { GridRow } from '@/utils/templateGrid';
+
+interface Props {
+  row: GridRow;
+  readOnly?: boolean;
+  onLift: (name: string) => void;
+}
+
+/**
+ * How many distinct values this attribute holds across the trims. At 1 with the
+ * attribute still living on the trims, the correct modelling action under the
+ * template-or-trim rule is to move it up — so that is what the rail offers,
+ * rather than a generic edit affordance.
+ */
+export const DivergenceRail: FC<Props> = ({ row, readOnly, onLift }) => {
+  if (row.scope === 'absent') return <span className="text-white/25">·</span>;
+  if (row.scope === 'shared') return <span className="text-white/40">shared</span>;
+
+  return (
+    <span className="flex items-center gap-2">
+      <span
+        className={
+          row.distinct > 1 ? 'tabular-nums text-white' : 'tabular-nums text-white/50'
+        }
+      >
+        {row.distinct}
+      </span>
+      {row.canLift && !readOnly && (
+        <button
+          type="button"
+          onClick={() => onLift(row.def.name)}
+          className="rounded-full border border-cta-default px-2 py-0.5 text-xs text-white/70 hover:border-white hover:text-white"
+        >
+          Move to shared
+        </button>
+      )}
+    </span>
+  );
+};
diff --git a/src/components/TemplateEditor/DivergenceRail/index.ts b/src/components/TemplateEditor/DivergenceRail/index.ts
new file mode 100644
index 00000000..e15a5212
--- /dev/null
+++ b/src/components/TemplateEditor/DivergenceRail/index.ts
@@ -0,0 +1 @@
+export * from './DivergenceRail';
diff --git a/src/components/TemplateEditor/EntitlementBanner/EntitlementBanner.tsx b/src/components/TemplateEditor/EntitlementBanner/EntitlementBanner.tsx
new file mode 100644
index 00000000..c9f2ef09
--- /dev/null
+++ b/src/components/TemplateEditor/EntitlementBanner/EntitlementBanner.tsx
@@ -0,0 +1,37 @@
+import React, { type FC } from 'react';
+import classnames from 'classnames';
+// `import type`, not a value import: templateEntitlement reaches next/headers
+// through getUserByToken, and pulling it into a client component would break the
+// build. The type is erased; the module is never bundled.
+import type { Entitlement } from '@/services/templateEntitlement';
+
+const TITLES: Record<Entitlement['kind'], string> = {
+  'create': 'New template',
+  'author': 'You can publish this',
+  'manufacturer': 'You hold this Manufacturer NFT',
+  'curator': 'Curator',
+  'proposal-required': 'Read only',
+};
+
+export const EntitlementBanner: FC<{ entitlement: Entitlement }> = ({ entitlement }) => (
+  <div
+    role="status"
+    className={classnames(
+      'flex flex-col gap-1 rounded-xl border p-4',
+      entitlement.canPublish
+        ? 'border-cta-default bg-surface-default text-white/70'
+        : 'border-red-400/40 bg-surface-raised text-white/70',
+    )}
+  >
+    <span className={entitlement.canPublish ? 'text-white' : 'text-red-400'}>
+      {TITLES[entitlement.kind]}
+      {!entitlement.canPublish && ' — read only'}
+    </span>
+    <span>{entitlement.reason}</span>
+    {!entitlement.canSetHardwareTemplateId && (
+      <span className="text-white/40">
+        hardwareTemplateId decides what hardware ships and is set by DIMO only.
+      </span>
+    )}
+  </div>
+);
diff --git a/src/components/TemplateEditor/EntitlementBanner/index.ts b/src/components/TemplateEditor/EntitlementBanner/index.ts
new file mode 100644
index 00000000..6e678b5c
--- /dev/null
+++ b/src/components/TemplateEditor/EntitlementBanner/index.ts
@@ -0,0 +1 @@
+export * from './EntitlementBanner';
diff --git a/src/components/TemplateEditor/NormalisationPanel/NormalisationPanel.tsx b/src/components/TemplateEditor/NormalisationPanel/NormalisationPanel.tsx
new file mode 100644
index 00000000..3c76d64d
--- /dev/null
+++ b/src/components/TemplateEditor/NormalisationPanel/NormalisationPanel.tsx
@@ -0,0 +1,39 @@
+import React, { type FC } from 'react';
+import type { Normalisation } from '@/utils/templateCoerce';
+
+interface Props {
+  notes: Normalisation[];
+  onDismiss: () => void;
+}
+
+/**
+ * Everything the editor stored that is not literally what was typed. A value
+ * that changes without a report is the failure mode this project keeps
+ * producing; this is where it is refused. Absent when there is nothing to say.
+ */
+export const NormalisationPanel: FC<Props> = ({ notes, onDismiss }) => {
+  if (notes.length === 0) return null;
+  return (
+    <section className="rounded-xl border border-cta-default bg-surface-raised p-4">
+      <div className="flex items-start justify-between gap-4">
+        <h2 className="text-white">What the editor changed that you did not type</h2>
+        <button
+          type="button"
+          onClick={onDismiss}
+          className="text-xs text-white/50 hover:text-white"
+        >
+          Dismiss
+        </button>
+      </div>
+      <ul className="flex flex-col gap-1 pt-2">
+        {notes.map((n, i) => (
+          <li key={`${n.attribute}-${i}`} className="text-white/70">
+            <span className="font-mono text-white/50">{n.attribute}</span>
+            <span className="px-2 text-white/25">·</span>
+            {n.reason}
+          </li>
+        ))}
+      </ul>
+    </section>
+  );
+};
diff --git a/src/components/TemplateEditor/NormalisationPanel/index.ts b/src/components/TemplateEditor/NormalisationPanel/index.ts
new file mode 100644
index 00000000..f4e08c37
--- /dev/null
+++ b/src/components/TemplateEditor/NormalisationPanel/index.ts
@@ -0,0 +1 @@
+export * from './NormalisationPanel';
diff --git a/src/components/TemplateEditor/TrimGrid/TemplateCell.tsx b/src/components/TemplateEditor/TrimGrid/TemplateCell.tsx
new file mode 100644
index 00000000..fabe9734
--- /dev/null
+++ b/src/components/TemplateEditor/TrimGrid/TemplateCell.tsx
@@ -0,0 +1,98 @@
+import React, { useState, type FC } from 'react';
+import classnames from 'classnames';
+import type { AttributeDef, AttributeValue } from '@/types/template';
+import { coerce, type Normalisation } from '@/utils/templateCoerce';
+
+interface Props {
+  def: AttributeDef;
+  value: AttributeValue | undefined;
+  where: string;
+  emphasised: boolean;
+  readOnly?: boolean;
+  testId: string;
+  onSet: (value: AttributeValue) => void;
+  onClear: () => void;
+  onNormalise: (note: Normalisation) => void;
+}
+
+const NOT_SET = '—';
+
+export const TemplateCell: FC<Props> = ({
+  def,
+  value,
+  where,
+  emphasised,
+  readOnly,
+  testId,
+  onSet,
+  onClear,
+  onNormalise,
+}) => {
+  const [draft, setDraft] = useState<string>(value === undefined ? '' : String(value));
+  const [error, setError] = useState<string | null>(null);
+
+  // Agreement recedes, difference advances. There is no light font weight in
+  // this design system, so emphasis rides entirely on opacity.
+  const tone =
+    value === undefined ? 'text-white/25' : emphasised ? 'text-white' : 'text-white/40';
+
+  const commit = (raw: string) => {
+    const result = coerce(def, raw, where);
+    if (result.kind === 'error') {
+      setError(result.message);
+      return;
+    }
+    setError(null);
+    if (result.note) onNormalise(result.note);
+    if (result.kind === 'clear') {
+      setDraft('');
+      onClear();
+      return;
+    }
+    setDraft(String(result.value));
+    onSet(result.value);
+  };
+
+  if (readOnly) {
+    return (
+      <div data-testid={testId} className={classnames('px-3 py-2', tone)}>
+        {value === undefined ? NOT_SET : String(value)}
+      </div>
+    );
+  }
+
+  return (
+    <div data-testid={testId} className={classnames('px-2 py-1.5', tone)}>
+      {def.type === 'enum' || def.type === 'boolean' ? (
+        <select
+          aria-label={`${where} ${def.label}`}
+          value={draft}
+          onChange={(e) => {
+            setDraft(e.target.value);
+            commit(e.target.value);
+          }}
+          className={classnames('w-full rounded-md bg-dark-grey-950 px-2 py-1', tone)}
+        >
+          <option value="">{NOT_SET}</option>
+          {(def.type === 'boolean' ? ['true', 'false'] : (def.options ?? [])).map((o) => (
+            <option key={o} value={o}>
+              {o}
+            </option>
+          ))}
+        </select>
+      ) : (
+        <input
+          type="text"
+          inputMode={def.type === 'string' ? 'text' : 'decimal'}
+          aria-label={`${where} ${def.label}`}
+          placeholder={NOT_SET}
+          value={draft}
+          onChange={(e) => setDraft(e.target.value)}
+          onBlur={(e) => commit(e.target.value)}
+          className={classnames('w-full rounded-md bg-dark-grey-950 px-2 py-1', tone)}
+        />
+      )}
+      {error && <p className="pt-1 text-xs text-red-400">{error}</p>}
+    </div>
+  );
+};
diff --git a/src/components/TemplateEditor/TrimGrid/TrimGrid.tsx b/src/components/TemplateEditor/TrimGrid/TrimGrid.tsx
new file mode 100644
index 00000000..3c90e2dd
--- /dev/null
+++ b/src/components/TemplateEditor/TrimGrid/TrimGrid.tsx
@@ -0,0 +1,123 @@
+import React, { type FC } from 'react';
+import type { DeviceType, Template } from '@/types/template';
+import type { Normalisation } from '@/utils/templateCoerce';
+import {
+  buildGrid,
+  clearShared,
+  clearTrimValue,
+  liftToShared,
+  setShared,
+  setTrimValue,
+} from '@/utils/templateGrid';
+import { DivergenceRail } from '@/components/TemplateEditor/DivergenceRail';
+import { TemplateCell } from './TemplateCell';
+import { TrimHeader } from './TrimHeader';
+
+export interface TrimGridProps {
+  template: Template;
+  vocab: DeviceType;
+  readOnly?: boolean;
+  onChange: (next: Template) => void;
+  onNormalise: (note: Normalisation) => void;
+}
+
+export const TrimGrid: FC<TrimGridProps> = ({
+  template,
+  vocab,
+  readOnly,
+  onChange,
+  onNormalise,
+}) => {
+  const grid = buildGrid(template, vocab);
+  const multiTrim = template.trims.length > 1;
+
+  return (
+    <div className="overflow-x-auto rounded-xl border border-cta-default bg-surface-default">
+      <table className="w-full border-collapse text-sm">
+        <thead>
+          <tr className="bg-surface-sunken">
+            <th
+              scope="col"
+              className="sticky left-0 z-10 bg-surface-sunken px-3 py-2 text-left text-white/50"
+            >
+              Attribute
+            </th>
+            <th scope="col" className="px-3 py-2 text-left text-white/50">
+              Values
+            </th>
+            {template.trims.map((trim, i) => (
+              <th
+                key={`${trim.name}-${i}`}
+                scope="col"
+                className="border-l border-cta-default align-top"
+              >
+                <TrimHeader trim={trim} multiTrim={multiTrim} />
+              </th>
+            ))}
+          </tr>
+        </thead>
+        <tbody>
+          {grid.rows.map((row) => (
+            <tr key={row.def.name} className="border-t border-cta-default">
+              <th
+                scope="row"
+                className="sticky left-0 z-10 bg-surface-default px-3 py-2 text-left font-normal text-white/70"
+              >
+                {row.def.label}
+                {row.def.unit && (
+                  <span className="pl-1 text-white/40">({row.def.unit})</span>
+                )}
+              </th>
+              <td data-testid={`rail-${row.def.name}`} className="px-3 py-2">
+                <DivergenceRail
+                  row={row}
+                  readOnly={readOnly}
+                  onLift={(n) => onChange(liftToShared(template, n))}
+                />
+              </td>
+              {row.scope === 'trim' ? (
+                template.trims.map((trim, i) => (
+                  <td
+                    key={`${trim.name}-${i}`}
+                    className="border-l border-cta-default align-top"
+                  >
+                    <TemplateCell
+                      def={row.def}
+                      value={row.cells[i]}
+                      where={`trim ${trim.name || '?'}`}
+                      emphasised={row.distinct > 1}
+                      readOnly={readOnly}
+                      testId={`cell-${row.def.name}-${i}`}
+                      onSet={(v) => onChange(setTrimValue(template, i, row.def.name, v))}
+                      onClear={() => onChange(clearTrimValue(template, i, row.def.name))}
+                      onNormalise={onNormalise}
+                    />
+                  </td>
+                ))
+              ) : (
+                // One value, stated once, spanning every trim -- the visual form
+                // of "this is true of the whole model-year".
+                <td
+                  colSpan={template.trims.length}
+                  className="border-l border-cta-default align-top"
+                >
+                  <TemplateCell
+                    def={row.def}
+                    value={row.shared}
+                    where="template"
+                    emphasised={false}
+                    readOnly={readOnly}
+                    testId={`shared-${row.def.name}`}
+                    onSet={(v) => onChange(setShared(template, row.def.name, v))}
+                    onClear={() => onChange(clearShared(template, row.def.name))}
+                    onNormalise={onNormalise}
+                  />
+                </td>
+              )}
+            </tr>
+          ))}
+        </tbody>
+      </table>
+    </div>
+  );
+};
diff --git a/src/components/TemplateEditor/TrimGrid/TrimHeader.tsx b/src/components/TemplateEditor/TrimGrid/TrimHeader.tsx
new file mode 100644
index 00000000..c720a4c5
--- /dev/null
+++ b/src/components/TemplateEditor/TrimGrid/TrimHeader.tsx
@@ -0,0 +1,34 @@
+import React, { type FC } from 'react';
+import type { Trim } from '@/types/template';
+import { hasEffectiveSelector } from '@/utils/templateGrid';
+
+interface Props {
+  trim: Trim;
+  multiTrim: boolean;
+}
+
+/**
+ * The model keys trims on manufacturerCode, so the code reads as an identifier
+ * and gets mono. A trim without an effective selector on a multi-trim template
+ * makes every decode for the model-year ambiguous; the worker refuses it, and
+ * showing that here is the difference between a validation state and a
+ * discovery at save.
+ */
+export const TrimHeader: FC<Props> = ({ trim, multiTrim }) => {
+  const code = trim.selectors?.manufacturerCode?.find((c) => c.trim().length > 0);
+  const style = trim.selectors?.styleName?.find((s) => s.trim().length > 0);
+  const missing = multiTrim && !hasEffectiveSelector(trim.selectors);
+
+  return (
+    <div className="flex min-w-[9rem] flex-col gap-0.5 px-3 py-2 text-left">
+      <span className="text-white">{trim.name}</span>
+      {missing ? (
+        <span className="font-mono text-xs text-red-400">no selector</span>
+      ) : (
+        <span className="font-mono text-xs text-white/50">
+          {code ?? style ?? trim.selectors?.vinPattern}
+        </span>
+      )}
+    </div>
+  );
+};
diff --git a/src/components/TemplateEditor/TrimGrid/index.ts b/src/components/TemplateEditor/TrimGrid/index.ts
new file mode 100644
index 00000000..23e20da5
--- /dev/null
+++ b/src/components/TemplateEditor/TrimGrid/index.ts
@@ -0,0 +1 @@
+export * from './TrimGrid';
diff --git a/src/components/TemplateEditor/TrimSelectorEditor/TrimSelectorEditor.tsx b/src/components/TemplateEditor/TrimSelectorEditor/TrimSelectorEditor.tsx
new file mode 100644
index 00000000..be083017
--- /dev/null
+++ b/src/components/TemplateEditor/TrimSelectorEditor/TrimSelectorEditor.tsx
@@ -0,0 +1,107 @@
+import React, { type FC } from 'react';
+import type { Template, TrimSelectors } from '@/types/template';
+import {
+  hasEffectiveSelector,
+  removeTrim,
+  renameTrim,
+  setSelectors,
+} from '@/utils/templateGrid';
+
+interface Props {
+  template: Template;
+  trimIndex: number;
+  readOnly?: boolean;
+  onChange: (next: Template) => void;
+}
+
+const toList = (raw: string) =>
+  raw
+    .split(',')
+    .map((s) => s.trim())
+    .filter((s) => s.length > 0);
+const fromList = (values?: string[]) => (values ?? []).join(', ');
+
+export const TrimSelectorEditor: FC<Props> = ({
+  template,
+  trimIndex,
+  readOnly,
+  onChange,
+}) => {
+  const trim = template.trims[trimIndex];
+  const multiTrim = template.trims.length > 1;
+  const missing = multiTrim && !hasEffectiveSelector(trim.selectors);
+
+  const update = (patch: Partial<TrimSelectors>) =>
+    onChange(setSelectors(template, trimIndex, { ...trim.selectors, ...patch }));
+
+  const field = (
+    label: string,
+    value: string,
+    onValue: (raw: string) => void,
+    placeholder: string,
+  ) => (
+    <label className="flex flex-col gap-1">
+      <span className="text-xs uppercase tracking-wide text-white/50">{label}</span>
+      <input
+        aria-label={label}
+        value={value}
+        readOnly={readOnly}
+        placeholder={placeholder}
+        onChange={(e) => onValue(e.target.value)}
+        className="h-10 rounded-md bg-dark-grey-950 px-3 text-white placeholder:text-white/25"
+      />
+    </label>
+  );
+
+  return (
+    <section className="flex flex-col gap-3 rounded-xl border border-cta-default bg-surface-default p-4">
+      <div className="flex items-center justify-between gap-4">
+        <input
+          aria-label="Trim name"
+          value={trim.name}
+          readOnly={readOnly}
+          onChange={(e) => onChange(renameTrim(template, trimIndex, e.target.value))}
+          className="h-10 flex-1 rounded-md bg-dark-grey-950 px-3 text-white"
+        />
+        {!readOnly && multiTrim && (
+          <button
+            type="button"
+            onClick={() => onChange(removeTrim(template, trimIndex))}
+            className="rounded-full border border-cta-default px-3 py-1 text-xs text-white/70 hover:border-white hover:text-white"
+          >
+            Remove trim
+          </button>
+        )}
+      </div>
+
+      <div className="grid gap-3 md:grid-cols-3">
+        {field(
+          'Manufacturer code',
+          fromList(trim.selectors?.manufacturerCode),
+          (raw) => update({ manufacturerCode: toList(raw) }),
+          '2532, 2546',
+        )}
+        {field(
+          'Style name',
+          fromList(trim.selectors?.styleName),
+          (raw) => update({ styleName: toList(raw) }),
+          'Hybrid LE',
+        )}
+        {field(
+          'VIN pattern',
+          trim.selectors?.vinPattern ?? '',
+          (raw) => update({ vinPattern: raw }),
+          '^4T1B11HK.*$',
+        )}
+      </div>
+
+      {missing && (
+        <p role="alert" className="text-red-400">
+          A template with more than one trim cannot have a selector-less trim: it would
+          match every signal and make every decode for this model-year ambiguous. Give
+          this trim a manufacturer code, a style name or a VIN pattern.
+        </p>
+      )}
+    </section>
+  );
+};
diff --git a/src/components/TemplateEditor/TrimSelectorEditor/index.ts b/src/components/TemplateEditor/TrimSelectorEditor/index.ts
new file mode 100644
index 00000000..a4a3a1cf
--- /dev/null
+++ b/src/components/TemplateEditor/TrimSelectorEditor/index.ts
@@ -0,0 +1 @@
+export * from './TrimSelectorEditor';
diff --git a/src/components/TemplateEditor/__tests__/TrimGrid.test.tsx b/src/components/TemplateEditor/__tests__/TrimGrid.test.tsx
new file mode 100644
index 00000000..ec897e7d
--- /dev/null
+++ b/src/components/TemplateEditor/__tests__/TrimGrid.test.tsx
@@ -0,0 +1,190 @@
+import { render, screen, fireEvent, within } from '@testing-library/react';
+import camry from '@/utils/__fixtures__/toyota_camry_2020.json';
+import { vehicleVocab } from '@/utils/__fixtures__/vehicleVocab';
+import { TrimGrid } from '@/components/TemplateEditor/TrimGrid';
+import type { Template } from '@/types/template';
+
+const t = camry as unknown as Template;
+const noop = () => {};
+
+const renderGrid = (props: Partial<React.ComponentProps<typeof TrimGrid>> = {}) =>
+  render(
+    <TrimGrid
+      template={t}
+      vocab={vehicleVocab}
+      onChange={noop}
+      onNormalise={noop}
+      {...props}
+    />,
+  );
+
+describe('TrimGrid', () => {
+  it('gives every trim a column and every vocabulary attribute a row', () => {
+    renderGrid();
+    // Compared as a set, not one getByRole per name: the Camry ships LE, XLE
+    // and Hybrid LE, so a name regex matches three columns.
+    const headers = screen.getAllByRole('columnheader').map((h) => h.textContent);
+    expect(headers.slice(0, 2)).toEqual(['Attribute', 'Values']);
+    expect(headers.slice(2)).toHaveLength(t.trims.length);
+    t.trims.forEach((trim, i) => expect(headers[i + 2]).toContain(trim.name));
+
+    const rows = screen.getAllByRole('rowheader').map((h) => h.textContent);
+    expect(rows).toHaveLength(vehicleVocab.attributes.length);
+    vehicleVocab.attributes.forEach((a, i) => expect(rows[i]).toContain(a.label));
+  });
+
+  it('mutes agreement and advances difference', () => {
+    renderGrid();
+    // powertrain_type differs across the Camry's ten trims: full contrast.
+    const diverging = screen.getByTestId('cell-powertrain_type-0');
+    expect(diverging.className).toContain('text-white');
+    expect(diverging.className).not.toContain('text-white/');
+    // number_of_doors is shared by every trim: muted.
+    expect(screen.getByTestId('shared-number_of_doors').className).toContain(
+      'text-white/40',
+    );
+  });
+
+  it('shows an em dash, not an empty cell, where nothing is set', () => {
+    renderGrid({ readOnly: true });
+    const cell = screen.getByTestId('shared-emissions_standard');
+    expect(cell).toHaveTextContent('—');
+    expect(cell.className).toContain('text-white/25');
+  });
+
+  it('reads the divergence count off the rail, and offers no lift while trims disagree', () => {
+    renderGrid();
+    expect(screen.getByTestId('rail-powertrain_type')).toHaveTextContent('2');
+    expect(
+      within(screen.getByTestId('rail-powertrain_type')).queryByRole('button'),
+    ).toBeNull();
+  });
+
+  it('offers Move to shared once every trim agrees, and lifts on click', () => {
+    const onChange = jest.fn();
+    const agreed = {
+      ...t,
+      attributes: {},
+      trims: t.trims.map((trim) => ({
+        ...trim,
+        attributes: { ...trim.attributes, number_of_doors: 4 },
+      })),
+    } as Template;
+    render(
+      <TrimGrid
+        template={agreed}
+        vocab={vehicleVocab}
+        onChange={onChange}
+        onNormalise={noop}
+      />,
+    );
+    fireEvent.click(
+      within(screen.getByTestId('rail-number_of_doors')).getByRole('button', {
+        name: /move to shared/i,
+      }),
+    );
+    expect(onChange).toHaveBeenCalledWith(
+      expect.objectContaining({
+        attributes: expect.objectContaining({ number_of_doors: 4 }),
+      }),
+    );
+  });
+
+  it('marks a trim with no effective selector, which is gate 4', () => {
+    const broken = {
+      ...t,
+      trims: [
+        ...t.trims,
+        { name: 'XLE V6', attributes: {}, selectors: { manufacturerCode: [''] } },
+      ],
+    } as Template;
+    render(
+      <TrimGrid
+        template={broken}
+        vocab={vehicleVocab}
+        onChange={noop}
+        onNormalise={noop}
+      />,
+    );
+    const header = screen.getByRole('columnheader', { name: /XLE V6/ });
+    expect(header).toHaveTextContent('no selector');
+    expect(within(header).getByText('no selector').className).toContain('text-red-400');
+  });
+
+  it('offers exactly the vocabulary options for an enum, plus not set', () => {
+    renderGrid();
+    const select = within(screen.getByTestId('cell-powertrain_type-0')).getByRole(
+      'combobox',
+    );
+    expect(
+      within(select)
+        .getAllByRole('option')
+        .map((o) => o.textContent),
+    ).toEqual(['—', 'ICE', 'HEV', 'PHEV', 'BEV', 'FCEV']);
+  });
+
+  it('types a value, reports the reparse, and never stores the text', () => {
+    const onChange = jest.fn();
+    const onNormalise = jest.fn();
+    render(
+      <TrimGrid
+        template={t}
+        vocab={vehicleVocab}
+        onChange={onChange}
+        onNormalise={onNormalise}
+      />,
+    );
+    const input = within(screen.getByTestId('cell-fuel_tank_capacity_gal-0')).getByRole(
+      'textbox',
+    );
+    fireEvent.change(input, { target: { value: '15.800000' } });
+    fireEvent.blur(input);
+    expect(onChange.mock.calls[0][0].trims[0].attributes.fuel_tank_capacity_gal).toBe(
+      15.8,
+    );
+    expect(onNormalise).toHaveBeenCalledWith(
+      expect.objectContaining({ attribute: 'fuel_tank_capacity_gal', to: 15.8 }),
+    );
+  });
+
+  it('clearing a cell removes the attribute and says so', () => {
+    const onChange = jest.fn();
+    const onNormalise = jest.fn();
+    render(
+      <TrimGrid
+        template={t}
+        vocab={vehicleVocab}
+        onChange={onChange}
+        onNormalise={onNormalise}
+      />,
+    );
+    const input = within(screen.getByTestId('cell-mpg_city-0')).getByRole('textbox');
+    fireEvent.change(input, { target: { value: '' } });
+    fireEvent.blur(input);
+    expect('mpg_city' in onChange.mock.calls[0][0].trims[0].attributes).toBe(false);
+    expect(onNormalise).toHaveBeenCalledWith(expect.objectContaining({ to: null }));
+  });
+
+  it('refuses an out-of-range value in the worker words and does not change the template', () => {
+    const onChange = jest.fn();
+    render(
+      <TrimGrid
+        template={t}
+        vocab={vehicleVocab}
+        onChange={onChange}
+        onNormalise={noop}
+      />,
+    );
+    const cell = screen.getByTestId('cell-mpg_city-0');
+    fireEvent.change(within(cell).getByRole('textbox'), { target: { value: '400' } });
+    fireEvent.blur(within(cell).getByRole('textbox'));
+    expect(onChange).not.toHaveBeenCalled();
+    expect(cell).toHaveTextContent('trim LE: "mpg_city" above maximum 200');
+  });
+
+  it('renders no inputs when read only', () => {
+    renderGrid({ readOnly: true });
+    expect(screen.queryAllByRole('textbox')).toHaveLength(0);
+    expect(screen.queryAllByRole('combobox')).toHaveLength(0);
+  });
+});
diff --git a/src/components/TemplateEditor/__tests__/honestySurfaces.test.tsx b/src/components/TemplateEditor/__tests__/honestySurfaces.test.tsx
new file mode 100644
index 00000000..ccbbcba1
--- /dev/null
+++ b/src/components/TemplateEditor/__tests__/honestySurfaces.test.tsx
@@ -0,0 +1,118 @@
+import { render, screen, fireEvent } from '@testing-library/react';
+import camry from '@/utils/__fixtures__/toyota_camry_2020.json';
+import { NormalisationPanel } from '@/components/TemplateEditor/NormalisationPanel';
+import { TrimSelectorEditor } from '@/components/TemplateEditor/TrimSelectorEditor';
+import { EntitlementBanner } from '@/components/TemplateEditor/EntitlementBanner';
+import type { Template } from '@/types/template';
+
+const t = camry as unknown as Template;
+
+describe('NormalisationPanel', () => {
+  it('renders nothing when the editor changed nothing', () => {
+    const { container } = render(<NormalisationPanel notes={[]} onDismiss={() => {}} />);
+    expect(container).toBeEmptyDOMElement();
+  });
+
+  it('says what was stored instead of what was typed', () => {
+    render(
+      <NormalisationPanel
+        notes={[
+          {
+            attribute: 'fuel_tank_capacity_gal',
+            from: '15.800000',
+            to: 15.8,
+            reason: 'stored as the number 15.8, not the text "15.800000"',
+          },
+          {
+            attribute: 'mpg_city',
+            from: '',
+            to: null,
+            reason: 'cleared — the attribute is removed, not stored empty',
+          },
+        ]}
+        onDismiss={() => {}}
+      />,
+    );
+    expect(screen.getByText(/stored as the number 15.8/)).toBeInTheDocument();
+    expect(
+      screen.getByText(/the attribute is removed, not stored empty/),
+    ).toBeInTheDocument();
+  });
+});
+
+describe('TrimSelectorEditor', () => {
+  it('shows the gate 4 state for a trim with no effective selector', () => {
+    const broken = {
+      ...t,
+      trims: [
+        ...t.trims,
+        { name: 'XLE V6', attributes: {}, selectors: { vinPattern: '  ' } },
+      ],
+    } as Template;
+    render(
+      <TrimSelectorEditor
+        template={broken}
+        trimIndex={broken.trims.length - 1}
+        onChange={() => {}}
+      />,
+    );
+    expect(screen.getByRole('alert')).toHaveTextContent(
+      'A template with more than one trim cannot have a selector-less trim',
+    );
+  });
+
+  it('is quiet when the trim has a real selector', () => {
+    render(<TrimSelectorEditor template={t} trimIndex={0} onChange={() => {}} />);
+    expect(screen.queryByRole('alert')).toBeNull();
+  });
+
+  it('splits a comma separated list into manufacturer codes and drops the blanks', () => {
+    const onChange = jest.fn();
+    render(<TrimSelectorEditor template={t} trimIndex={0} onChange={onChange} />);
+    fireEvent.change(screen.getByLabelText(/manufacturer code/i), {
+      target: { value: '2532, , 2533 ' },
+    });
+    expect(onChange.mock.calls.at(-1)![0].trims[0].selectors.manufacturerCode).toEqual([
+      '2532',
+      '2533',
+    ]);
+  });
+});
+
+describe('EntitlementBanner', () => {
+  it('explains a proposal requirement and names the vehicle count', () => {
+    render(
+      <EntitlementBanner
+        entitlement={{
+          kind: 'proposal-required',
+          canPublish: false,
+          canSetHardwareTemplateId: false,
+          mintedVehicles: 4212,
+          reason: '4,212 minted vehicles resolve to this template.',
+        }}
+      />,
+    );
+    expect(screen.getByRole('status')).toHaveTextContent(
+      '4,212 minted vehicles resolve to this template.',
+    );
+    expect(screen.getByRole('status')).toHaveTextContent('read only');
+  });
+
+  it('says nothing loud when the caller may publish', () => {
+    render(
+      <EntitlementBanner
+        entitlement={{
+          kind: 'author',
+          canPublish: true,
+          canSetHardwareTemplateId: false,
+          mintedVehicles: 0,
+          reason: 'No vehicle references this template yet.',
+        }}
+      />,
+    );
+    expect(screen.getByRole('status')).toHaveTextContent(
+      'No vehicle references this template yet.',
+    );
+    expect(screen.getByRole('status').className).not.toContain('red');
+  });
+});
diff --git a/src/config/default.ts b/src/config/default.ts
index 335af9cd..6095125d 100644
--- a/src/config/default.ts
+++ b/src/config/default.ts
@@ -44,6 +44,10 @@ export const frontendUrl = 'http://localhost:3000/';
 
 export const identityApiUrl = 'https://identity-api.dev.dimo.zone/query';
 
+// definitions-worker: canonical template documents on R2, plus the schema
+// documents the editor form is driven by. See definitions-worker/wrangler.toml.
+export const definitionsWorkerUrl = 'https://definitions.dev.dimo.org';
+
 export const RAINBOW_PROJECT = {
   ID: '528803928611a7781fb6b23eaf232224',
   NAME: 'Dimo Developer Console',
diff --git a/src/config/index.ts b/src/config/index.ts
index b3843881..6b9ee58d 100644
--- a/src/config/index.ts
+++ b/src/config/index.ts
@@ -30,6 +30,7 @@ type Configuration = {
   ISSUED_TOPIC: `0x${string}`;
   CONTRACT_METHODS: Record<keyof typeof CONTRACT_METHODS, string>;
   identityApiUrl: string;
+  definitionsWorkerUrl: string;
   DIMO_ESCROW_ADDRESS: `0x${string}`;
   DIMO_SACD_ADDRESS: `0x${string}`;
   DIMO_REGISTRY_ADDRESS: `0x${string}`;
diff --git a/src/config/navigation.ts b/src/config/navigation.ts
index 599eda96..8decf5e6 100644
--- a/src/config/navigation.ts
+++ b/src/config/navigation.ts
@@ -1,4 +1,5 @@
 import {
+  CarRentalIcon,
   HomeIcon,
   IntegrationIcon,
   MonitorHeartIcon,
@@ -12,6 +13,7 @@ const APP_DETAILS_REGEX = /^\/app\/details\/[^/]+$/;
 const EXPLORER_VEHICLE_REGEX = /^\/explorer\/[^/]+$/;
 const LICENSE_DETAILS_REGEX = /^\/license\/details\/[^/]+$/;
 const LICENSED_VEHICLES_REGEX = /^\/license\/vehicles\/[^/]+$/;
+const TEMPLATE_EDIT_REGEX = /^\/templates\/[^/]+$/;
 const CREATE_WEBHOOK_REGEX = /^\/webhooks\/create\/[^/]+$/;
 const EDIT_WEBHOOK_REGEX = /^\/webhooks\/edit\/[^/]+\/[^/]+$/;
 const CREATE_CONNECTION_REGEX = /^\/connections\/create\/[^/]+$/;
@@ -28,12 +30,17 @@ export const getPageTitle = (path: string) => {
   if (EDIT_WEBHOOK_REGEX.test(path)) return 'Edit webhook';
   if (CREATE_CONNECTION_REGEX.test(path)) return 'Create a Connection';
   if (CONNECTION_DETAILS_REGEX.test(path)) return 'Connection Details';
+  // Ordered before TEMPLATE_EDIT_REGEX, which would otherwise match
+  // /templates/new and title the create page "Edit template".
+  if (path === '/templates/new') return 'New template';
+  if (TEMPLATE_EDIT_REGEX.test(path)) return 'Edit template';
 };
 
 const pageTitles: Record<string, string> = {
   '/': 'Home',
   '/app': 'Home',
   '/webhooks': 'Webhooks',
+  '/templates': 'Vehicle templates',
   '/api-status': 'API Status',
   '/connections': 'Connections',
   '/settings': 'Settings',
@@ -67,6 +74,14 @@ const baseMainMenu = [
     external: false,
     disabled: false,
   },
+  {
+    label: 'Templates',
+    icon: CarRentalIcon,
+    iconClassName: 'h-5 w-5',
+    link: '/templates',
+    external: false,
+    disabled: false,
+  },
   {
     label: 'Documentation',
     icon: SummarizeIcon,
diff --git a/src/config/preview.ts b/src/config/preview.ts
index 188c1ca9..b4d0983d 100644
--- a/src/config/preview.ts
+++ b/src/config/preview.ts
@@ -10,6 +10,8 @@ export enum CONTRACT_METHODS {
 
 export const identityApiUrl = 'https://identity-api.dev.dimo.zone/query';
 
+export const definitionsWorkerUrl = 'https://definitions.dev.dimo.org';
+
 export const DCC_ADDRESS = '0x41799E9Dc893722844E771a1C1cAf3BBc2876132'; // Connections
 
 // DIMO REGISTRY AMOY
diff --git a/src/config/production.ts b/src/config/production.ts
index d5893828..d1d5d447 100644
--- a/src/config/production.ts
+++ b/src/config/production.ts
@@ -31,6 +31,8 @@ export const CONTRACT_METHODS = {
 
 export const identityApiUrl = 'https://identity-api.dimo.zone/query';
 
+export const definitionsWorkerUrl = 'https://definitions.dimo.org';
+
 export const DIMO_ESCROW_ADDRESS = '0x69977330D192701071D9b370Ac849065A545dEA5';
 
 export const DIMO_SACD_ADDRESS = '0x3c152B5d96769661008Ff404224d6530FCAC766d';
diff --git a/src/hooks/queries/useTemplate.ts b/src/hooks/queries/useTemplate.ts
new file mode 100644
index 00000000..759aed38
--- /dev/null
+++ b/src/hooks/queries/useTemplate.ts
@@ -0,0 +1,61 @@
+'use client';
+
+import { useMutation, useQuery } from '@tanstack/react-query';
+import type { DeviceType, Template, TemplatePayload } from '@/types/template';
+import type { Entitlement } from '@/services/templateEntitlement';
+
+export interface TemplateBundle {
+  template: Template | null;
+  vocabulary: DeviceType;
+  entitlement: Entitlement;
+}
+
+export interface PublishFailure {
+  status: number;
+  message?: string;
+  errors?: string[];
+  conflict?: { expected: number | null; actual: number };
+}
+
+export const useTemplate = (id: string) =>
+  useQuery<TemplateBundle>({
+    queryKey: ['template', id],
+    // The version held here is what If-Match sends. A cached one would send a
+    // stale precondition and turn a real conflict into a silent rebase.
+    staleTime: 0,
+    refetchOnWindowFocus: false,
+    queryFn: async () => {
+      const resp = await fetch(`/api/templates/${encodeURIComponent(id)}`);
+      const json = await resp.json();
+      if (!resp.ok) throw new Error(json.error ?? 'Failed to load template');
+      return json as TemplateBundle;
+    },
+  });
+
+export const usePublishTemplate = (id: string) =>
+  useMutation<
+    Template,
+    PublishFailure,
+    { payload: TemplatePayload; version: number | null }
+  >({
+    mutationFn: async ({ payload, version }) => {
+      const resp = await fetch(`/api/templates/${encodeURIComponent(id)}`, {
+        method: 'PUT',
+        headers: {
+          'Content-Type': 'application/json',
+          ...(version === null ? {} : { 'If-Match': `"${version}"` }),
+        },
+        body: JSON.stringify(payload),
+      });
+      const json = await resp.json();
+      if (!resp.ok) {
+        throw {
+          status: resp.status,
+          message: json.error,
+          errors: json.errors,
+          conflict: json.conflict,
+        } as PublishFailure;
+      }
+      return json.template as Template;
+    },
+  });
diff --git a/src/hooks/queries/useTemplateSearch.ts b/src/hooks/queries/useTemplateSearch.ts
new file mode 100644
index 00000000..8cf0dbdd
--- /dev/null
+++ b/src/hooks/queries/useTemplateSearch.ts
@@ -0,0 +1,30 @@
+'use client';
+
+import { useQuery } from '@tanstack/react-query';
+import type { SearchResult } from '@/app/api/templates/route';
+
+export interface TemplateSearch {
+  manufacturer: { name: string; tokenId: number } | null;
+  results: SearchResult[];
+}
+
+export const useTemplateSearch = (params: {
+  make: string;
+  model: string;
+  year: string;
+}) =>
+  useQuery<TemplateSearch>({
+    queryKey: ['template-search', params],
+    enabled: params.make.trim().length > 0,
+    staleTime: 30000,
+    refetchOnWindowFocus: false,
+    queryFn: async () => {
+      const qs = new URLSearchParams({ make: params.make });
+      if (params.model) qs.set('model', params.model);
+      if (params.year) qs.set('year', params.year);
+      const resp = await fetch(`/api/templates?${qs}`);
+      const json = await resp.json();
+      if (!resp.ok) throw new Error(json.error ?? 'Search failed');
+      return json as TemplateSearch;
+    },
+  });
diff --git a/src/services/definitions.ts b/src/services/definitions.ts
new file mode 100644
index 00000000..0f14119e
--- /dev/null
+++ b/src/services/definitions.ts
@@ -0,0 +1,114 @@
+import config from '@/config';
+import type { DeviceType, Template, TemplatePayload } from '@/types/template';
+
+// definitions-worker/src/index.ts MAX_DOC_BYTES. Checked here so an oversized
+// draft is reported in the editor rather than as an opaque 413 after a
+// round trip.
+const MAX_DOC_BYTES = 64 * 1024;
+
+// Gate 1: WRITE_TOKEN must never reach a browser bundle. A convention is not
+// a guarantee; this is. Any client component that imports this module fails
+// loudly in development instead of shipping the token.
+function assertServer(): void {
+  if (typeof window !== 'undefined') {
+    throw new Error(
+      'services/definitions is server-only — it holds DEFINITIONS_WRITE_TOKEN',
+    );
+  }
+}
+
+export type Precondition = { kind: 'create' } | { kind: 'update'; version: number };
+
+export type PublishResult =
+  | { ok: true; template: Template }
+  | { ok: false; kind: 'validation'; errors: string[] }
+  | { ok: false; kind: 'conflict'; expected: number | null; actual: number }
+  | { ok: false; kind: 'too-large'; bytes: number; limit: number }
+  | { ok: false; kind: 'upstream'; status: number; message: string };
+
+export async function fetchTemplate(id: string): Promise<Template | null> {
+  assertServer();
+  const resp = await fetch(`${config.definitionsWorkerUrl}/t/${encodeURIComponent(id)}`, {
+    // A template's ETag is its version, and the editor's whole conflict story
+    // depends on holding the current one. Never serve this from a cache.
+    cache: 'no-store',
+  });
+  if (resp.status === 404) return null;
+  if (!resp.ok)
+    throw new Error(`definitions-worker GET /t/${id} returned ${resp.status}`);
+  return (await resp.json()) as Template;
+}
+
+export async function fetchVocabulary(): Promise<DeviceType> {
+  assertServer();
+  const resp = await fetch(
+    `${config.definitionsWorkerUrl}/schema/device-type-vehicle.json`,
+    {
+      // Matches the worker's own max-age. The vocabulary decides which options
+      // the form offers, so it is the one document that must not go stale for
+      // longer than the validator that enforces it.
+      next: { revalidate: 300 },
+    },
+  );
+  if (!resp.ok) {
+    throw new Error(
+      `definitions-worker GET /schema/device-type-vehicle.json returned ${resp.status}`,
+    );
+  }
+  return (await resp.json()) as DeviceType;
+}
+
+export async function publishTemplate(
+  id: string,
+  payload: TemplatePayload,
+  precondition: Precondition,
+): Promise<PublishResult> {
+  assertServer();
+  const body = JSON.stringify(payload);
+  const bytes = new TextEncoder().encode(body).byteLength;
+  if (bytes > MAX_DOC_BYTES) {
+    return { ok: false, kind: 'too-large', bytes, limit: MAX_DOC_BYTES };
+  }
+
+  const headers: Record<string, string> = {
+    'Content-Type': 'application/json',
+    'Authorization': `Bearer ${process.env.DEFINITIONS_WRITE_TOKEN ?? ''}`,
+  };
+  if (precondition.kind === 'create') headers['If-None-Match'] = '*';
+  else headers['If-Match'] = `"${precondition.version}"`;
+
+  const resp = await fetch(`${config.definitionsWorkerUrl}/t/${encodeURIComponent(id)}`, {
+    method: 'PUT',
+    headers,
+    body,
+    cache: 'no-store',
+  });
+
+  if (resp.ok) return { ok: true, template: (await resp.json()) as Template };
+
+  const data = (await resp.json().catch(() => ({}))) as {
+    error?: string;
+    errors?: string[];
+    expected?: number | null;
+    actual?: number;
+  };
+
+  if (resp.status === 422)
+    return { ok: false, kind: 'validation', errors: data.errors ?? [] };
+  if (resp.status === 412) {
+    return {
+      ok: false,
+      kind: 'conflict',
+      expected: data.expected ?? null,
+      actual: data.actual ?? 0,
+    };
+  }
+  if (resp.status === 413)
+    return { ok: false, kind: 'too-large', bytes, limit: MAX_DOC_BYTES };
+  return {
+    ok: false,
+    kind: 'upstream',
+    status: resp.status,
+    message: data.error ?? `HTTP ${resp.status}`,
+  };
+}
diff --git a/src/services/templateEntitlement.ts b/src/services/templateEntitlement.ts
new file mode 100644
index 00000000..5c84a845
--- /dev/null
+++ b/src/services/templateEntitlement.ts
@@ -0,0 +1,173 @@
+import config from '@/config';
+import type { Template } from '@/types/template';
+import { getUserByToken } from '@/services/user';
+import { getUserSubOrganization } from '@/services/globalAccount';
+
+export type EntitlementKind =
+  | 'create'
+  | 'author'
+  | 'manufacturer'
+  | 'curator'
+  | 'proposal-required';
+
+export interface Entitlement {
+  kind: EntitlementKind;
+  canPublish: boolean;
+  /** DIMO only, at every tier. It decides what hardware ships. */
+  canSetHardwareTemplateId: boolean;
+  mintedVehicles: number;
+  reason: string;
+}
+
+const eq = (a?: string | null, b?: string | null) =>
+  Boolean(a && b && a.toLowerCase() === b.toLowerCase());
+
+export const curatorAddresses = (): string[] =>
+  (process.env.DIMO_CURATOR_ADDRESSES ?? '')
+    .split(',')
+    .map((a) => a.trim().toLowerCase())
+    .filter((a) => a.length > 0);
+
+/**
+ * The caller, from the session Console already has. Mirrors src/middleware.ts:
+ * the session cookie identifies a user, and the Global Account sub-organisation
+ * is what turns that user into an address. The smart contract address is used,
+ * not the Turnkey EOA: it is the address DIMO records on chain, so it is the
+ * one that can hold a Manufacturer NFT.
+ */
+export async function resolveCaller(): Promise<{
+  address: `0x${string}`;
+  email: string;
+} | null> {
+  try {
+    const user = await getUserByToken();
+    const email = user.company_email_owner ?? user.email;
+    const sub = await getUserSubOrganization(email);
+    if (!sub?.smartContractAddress) return null;
+    return { address: sub.smartContractAddress, email };
+  } catch {
+    return null;
+  }
+}
+
+async function identity<T>(
+  query: string,
+  variables: Record<string, unknown>,
+): Promise<T | null> {
+  const resp = await fetch(config.identityApiUrl, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ query, variables }),
+    cache: 'no-store',
+  });
+  if (!resp.ok) throw new Error(`identity-api returned ${resp.status}`);
+  const json = (await resp.json()) as { data?: T };
+  return json.data ?? null;
+}
+
+/** How many vehicles point at this template. This is the number that decides risk. */
+export async function countMintedVehicles(id: string): Promise<number> {
+  const data = await identity<{ vehicles: { totalCount: number } }>(
+    `query TemplateVehicles($id: String!) {
+       vehicles(filterBy: { deviceDefinitionId: $id }, first: 1) { totalCount }
+     }`,
+    { id },
+  );
+  return data?.vehicles.totalCount ?? 0;
+}
+
+export async function manufacturerOwner(
+  slug: string,
+): Promise<{ owner: string; tokenId: number } | null> {
+  const data = await identity<{
+    manufacturer: { owner: string; tokenId: number } | null;
+  }>(
+    `query TemplateManufacturer($slug: String!) {
+       manufacturer(by: { slug: $slug }) { owner tokenId }
+     }`,
+    { slug },
+  );
+  return data?.manufacturer ?? null;
+}
+
+export interface EntitlementArgs {
+  caller: string;
+  template: Template | null;
+  countMintedVehicles: (id: string) => Promise<number>;
+  manufacturerOwner: (slug: string) => Promise<{ owner: string; tokenId: number } | null>;
+  curators: string[];
+}
+
+/**
+ * The split falls where risk falls. Creating ineos_grenadier_2024 harms nobody.
+ * Editing toyota_camry_2020 silently re-describes every vehicle pointing at it.
+ */
+export async function resolveEntitlement(args: EntitlementArgs): Promise<Entitlement> {
+  const { caller, template, curators } = args;
+  const isCurator = curators.some((c) => eq(c, caller));
+
+  if (template === null) {
+    return {
+      kind: isCurator ? 'curator' : 'create',
+      canPublish: true,
+      canSetHardwareTemplateId: isCurator,
+      mintedVehicles: 0,
+      reason:
+        'This template does not exist yet, so creating it cannot re-describe anything.',
+    };
+  }
+
+  if (isCurator) {
+    return {
+      kind: 'curator',
+      canPublish: true,
+      canSetHardwareTemplateId: true,
+      mintedVehicles: await args.countMintedVehicles(template.id),
+      reason: 'You are a DIMO curator.',
+    };
+  }
+
+  const mintedVehicles = await args.countMintedVehicles(template.id);
+
+  if (mintedVehicles === 0) {
+    // An absent author is a backfill-created template, which nobody has claimed.
+    // Treating it as unowned is what keeps the open tier from being empty.
+    if (!template.author || eq(template.author, caller)) {
+      return {
+        kind: 'author',
+        canPublish: true,
+        canSetHardwareTemplateId: false,
+        mintedVehicles: 0,
+        reason: 'No vehicle references this template yet.',
+      };
+    }
+    return {
+      kind: 'proposal-required',
+      canPublish: false,
+      canSetHardwareTemplateId: false,
+      mintedVehicles: 0,
+      reason: `This template was published by ${template.author}. Editing someone else's template opens a proposal, which is not built yet.`,
+    };
+  }
+
+  const owner = await args.manufacturerOwner(template.manufacturer.slug);
+  if (owner && eq(owner.owner, caller)) {
+    return {
+      kind: 'manufacturer',
+      canPublish: true,
+      canSetHardwareTemplateId: false,
+      mintedVehicles,
+      reason: `You hold the ${template.manufacturer.name} Manufacturer NFT (token ${owner.tokenId}).`,
+    };
+  }
+
+  return {
+    kind: 'proposal-required',
+    canPublish: false,
+    canSetHardwareTemplateId: false,
+    mintedVehicles,
+    reason:
+      `${mintedVehicles.toLocaleString()} minted vehicle${mintedVehicles === 1 ? '' : 's'} resolve to this ` +
+      'template. Editing it needs a proposal a curator merges, which is not built yet.',
+  };
+}
diff --git a/src/types/generated/template.schema.json b/src/types/generated/template.schema.json
new file mode 100644
index 00000000..b2d96321
--- /dev/null
+++ b/src/types/generated/template.schema.json
@@ -0,0 +1,134 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://definitions.dimo.org/schema/template.schema.json",
+  "title": "Template",
+  "description": "A vehicle trim-configuration template: one model-year, plus the trims it shipped in. This is the object Console edits and R2 serves. Attributes true of every trim live on `attributes`; anything that differs between trims lives on that trim. A VIN decode narrows this template to exactly one trim and emits a Resolved document.",
+  "type": "object",
+  "required": [
+    "id",
+    "deviceType",
+    "manufacturer",
+    "model",
+    "year",
+    "attributes",
+    "trims",
+    "version",
+    "createdAt",
+    "updatedAt"
+  ],
+  "additionalProperties": false,
+  "properties": {
+    "id": {
+      "type": "string",
+      "pattern": "^[a-z0-9][a-z0-9._&+-]*_[a-z0-9._&+-]+_[0-9]{4}$",
+      "description": "manufacturer-slug _ model-slug _ year. The only identifier. There is no ksuid, no legacy id, and no on-chain table backing this."
+    },
+    "deviceType": {
+      "type": "string",
+      "pattern": "^[a-z0-9_]+$",
+      "description": "DeviceType id whose vocabulary this template is validated against."
+    },
+    "manufacturer": {
+      "type": "object",
+      "title": "TemplateManufacturer",
+      "description": "Denormalised into the template on purpose. Reading a template must not require a second lookup, and creating one must not require the brand to have on-chain storage provisioned first.",
+      "required": ["slug", "name"],
+      "additionalProperties": false,
+      "properties": {
+        "slug": { "type": "string", "pattern": "^[a-z0-9][a-z0-9._&+-]*$" },
+        "name": { "type": "string", "minLength": 1 },
+        "tokenId": {
+          "type": "integer",
+          "minimum": 1,
+          "description": "Manufacturer NFT, when one exists. Optional: it grants direct-edit rights, it is not a precondition for the template to exist."
+        }
+      }
+    },
+    "model": { "type": "string", "minLength": 1 },
+    "year": { "type": "integer", "minimum": 1885, "maximum": 2100 },
+    "imageURI": { "type": "string", "format": "uri" },
+    "hardwareTemplateId": {
+      "type": "string",
+      "pattern": "^[0-9]+$",
+      "default": "130",
+      "description": "Which DIMO hardware configuration this vehicle takes. NOT a vehicle attribute: it describes what our gear does with the car, not what the car is, so it sits outside `attributes` and is never validated against the DeviceType vocabulary. Template-level value is the default for every trim; a trim may override it. Today `common/utils.go:202` stamps \"130\" on every definition and exactly 3 style rows override it. Contribution-gated: an open contributor must not be able to change what hardware we ship."
+    },
+    "attributes": { "$ref": "#/$defs/attributeMap" },
+    "trims": {
+      "type": "array",
+      "minItems": 1,
+      "description": "At least one. A model-year sold in a single configuration has exactly one trim; that is still a trim, not a special case.",
+      "items": { "$ref": "#/$defs/trim" }
+    },
+    "version": {
+      "type": "integer",
+      "minimum": 1,
+      "description": "Increments on every published edit. Immutable once written: t/<id>/v/<version>.json is the permanent record."
+    },
+    "author": {
+      "type": "string",
+      "pattern": "^0x[0-9a-fA-F]{40}$",
+      "description": "Address that published this version. Every edit is attributed."
+    },
+    "createdAt": { "type": "string", "format": "date-time" },
+    "updatedAt": { "type": "string", "format": "date-time" }
+  },
+  "$defs": {
+    "trim": {
+      "type": "object",
+      "title": "Trim",
+      "required": ["name", "attributes"],
+      "additionalProperties": false,
+      "properties": {
+        "name": {
+          "type": "string",
+          "minLength": 1,
+          "description": "As the manufacturer markets it: \"XSE V6\", \"Hybrid LE\", \"Long Range AWD\"."
+        },
+        "selectors": {
+          "$ref": "#/$defs/selectors",
+          "description": "How a decoded VIN is matched to this trim. Omit on a single-trim template."
+        },
+        "hardwareTemplateId": {
+          "type": "string",
+          "pattern": "^[0-9]+$",
+          "description": "Overrides the template's value for this trim only. Omit unless this trim genuinely takes different hardware."
+        },
+        "attributes": { "$ref": "#/$defs/attributeMap" }
+      }
+    },
+    "selectors": {
+      "type": "object",
+      "title": "TrimSelectors",
+      "description": "Signals from the VIN decoder. A trim matches when every selector present matches. Most specific match wins; ties are a template defect and must be reported, not silently broken.",
+      "additionalProperties": false,
+      "properties": {
+        "manufacturerCode": {
+          "type": "array",
+          "items": { "type": "string" },
+          "description": "OEM model/option code. Already present in today's data as manufacturer_code, where it sits on the model-year record doing nothing — it is a trim key that was flattened."
+        },
+        "styleName": {
+          "type": "array",
+          "items": { "type": "string" },
+          "description": "Style string as the upstream decoder reports it. Matched case-insensitively."
+        },
+        "vinPattern": {
+          "type": "string",
+          "format": "regex",
+          "description": "Anchored regex over the 17-character VIN for OEMs that encode trim positionally."
+        }
+      }
+    },
+    "attributeMap": {
+      "type": "object",
+      "title": "AttributeMap",
+      "description": "name -> value. On the template these are the attributes shared by every trim; on a trim they are that trim's own. An attribute is either on the template or on a trim, never both. Names must exist in the DeviceType; enum values must appear in that attribute's options. An attribute that is unknown is ABSENT — never \"\" and never \"<nil>\". 6% of today's attribute rows are one of those two placeholders; this schema makes them unrepresentable.",
+      "propertyNames": { "pattern": "^[a-z0-9_]+$" },
+      "additionalProperties": {
+        "type": ["string", "number", "integer", "boolean"],
+        "description": "Typed, not stringified. fuel_tank_capacity_gal is 15.8, not \"15.800000\"."
+      }
+    }
+  }
+}
diff --git a/src/types/generated/template.ts b/src/types/generated/template.ts
new file mode 100644
index 00000000..42b06433
--- /dev/null
+++ b/src/types/generated/template.ts
@@ -0,0 +1,91 @@
+/* eslint-disable */
+// GENERATED by scripts/gen-template-types.mjs from
+// src/types/generated/template.schema.json, vendored from
+// definitions-worker/schema/template.schema.json. Do not edit.
+/**
+ * A vehicle trim-configuration template: one model-year, plus the trims it shipped in. This is the object Console edits and R2 serves. Attributes true of every trim live on `attributes`; anything that differs between trims lives on that trim. A VIN decode narrows this template to exactly one trim and emits a Resolved document.
+ */
+export interface Template {
+  /**
+   * manufacturer-slug _ model-slug _ year. The only identifier. There is no ksuid, no legacy id, and no on-chain table backing this.
+   */
+  id: string;
+  /**
+   * DeviceType id whose vocabulary this template is validated against.
+   */
+  deviceType: string;
+  manufacturer: TemplateManufacturer;
+  model: string;
+  year: number;
+  imageURI?: string;
+  /**
+   * Which DIMO hardware configuration this vehicle takes. NOT a vehicle attribute: it describes what our gear does with the car, not what the car is, so it sits outside `attributes` and is never validated against the DeviceType vocabulary. Template-level value is the default for every trim; a trim may override it. Today `common/utils.go:202` stamps "130" on every definition and exactly 3 style rows override it. Contribution-gated: an open contributor must not be able to change what hardware we ship.
+   */
+  hardwareTemplateId?: string;
+  attributes: AttributeMap;
+  /**
+   * At least one. A model-year sold in a single configuration has exactly one trim; that is still a trim, not a special case.
+   *
+   * @minItems 1
+   */
+  trims: Trim[];
+  /**
+   * Increments on every published edit. Immutable once written: t/<id>/v/<version>.json is the permanent record.
+   */
+  version: number;
+  /**
+   * Address that published this version. Every edit is attributed.
+   */
+  author?: string;
+  createdAt: string;
+  updatedAt: string;
+}
+/**
+ * Denormalised into the template on purpose. Reading a template must not require a second lookup, and creating one must not require the brand to have on-chain storage provisioned first.
+ */
+export interface TemplateManufacturer {
+  slug: string;
+  name: string;
+  /**
+   * Manufacturer NFT, when one exists. Optional: it grants direct-edit rights, it is not a precondition for the template to exist.
+   */
+  tokenId?: number;
+}
+/**
+ * name -> value. On the template these are the attributes shared by every trim; on a trim they are that trim's own. An attribute is either on the template or on a trim, never both. Names must exist in the DeviceType; enum values must appear in that attribute's options. An attribute that is unknown is ABSENT — never "" and never "<nil>". 6% of today's attribute rows are one of those two placeholders; this schema makes them unrepresentable.
+ */
+export interface AttributeMap {
+  /**
+   * Typed, not stringified. fuel_tank_capacity_gal is 15.8, not "15.800000".
+   */
+  [k: string]: string | number | boolean;
+}
+export interface Trim {
+  /**
+   * As the manufacturer markets it: "XSE V6", "Hybrid LE", "Long Range AWD".
+   */
+  name: string;
+  selectors?: TrimSelectors;
+  /**
+   * Overrides the template's value for this trim only. Omit unless this trim genuinely takes different hardware.
+   */
+  hardwareTemplateId?: string;
+  attributes: AttributeMap;
+}
+/**
+ * How a decoded VIN is matched to this trim. Omit on a single-trim template.
+ */
+export interface TrimSelectors {
+  /**
+   * OEM model/option code. Already present in today's data as manufacturer_code, where it sits on the model-year record doing nothing — it is a trim key that was flattened.
+   */
+  manufacturerCode?: string[];
+  /**
+   * Style string as the upstream decoder reports it. Matched case-insensitively.
+   */
+  styleName?: string[];
+  /**
+   * Anchored regex over the 17-character VIN for OEMs that encode trim positionally.
+   */
+  vinPattern?: string;
+}
diff --git a/src/types/template.ts b/src/types/template.ts
new file mode 100644
index 00000000..e8f955c1
--- /dev/null
+++ b/src/types/template.ts
@@ -0,0 +1,38 @@
+export type {
+  Template,
+  TemplateManufacturer,
+  Trim,
+  TrimSelectors,
+  AttributeMap,
+} from './generated/template';
+import type { Template } from './generated/template';
+
+export type AttributeValue = string | number | boolean;
+
+// The vehicle vocabulary (device-type-vehicle.json) has no schema of its own,
+// so these two are hand-written. They mirror definitions-worker/src/template.ts.
+export interface AttributeDef {
+  name: string;
+  label: string;
+  description?: string;
+  type: 'enum' | 'string' | 'number' | 'integer' | 'boolean';
+  unit?: string;
+  options?: string[];
+  minimum?: number;
+  maximum?: number;
+  variesByTrim?: boolean;
+}
+
+export interface DeviceType {
+  id: string;
+  name: string;
+  attributes: AttributeDef[];
+}
+
+// What Console is allowed to send. version, createdAt and updatedAt are
+// server-owned and the worker rejects them outright; author is stamped from
+// the session in src/app/api/templates/[id]/route.ts and is never client input.
+export type TemplatePayload = Omit<
+  Template,
+  'version' | 'createdAt' | 'updatedAt' | 'author'
+>;
diff --git a/src/utils/__fixtures__/toyota_camry_2020.json b/src/utils/__fixtures__/toyota_camry_2020.json
new file mode 100644
index 00000000..858cb14f
--- /dev/null
+++ b/src/utils/__fixtures__/toyota_camry_2020.json
@@ -0,0 +1,160 @@
+{
+  "id": "toyota_camry_2020",
+  "deviceType": "vehicle",
+  "manufacturer": {
+    "slug": "toyota",
+    "name": "Toyota",
+    "tokenId": 131
+  },
+  "model": "Camry",
+  "year": 2020,
+  "hardwareTemplateId": "130",
+  "attributes": {
+    "number_of_doors": 4,
+    "vehicle_type": "sedan",
+    "wheelbase_in": 111
+  },
+  "trims": [
+    {
+      "name": "LE",
+      "selectors": {
+        "manufacturerCode": ["2532"]
+      },
+      "attributes": {
+        "powertrain_type": "ICE",
+        "fuel_type": "gasoline",
+        "driven_wheels": "FWD",
+        "fuel_tank_capacity_gal": 16,
+        "mpg_city": 28,
+        "mpg_highway": 39,
+        "mpg_combined": 32,
+        "base_msrp": 24970
+      }
+    },
+    {
+      "name": "SE",
+      "selectors": {
+        "manufacturerCode": ["2546"]
+      },
+      "attributes": {
+        "powertrain_type": "ICE",
+        "fuel_type": "gasoline",
+        "driven_wheels": "FWD",
+        "fuel_tank_capacity_gal": 16,
+        "base_msrp": 26170
+      }
+    },
+    {
+      "name": "SE Nightshade",
+      "selectors": {
+        "manufacturerCode": ["2536"]
+      },
+      "attributes": {
+        "powertrain_type": "ICE",
+        "fuel_type": "gasoline",
+        "driven_wheels": "FWD",
+        "fuel_tank_capacity_gal": 16
+      }
+    },
+    {
+      "name": "XLE",
+      "selectors": {
+        "manufacturerCode": ["2517"]
+      },
+      "attributes": {
+        "powertrain_type": "ICE",
+        "fuel_type": "gasoline",
+        "driven_wheels": "AWD",
+        "fuel_tank_capacity_gal": 16,
+        "base_msrp": 30855
+      }
+    },
+    {
+      "name": "XSE",
+      "selectors": {
+        "manufacturerCode": ["2548"]
+      },
+      "attributes": {
+        "powertrain_type": "ICE",
+        "fuel_type": "gasoline",
+        "driven_wheels": "FWD",
+        "fuel_tank_capacity_gal": 16,
+        "mpg_city": 27,
+        "mpg_highway": 38,
+        "mpg_combined": 31,
+        "base_msrp": 30005
+      }
+    },
+    {
+      "name": "TRD V6",
+      "selectors": {
+        "manufacturerCode": ["2549"]
+      },
+      "attributes": {
+        "powertrain_type": "ICE",
+        "fuel_type": "gasoline",
+        "driven_wheels": "FWD",
+        "fuel_tank_capacity_gal": 16
+      }
+    },
+    {
+      "name": "XSE V6",
+      "selectors": {
+        "manufacturerCode": ["2550"]
+      },
+      "attributes": {
+        "powertrain_type": "ICE",
+        "fuel_type": "gasoline",
+        "driven_wheels": "FWD",
+        "fuel_tank_capacity_gal": 16,
+        "base_msrp": 35130
+      }
+    },
+    {
+      "name": "Hybrid LE",
+      "selectors": {
+        "manufacturerCode": ["2559"]
+      },
+      "attributes": {
+        "powertrain_type": "HEV",
+        "fuel_type": "gasoline",
+        "driven_wheels": "FWD",
+        "fuel_tank_capacity_gal": 13.2,
+        "base_msrp": 28430
+      }
+    },
+    {
+      "name": "Hybrid SE",
+      "selectors": {
+        "manufacturerCode": ["2561"]
+      },
+      "attributes": {
+        "powertrain_type": "HEV",
+        "fuel_type": "gasoline",
+        "driven_wheels": "FWD",
+        "fuel_tank_capacity_gal": 13.2,
+        "base_msrp": 30130
+      }
+    },
+    {
+      "name": "Hybrid XLE",
+      "selectors": {
+        "manufacturerCode": ["2560"]
+      },
+      "attributes": {
+        "powertrain_type": "HEV",
+        "fuel_type": "gasoline",
+        "driven_wheels": "FWD",
+        "fuel_tank_capacity_gal": 13.2,
+        "mpg_city": 44,
+        "mpg_highway": 47,
+        "mpg_combined": 46,
+        "base_msrp": 32730
+      }
+    }
+  ],
+  "version": 1,
+  "author": "0x0000000000000000000000000000000000000000",
+  "createdAt": "2026-08-26T00:00:00.000Z",
+  "updatedAt": "2026-08-26T00:00:00.000Z"
+}
diff --git a/src/utils/__fixtures__/vehicleVocab.ts b/src/utils/__fixtures__/vehicleVocab.ts
new file mode 100644
index 00000000..71dcdaee
--- /dev/null
+++ b/src/utils/__fixtures__/vehicleVocab.ts
@@ -0,0 +1,139 @@
+import type { DeviceType } from '@/types/template';
+
+// Copied verbatim from definitions-worker/schema/device-type-vehicle.json. A test
+// fixture only -- the running app always fetches the live vocabulary from the
+// worker, so this copy cannot change what the editor offers.
+export const vehicleVocab: DeviceType = {
+  id: 'vehicle',
+  name: 'Vehicle',
+  attributes: [
+    {
+      name: 'powertrain_type',
+      label: 'Powertrain',
+      description: 'Primary propulsion system.',
+      type: 'enum',
+      variesByTrim: true,
+      options: ['ICE', 'HEV', 'PHEV', 'BEV', 'FCEV'],
+    },
+    {
+      name: 'fuel_type',
+      label: 'Fuel',
+      description: 'Fuel the vehicle consumes.',
+      type: 'enum',
+      variesByTrim: true,
+      options: ['gasoline', 'diesel', 'electric', 'flex_fuel', 'hydrogen', 'cng', 'lpg'],
+    },
+    {
+      name: 'driven_wheels',
+      label: 'Drive',
+      description: 'Which wheels receive power.',
+      type: 'enum',
+      variesByTrim: true,
+      options: ['FWD', 'RWD', 'AWD', '4WD'],
+    },
+    {
+      name: 'vehicle_type',
+      label: 'Body style',
+      type: 'enum',
+      variesByTrim: true,
+      options: [
+        'sedan',
+        'hatchback',
+        'wagon',
+        'coupe',
+        'convertible',
+        'suv',
+        'minivan',
+        'van',
+        'pickup',
+        'truck',
+        'motorcycle',
+        'chassis_cab',
+        'other',
+      ],
+    },
+    {
+      name: 'number_of_doors',
+      label: 'Doors',
+      type: 'integer',
+      minimum: 0,
+      maximum: 8,
+    },
+    {
+      name: 'base_msrp',
+      label: 'Base MSRP',
+      type: 'number',
+      unit: 'USD',
+      minimum: 0,
+      variesByTrim: true,
+    },
+    {
+      name: 'fuel_tank_capacity_gal',
+      label: 'Fuel tank capacity',
+      type: 'number',
+      unit: 'gal',
+      minimum: 0,
+      maximum: 200,
+      variesByTrim: true,
+    },
+    {
+      name: 'battery_capacity_kwh',
+      label: 'Battery capacity',
+      type: 'number',
+      unit: 'kWh',
+      minimum: 0,
+      maximum: 500,
+      variesByTrim: true,
+    },
+    {
+      name: 'mpg_city',
+      label: 'MPG city',
+      type: 'number',
+      unit: 'mpg',
+      minimum: 0,
+      maximum: 200,
+      variesByTrim: true,
+    },
+    {
+      name: 'mpg_highway',
+      label: 'MPG highway',
+      type: 'number',
+      unit: 'mpg',
+      minimum: 0,
+      maximum: 200,
+      variesByTrim: true,
+    },
+    {
+      name: 'mpg_combined',
+      label: 'MPG combined',
+      type: 'number',
+      unit: 'mpg',
+      minimum: 0,
+      maximum: 200,
+      variesByTrim: true,
+    },
+    {
+      name: 'wheelbase_in',
+      label: 'Wheelbase',
+      type: 'number',
+      unit: 'in',
+      minimum: 0,
+      maximum: 400,
+      variesByTrim: true,
+    },
+    {
+      name: 'manufacturer_code',
+      label: 'OEM model code',
+      description: "Manufacturer's own code for this trim. Used to match a decoded VIN.",
+      type: 'string',
+      variesByTrim: true,
+    },
+    {
+      name: 'emissions_standard',
+      label: 'Emissions standard',
+      type: 'enum',
+      variesByTrim: true,
+      options: ['euro_4', 'euro_5', 'euro_6', 'euro_6d', 'tier_2', 'tier_3', 'other'],
+    },
+  ],
+};
diff --git a/src/utils/__tests__/templateCoerce.test.ts b/src/utils/__tests__/templateCoerce.test.ts
new file mode 100644
index 00000000..874bf159
--- /dev/null
+++ b/src/utils/__tests__/templateCoerce.test.ts
@@ -0,0 +1,79 @@
+import { coerce } from '../templateCoerce';
+import { vehicleVocab } from '../__fixtures__/vehicleVocab';
+
+const def = (name: string) => vehicleVocab.attributes.find((a) => a.name === name)!;
+
+describe('coerce', () => {
+  it('parses a stringified number into a number and says it did', () => {
+    expect(coerce(def('fuel_tank_capacity_gal'), '15.800000')).toEqual({
+      kind: 'value',
+      value: 15.8,
+      note: {
+        attribute: 'fuel_tank_capacity_gal',
+        from: '15.800000',
+        to: 15.8,
+        reason: 'stored as the number 15.8, not the text "15.800000"',
+      },
+    });
+  });
+
+  it('does not report a note when nothing was changed', () => {
+    expect(coerce(def('mpg_city'), '28')).toEqual({ kind: 'value', value: 28 });
+  });
+
+  it('treats an empty or whitespace input as a removal, never as an empty value', () => {
+    for (const raw of ['', '   ']) {
+      expect(coerce(def('mpg_city'), raw)).toEqual({
+        kind: 'clear',
+        note: {
+          attribute: 'mpg_city',
+          from: raw,
+          to: null,
+          reason: 'cleared — the attribute is removed, not stored empty',
+        },
+      });
+    }
+  });
+
+  it('refuses a value outside the vocabulary bounds with the reason', () => {
+    expect(coerce(def('mpg_city'), '400')).toEqual({
+      kind: 'error',
+      message: 'template: "mpg_city" above maximum 200',
+    });
+  });
+
+  it('refuses a non-integer for an integer attribute', () => {
+    expect(coerce(def('number_of_doors'), '4.5')).toEqual({
+      kind: 'error',
+      message: 'template: "number_of_doors" must be an integer',
+    });
+  });
+
+  it('refuses a value outside an enum options list', () => {
+    expect(coerce(def('powertrain_type'), 'Hybrid')).toEqual({
+      kind: 'error',
+      message:
+        'template: "powertrain_type"="Hybrid" is not one of ["ICE","HEV","PHEV","BEV","FCEV"]',
+    });
+  });
+
+  it('names the trim when one is given', () => {
+    expect(coerce(def('mpg_city'), '400', 'trim LE')).toEqual({
+      kind: 'error',
+      message: 'trim LE: "mpg_city" above maximum 200',
+    });
+  });
+
+  it('trims surrounding whitespace on a string attribute and says it did', () => {
+    expect(coerce(def('manufacturer_code'), '  2532 ')).toEqual({
+      kind: 'value',
+      value: '2532',
+      note: {
+        attribute: 'manufacturer_code',
+        from: '  2532 ',
+        to: '2532',
+        reason: 'surrounding whitespace removed',
+      },
+    });
+  });
+});
diff --git a/src/utils/__tests__/templateGrid.test.ts b/src/utils/__tests__/templateGrid.test.ts
new file mode 100644
index 00000000..97372c5e
--- /dev/null
+++ b/src/utils/__tests__/templateGrid.test.ts
@@ -0,0 +1,153 @@
+import camry from '../__fixtures__/toyota_camry_2020.json';
+import { vehicleVocab } from '../__fixtures__/vehicleVocab';
+import {
+  buildGrid,
+  setShared,
+  clearShared,
+  setTrimValue,
+  clearTrimValue,
+  liftToShared,
+  pushDownToTrims,
+  addTrim,
+  removeTrim,
+  hasEffectiveSelector,
+  toPayload,
+} from '../templateGrid';
+import type { Template } from '@/types/template';
+
+const t = camry as unknown as Template;
+const row = (tpl: Template, name: string) =>
+  buildGrid(tpl, vehicleVocab).rows.find((r) => r.def.name === name)!;
+
+describe('buildGrid', () => {
+  it('renders every vocabulary attribute, including ones the template does not set', () => {
+    const grid = buildGrid(t, vehicleVocab);
+    expect(grid.rows).toHaveLength(vehicleVocab.attributes.length);
+    expect(grid.rows.map((r) => r.def.name)).toEqual(
+      vehicleVocab.attributes.map((a) => a.name),
+    );
+    expect(row(t, 'emissions_standard').scope).toBe('absent');
+  });
+
+  it('names the two attributes the production record blended', () => {
+    // toyota_camry_2020 in production says powertrain_type ICE with hybrid
+    // tank and mpg figures. In the template those are the divergent rows, and
+    // this test is the regression that says so.
+    expect(row(t, 'powertrain_type').distinct).toBeGreaterThan(1);
+    expect(row(t, 'fuel_tank_capacity_gal').distinct).toBeGreaterThan(1);
+  });
+
+  it('counts shared attributes as one value and offers no lift', () => {
+    const doors = row(t, 'number_of_doors');
+    expect(doors.scope).toBe('shared');
+    expect(doors.shared).toBe(4);
+    expect(doors.distinct).toBe(1);
+    expect(doors.canLift).toBe(false);
+  });
+
+  it('offers a lift only when every trim agrees and none is absent', () => {
+    let all = t;
+    all.trims.forEach((_, i) => {
+      all = setTrimValue(all, i, 'mpg_highway', 39);
+    });
+    expect(row(all, 'mpg_highway').canLift).toBe(true);
+
+    const oneMissing = clearTrimValue(all, 3, 'mpg_highway');
+    expect(row(oneMissing, 'mpg_highway').canLift).toBe(false);
+    expect(row(oneMissing, 'mpg_highway').absentCount).toBe(1);
+  });
+});
+
+describe('the template-or-trim invariant', () => {
+  it('setting one trim value pushes a shared attribute down to every trim first', () => {
+    const next = setTrimValue(t, 0, 'number_of_doors', 2);
+    expect(next.attributes.number_of_doors).toBeUndefined();
+    expect(next.trims[0].attributes.number_of_doors).toBe(2);
+    next.trims
+      .slice(1)
+      .forEach((trim) => expect(trim.attributes.number_of_doors).toBe(4));
+  });
+
+  it('setting a shared value clears the attribute from every trim', () => {
+    const next = setShared(t, 'powertrain_type', 'ICE');
+    expect(next.attributes.powertrain_type).toBe('ICE');
+    next.trims.forEach((trim) => expect(trim.attributes.powertrain_type).toBeUndefined());
+  });
+
+  it('lift and push down are inverses', () => {
+    const pushed = pushDownToTrims(t, 'number_of_doors');
+    expect(pushed.attributes.number_of_doors).toBeUndefined();
+    const lifted = liftToShared(pushed, 'number_of_doors');
+    expect(lifted.attributes.number_of_doors).toBe(4);
+    lifted.trims.forEach((trim) =>
+      expect(trim.attributes.number_of_doors).toBeUndefined(),
+    );
+  });
+
+  it('never mutates the template it was given', () => {
+    const before = JSON.stringify(t);
+    setTrimValue(t, 0, 'mpg_city', 99);
+    setShared(t, 'mpg_city', 99);
+    clearShared(t, 'number_of_doors');
+    removeTrim(t, 0);
+    expect(JSON.stringify(t)).toBe(before);
+  });
+});
+
+describe('absent is not empty', () => {
+  it('clearing removes the key rather than storing an empty value', () => {
+    const cleared = clearTrimValue(t, 0, 'mpg_city');
+    expect('mpg_city' in cleared.trims[0].attributes).toBe(false);
+    expect(JSON.stringify(cleared)).not.toContain('""');
+  });
+
+  it('toPayload drops server-owned fields and empty selector containers', () => {
+    const withEmpties = degenerateSelectorOnFirstTrim(t);
+    const payload = toPayload(withEmpties) as unknown as Record<string, unknown>;
+    expect(payload.version).toBeUndefined();
+    expect(payload.createdAt).toBeUndefined();
+    expect(payload.updatedAt).toBeUndefined();
+    expect(payload.author).toBeUndefined();
+    const trims = payload.trims as { selectors?: unknown }[];
+    expect(trims[0].selectors).toBeUndefined();
+  });
+});
+
+describe('hasEffectiveSelector — gate 4', () => {
+  it.each([
+    [undefined, false],
+    [{}, false],
+    [{ manufacturerCode: [] }, false],
+    [{ manufacturerCode: [''] }, false],
+    [{ manufacturerCode: ['   '] }, false],
+    [{ styleName: [''] }, false],
+    [{ vinPattern: '' }, false],
+    [{ vinPattern: '   ' }, false],
+    [{ manufacturerCode: ['2532'] }, true],
+    [{ styleName: ['Hybrid LE'] }, true],
+    [{ vinPattern: '^4T1B11HK.*$' }, true],
+  ])('%p -> %p', (selectors, expected) => {
+    expect(hasEffectiveSelector(selectors as never)).toBe(expected);
+  });
+});
+
+describe('trims', () => {
+  it('addTrim appends an empty, selector-less, uniquely named trim', () => {
+    const next = addTrim(t, 'XLE V6');
+    expect(next.trims).toHaveLength(t.trims.length + 1);
+    expect(next.trims.at(-1)).toEqual({ name: 'XLE V6', attributes: {} });
+  });
+
+  it('removeTrim keeps at least one trim', () => {
+    const single = { ...t, trims: [t.trims[0]] };
+    expect(removeTrim(single, 0).trims).toHaveLength(1);
+  });
+});
+
+/** Puts a degenerate selector on trim 0 so toPayload has something to drop. */
+function degenerateSelectorOnFirstTrim(template: Template): Template {
+  const trims = template.trims.map((trim, i) =>
+    i === 0 ? { ...trim, selectors: { manufacturerCode: [''] } } : trim,
+  );
+  return { ...template, trims };
+}
diff --git a/src/utils/__tests__/templateValidate.test.ts b/src/utils/__tests__/templateValidate.test.ts
new file mode 100644
index 00000000..e63588d7
--- /dev/null
+++ b/src/utils/__tests__/templateValidate.test.ts
@@ -0,0 +1,91 @@
+import camry from '../__fixtures__/toyota_camry_2020.json';
+import { vehicleVocab } from '../__fixtures__/vehicleVocab';
+import { validateDraft } from '../templateValidate';
+import { addTrim, setTrimValue, renameTrim, setSelectors } from '../templateGrid';
+import type { Template } from '@/types/template';
+
+const t = camry as unknown as Template;
+
+describe('validateDraft', () => {
+  it('passes the real Camry', () => {
+    expect(validateDraft(t, vehicleVocab)).toEqual([]);
+  });
+
+  it('reports a selector-less trim on a multi-trim template, in the worker words', () => {
+    const withNew = addTrim(t, 'XLE V6');
+    expect(validateDraft(withNew, vehicleVocab)).toContain(
+      'trim XLE V6: selectors are required — a template with more than one trim cannot have a ' +
+        'selector-less trim, which would match every signal and make every decode ambiguous',
+    );
+  });
+
+  it.each([[{}], [{ manufacturerCode: [''] }], [{ vinPattern: '   ' }]])(
+    'treats the degenerate selector %p as no selector at all',
+    (selectors) => {
+      const withNew = setSelectors(
+        addTrim(t, 'XLE V6'),
+        t.trims.length,
+        selectors as never,
+      );
+      expect(
+        validateDraft(withNew, vehicleVocab).some((e) =>
+          e.includes('selectors are required'),
+        ),
+      ).toBe(true);
+    },
+  );
+
+  it('accepts a selector-less trim when it is the only trim', () => {
+    const single = { ...t, trims: [{ name: 'LE', attributes: {} }] } as Template;
+    expect(validateDraft(single, vehicleVocab)).toEqual([]);
+  });
+
+  it('reports an attribute on both the template and a trim', () => {
+    const both = {
+      ...t,
+      attributes: { ...t.attributes, powertrain_type: 'ICE' },
+    } as Template;
+    expect(validateDraft(both, vehicleVocab)).toContain(
+      '"powertrain_type" is on both the template and trim LE — pick one',
+    );
+  });
+
+  it('reports duplicate trim names and duplicate manufacturer codes', () => {
+    const dupName = renameTrim(t, 1, t.trims[0].name);
+    expect(validateDraft(dupName, vehicleVocab)).toContain(
+      `duplicate trim name "${t.trims[0].name}" — trim names must be unique`,
+    );
+
+    const code = t.trims[0].selectors!.manufacturerCode![0];
+    const dupCode = setSelectors(t, 1, { manufacturerCode: [code] });
+    expect(validateDraft(dupCode, vehicleVocab)).toContain(
+      `manufacturerCode ${code} is claimed by both "${t.trims[0].name}" and "${t.trims[1].name}"`,
+    );
+  });
+
+  it('reports an unnamed trim, an empty trims array, and an id/year disagreement', () => {
+    expect(validateDraft(renameTrim(t, 0, ''), vehicleVocab)).toContain(
+      'each trim needs a name',
+    );
+    expect(validateDraft({ ...t, trims: [] } as Template, vehicleVocab)).toContain(
+      'trims must contain at least one trim',
+    );
+    expect(validateDraft({ ...t, year: 2021 } as Template, vehicleVocab)).toContain(
+      'year 2021 does not match the year in id "toyota_camry_2020"',
+    );
+  });
+
+  it('reports an out-of-vocabulary value with the trim named', () => {
+    const bad = setTrimValue(t, 0, 'mpg_city', 400);
+    expect(validateDraft(bad, vehicleVocab)).toContain(
+      'trim LE: "mpg_city" above maximum 200',
+    );
+  });
+
+  it('says nothing about hardwareTemplateId, which is not a vocabulary attribute', () => {
+    const hw = { ...t, hardwareTemplateId: '130' } as Template;
+    expect(
+      validateDraft(hw, vehicleVocab).some((e) => e.includes('hardwareTemplateId')),
+    ).toBe(false);
+  });
+});
diff --git a/src/utils/templateCoerce.ts b/src/utils/templateCoerce.ts
new file mode 100644
index 00000000..2bb2765e
--- /dev/null
+++ b/src/utils/templateCoerce.ts
@@ -0,0 +1,110 @@
+import type { AttributeDef, AttributeValue } from '@/types/template';
+
+export interface Normalisation {
+  attribute: string;
+  from: string;
+  /** null means the attribute was removed. */
+  to: AttributeValue | null;
+  reason: string;
+}
+
+export type CoerceResult =
+  | { kind: 'value'; value: AttributeValue; note?: Normalisation }
+  | { kind: 'clear'; note: Normalisation }
+  | { kind: 'error'; message: string };
+
+/**
+ * One text input becomes one typed attribute value, or a removal, or a named
+ * refusal. Never silently: every difference between what was typed and what
+ * gets stored produces a Normalisation, which NormalisationPanel shows before
+ * save. Error messages are the worker's own strings (see
+ * definitions-worker/src/template.ts checkAttributes) so the editor and the
+ * validator never describe the same fault two different ways. `where` names the
+ * place the way the worker does — 'template' or 'trim LE'.
+ */
+export function coerce(def: AttributeDef, raw: string, where = 'template'): CoerceResult {
+  const trimmed = raw.trim();
+
+  if (trimmed === '') {
+    return {
+      kind: 'clear',
+      note: {
+        attribute: def.name,
+        from: raw,
+        to: null,
+        reason: 'cleared — the attribute is removed, not stored empty',
+      },
+    };
+  }
+
+  switch (def.type) {
+    case 'enum': {
+      const options = def.options ?? [];
+      if (!options.includes(trimmed)) {
+        return {
+          kind: 'error',
+          message: `${where}: "${def.name}"=${JSON.stringify(trimmed)} is not one of ${JSON.stringify(options)}`,
+        };
+      }
+      return { kind: 'value', value: trimmed };
+    }
+    case 'number':
+    case 'integer': {
+      const n = Number(trimmed);
+      if (!Number.isFinite(n)) {
+        return {
+          kind: 'error',
+          message: `${where}: "${def.name}" must be a number, got ${JSON.stringify(raw)}`,
+        };
+      }
+      if (def.type === 'integer' && !Number.isInteger(n)) {
+        return { kind: 'error', message: `${where}: "${def.name}" must be an integer` };
+      }
+      if (def.minimum !== undefined && n < def.minimum) {
+        return {
+          kind: 'error',
+          message: `${where}: "${def.name}" below minimum ${def.minimum}`,
+        };
+      }
+      if (def.maximum !== undefined && n > def.maximum) {
+        return {
+          kind: 'error',
+          message: `${where}: "${def.name}" above maximum ${def.maximum}`,
+        };
+      }
+      // 6% of the old catalog stored numbers as strings like "15.800000".
+      // Reporting the reparse is how a contributor learns the value is typed.
+      return String(n) === raw
+        ? { kind: 'value', value: n }
+        : {
+            kind: 'value',
+            value: n,
+            note: {
+              attribute: def.name,
+              from: raw,
+              to: n,
+              reason: `stored as the number ${n}, not the text ${JSON.stringify(raw.trim())}`,
+            },
+          };
+    }
+    case 'boolean': {
+      if (trimmed === 'true') return { kind: 'value', value: true };
+      if (trimmed === 'false') return { kind: 'value', value: false };
+      return { kind: 'error', message: `${where}: "${def.name}" must be a boolean` };
+    }
+    case 'string':
+    default:
+      return trimmed === raw
+        ? { kind: 'value', value: trimmed }
+        : {
+            kind: 'value',
+            value: trimmed,
+            note: {
+              attribute: def.name,
+              from: raw,
+              to: trimmed,
+              reason: 'surrounding whitespace removed',
+            },
+          };
+  }
+}
diff --git a/src/utils/templateGrid.ts b/src/utils/templateGrid.ts
new file mode 100644
index 00000000..eb30a10d
--- /dev/null
+++ b/src/utils/templateGrid.ts
@@ -0,0 +1,233 @@
+import type {
+  AttributeDef,
+  AttributeValue,
+  DeviceType,
+  Template,
+  TemplatePayload,
+  Trim,
+  TrimSelectors,
+} from '@/types/template';
+
+export type Scope = 'shared' | 'trim' | 'absent';
+
+export interface GridRow {
+  def: AttributeDef;
+  scope: Scope;
+  shared?: AttributeValue;
+  /** One entry per trim, in trim order. `undefined` means not set — never ''. */
+  cells: (AttributeValue | undefined)[];
+  /** Distinct values across trims. 1 on a shared row: that is the point of shared. */
+  distinct: number;
+  absentCount: number;
+  canLift: boolean;
+}
+
+export interface Grid {
+  trims: Trim[];
+  rows: GridRow[];
+}
+
+const attrs = (map: Record<string, AttributeValue> | undefined) => map ?? {};
+
+/**
+ * Rows follow vocabulary order, always. Sorting divergent rows to the top would
+ * move an attribute every time someone edited it; the design puts the emphasis
+ * on contrast instead, so positions stay learnable. Every vocabulary attribute
+ * gets a row even when nothing sets it — 5,152 templates in the current emitted
+ * set carry no attributes at all, so "empty" is the common case and an empty
+ * row is the affordance for filling it in.
+ */
+export function buildGrid(template: Template, vocab: DeviceType): Grid {
+  const rows = vocab.attributes.map<GridRow>((def) => {
+    const shared = attrs(template.attributes)[def.name];
+    const cells = template.trims.map((t) => attrs(t.attributes)[def.name]);
+    const present = cells.filter((v): v is AttributeValue => v !== undefined);
+    const distinct = new Set(present.map((v) => JSON.stringify(v))).size;
+    const scope: Scope =
+      shared !== undefined ? 'shared' : present.length > 0 ? 'trim' : 'absent';
+    return {
+      def,
+      scope,
+      ...(shared !== undefined ? { shared } : {}),
+      cells,
+      distinct: scope === 'shared' ? 1 : distinct,
+      absentCount: scope === 'shared' ? 0 : cells.length - present.length,
+      // Lifting a single-trim template's attribute changes nothing, so the
+      // offer would be pure noise. Only worth surfacing where agreement is a
+      // fact about several trims.
+      canLift:
+        scope === 'trim' &&
+        distinct === 1 &&
+        present.length === cells.length &&
+        cells.length > 1,
+    };
+  });
+  return { trims: template.trims, rows };
+}
+
+const withoutKey = (map: Record<string, AttributeValue>, key: string) => {
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  const { [key]: _dropped, ...rest } = map;
+  return rest;
+};
+
+const mapTrims = (t: Template, fn: (trim: Trim, index: number) => Trim): Template => ({
+  ...t,
+  trims: t.trims.map(fn),
+});
+
+/** Shared value wins outright: the attribute cannot also live on a trim. */
+export function setShared(t: Template, name: string, value: AttributeValue): Template {
+  const next = mapTrims(t, (trim) => ({
+    ...trim,
+    attributes: withoutKey(attrs(trim.attributes), name),
+  }));
+  return { ...next, attributes: { ...attrs(t.attributes), [name]: value } };
+}
+
+export function clearShared(t: Template, name: string): Template {
+  return { ...t, attributes: withoutKey(attrs(t.attributes), name) };
+}
+
+/**
+ * The move that makes divergence expressible. If the attribute is currently
+ * shared, it is pushed down onto every trim first — otherwise the result would
+ * carry the attribute in both places, which the worker rejects with
+ * `"<k>" is on both the template and trim <name> — pick one`.
+ */
+export function setTrimValue(
+  t: Template,
+  index: number,
+  name: string,
+  value: AttributeValue,
+): Template {
+  const base = attrs(t.attributes)[name] !== undefined ? pushDownToTrims(t, name) : t;
+  return mapTrims(base, (trim, i) =>
+    i === index
+      ? { ...trim, attributes: { ...attrs(trim.attributes), [name]: value } }
+      : trim,
+  );
+}
+
+/** Removes the key. There is no empty value to store. */
+export function clearTrimValue(t: Template, index: number, name: string): Template {
+  return mapTrims(t, (trim, i) =>
+    i === index
+      ? { ...trim, attributes: withoutKey(attrs(trim.attributes), name) }
+      : trim,
+  );
+}
+
+export function pushDownToTrims(t: Template, name: string): Template {
+  const value = attrs(t.attributes)[name];
+  if (value === undefined) return t;
+  const next = mapTrims(t, (trim) => ({
+    ...trim,
+    attributes: { ...attrs(trim.attributes), [name]: value },
+  }));
+  return { ...next, attributes: withoutKey(attrs(t.attributes), name) };
+}
+
+/** The correct modelling action when the divergence rail reads 1. */
+export function liftToShared(t: Template, name: string): Template {
+  const values = t.trims.map((trim) => attrs(trim.attributes)[name]);
+  if (values.some((v) => v === undefined)) return t;
+  if (new Set(values.map((v) => JSON.stringify(v))).size !== 1) return t;
+  const next = mapTrims(t, (trim) => ({
+    ...trim,
+    attributes: withoutKey(attrs(trim.attributes), name),
+  }));
+  return {
+    ...next,
+    attributes: { ...attrs(t.attributes), [name]: values[0] as AttributeValue },
+  };
+}
+
+export function addTrim(t: Template, name: string): Template {
+  return { ...t, trims: [...t.trims, { name, attributes: {} }] };
+}
+
+/** The schema requires minItems 1: a model-year sold one way still has a trim. */
+export function removeTrim(t: Template, index: number): Template {
+  if (t.trims.length <= 1) return t;
+  return { ...t, trims: t.trims.filter((_, i) => i !== index) };
+}
+
+export function renameTrim(t: Template, index: number, name: string): Template {
+  return mapTrims(t, (trim, i) => (i === index ? { ...trim, name } : trim));
+}
+
+export function setSelectors(
+  t: Template,
+  index: number,
+  selectors: TrimSelectors,
+): Template {
+  return mapTrims(t, (trim, i) => (i === index ? { ...trim, selectors } : trim));
+}
+
+export function setHardwareTemplateId(t: Template, value: string | undefined): Template {
+  if (value === undefined || value === '') {
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    const { hardwareTemplateId: _dropped, ...rest } = t;
+    return rest as Template;
+  }
+  return { ...t, hardwareTemplateId: value };
+}
+
+/**
+ * Mirrors definitions-worker/src/template.ts hasSelector, degenerate cases
+ * included. A trim that fails this on a multi-trim template matches every
+ * signal and makes every decode for the model-year ambiguous.
+ */
+export function hasEffectiveSelector(selectors?: TrimSelectors): boolean {
+  if (!selectors) return false;
+  if (selectors.manufacturerCode?.some((c) => c.trim().length > 0)) return true;
+  if (selectors.styleName?.some((n) => n.trim().length > 0)) return true;
+  return (
+    typeof selectors.vinPattern === 'string' && selectors.vinPattern.trim().length > 0
+  );
+}
+
+const pruneSelectors = (selectors?: TrimSelectors): TrimSelectors | undefined => {
+  if (!selectors) return undefined;
+  const out: TrimSelectors = {};
+  const codes =
+    selectors.manufacturerCode?.map((c) => c.trim()).filter((c) => c.length > 0) ?? [];
+  const names =
+    selectors.styleName?.map((n) => n.trim()).filter((n) => n.length > 0) ?? [];
+  if (codes.length > 0) out.manufacturerCode = codes;
+  if (names.length > 0) out.styleName = names;
+  if (selectors.vinPattern && selectors.vinPattern.trim().length > 0) {
+    out.vinPattern = selectors.vinPattern.trim();
+  }
+  return Object.keys(out).length > 0 ? out : undefined;
+};
+
+/**
+ * What goes on the wire. version, createdAt and updatedAt are server-owned and
+ * the worker rejects them as unexpected top-level keys; author is stamped from
+ * the session server-side. Empty selector containers are dropped rather than
+ * sent — but dropping them does not make a selector-less trim legal, and
+ * templateValidate.ts is what says so before save.
+ */
+export function toPayload(t: Template): TemplatePayload {
+  // An omit list, not an allow list: a field added to the schema later should
+  // reach the worker, not be silently dropped here.
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  const { version: _v, createdAt: _c, updatedAt: _u, author: _a, ...rest } = t;
+  return {
+    ...rest,
+    attributes: attrs(t.attributes),
+    trims: t.trims.map((trim) => {
+      const selectors = pruneSelectors(trim.selectors);
+      return {
+        name: trim.name,
+        ...(selectors ? { selectors } : {}),
+        ...(trim.hardwareTemplateId
+          ? { hardwareTemplateId: trim.hardwareTemplateId }
+          : {}),
+        attributes: attrs(trim.attributes),
+      };
+    }),
+  };
+}
diff --git a/src/utils/templateValidate.ts b/src/utils/templateValidate.ts
new file mode 100644
index 00000000..0c42c73f
--- /dev/null
+++ b/src/utils/templateValidate.ts
@@ -0,0 +1,135 @@
+import type {
+  AttributeDef,
+  AttributeValue,
+  DeviceType,
+  Template,
+} from '@/types/template';
+import { hasEffectiveSelector } from '@/utils/templateGrid';
+
+const ID_RE = /^[a-z0-9][a-z0-9._&+-]*_[a-z0-9._&+-]+_[0-9]{4}$/;
+
+/**
+ * A mirror of definitions-worker/src/template.ts validateTemplate, restricted to
+ * the faults a person editing in Console can actually cause. It is NOT
+ * authoritative — the worker is, and the save path surfaces its 422 verbatim.
+ * Its job is to stop a doomed save and to name the fault in the same words the
+ * worker would, so nobody has to reconcile two vocabularies for one problem.
+ *
+ * When the worker's strings change, this file is the drift point. The strings
+ * below are copied verbatim from definitions-worker/src/template.ts; the tests
+ * in __tests__/templateValidate.test.ts are what catch the drift.
+ */
+export function validateDraft(template: Template, vocab: DeviceType): string[] {
+  const errs: string[] = [];
+  const vmap = new Map<string, AttributeDef>(vocab.attributes.map((a) => [a.name, a]));
+
+  if (!ID_RE.test(template.id)) errs.push('id must be <make>_<model>_<year>');
+  if (!template.model) errs.push('model is required');
+  if (ID_RE.test(template.id)) {
+    const idYear = Number(template.id.split('_').at(-1));
+    if (idYear !== template.year) {
+      errs.push(`year ${template.year} does not match the year in id "${template.id}"`);
+    }
+  }
+  if (!template.manufacturer?.slug || !template.manufacturer?.name) {
+    errs.push('manufacturer requires slug and name');
+  }
+  if (
+    template.hardwareTemplateId !== undefined &&
+    !/^[0-9]+$/.test(template.hardwareTemplateId)
+  ) {
+    errs.push('hardwareTemplateId must be a numeric string');
+  }
+
+  const templateAttrs = template.attributes ?? {};
+  checkAttributes(templateAttrs, vmap, 'template', errs);
+
+  if (!Array.isArray(template.trims) || template.trims.length === 0) {
+    errs.push('trims must contain at least one trim');
+    return errs;
+  }
+
+  const multiTrim = template.trims.length > 1;
+  const seenNames = new Set<string>();
+  const seenCodes = new Map<string, string>();
+
+  for (const trim of template.trims) {
+    const name = trim.name || '';
+    if (!name) errs.push('each trim needs a name');
+    if (name) {
+      if (seenNames.has(name))
+        errs.push(`duplicate trim name "${name}" — trim names must be unique`);
+      else seenNames.add(name);
+    }
+
+    const trimAttrs = trim.attributes ?? {};
+    checkAttributes(trimAttrs, vmap, `trim ${name || '?'}`, errs);
+    for (const k of Object.keys(trimAttrs)) {
+      if (k in templateAttrs) {
+        errs.push(`"${k}" is on both the template and trim ${name} — pick one`);
+      }
+    }
+
+    for (const code of trim.selectors?.manufacturerCode ?? []) {
+      const prev = seenCodes.get(code);
+      if (prev !== undefined) {
+        errs.push(`manufacturerCode ${code} is claimed by both "${prev}" and "${name}"`);
+      } else seenCodes.set(code, name);
+    }
+
+    if (multiTrim && !hasEffectiveSelector(trim.selectors)) {
+      errs.push(
+        `trim ${name || '?'}: selectors are required — a template with more than one trim cannot ` +
+          'have a selector-less trim, which would match every signal and make every decode ambiguous',
+      );
+    }
+  }
+
+  return errs;
+}
+
+function checkAttributes(
+  map: Record<string, AttributeValue>,
+  vmap: Map<string, AttributeDef>,
+  where: string,
+  errs: string[],
+): void {
+  for (const [k, v] of Object.entries(map)) {
+    const def = vmap.get(k);
+    if (!def) {
+      errs.push(`${where}: unknown attribute "${k}"`);
+      continue;
+    }
+    if (v === null || v === undefined || v === '' || v === '<nil>') {
+      errs.push(`${where}: "${k}" is empty — omit the attribute instead`);
+      continue;
+    }
+    switch (def.type) {
+      case 'enum':
+        if (typeof v !== 'string' || !(def.options ?? []).includes(v)) {
+          errs.push(
+            `${where}: "${k}"=${JSON.stringify(v)} is not one of ${JSON.stringify(def.options ?? [])}`,
+          );
+        }
+        break;
+      case 'number':
+      case 'integer':
+        if (typeof v !== 'number' || !Number.isFinite(v)) {
+          errs.push(`${where}: "${k}" must be a number, got ${JSON.stringify(v)}`);
+        } else if (def.type === 'integer' && !Number.isInteger(v)) {
+          errs.push(`${where}: "${k}" must be an integer`);
+        } else if (def.minimum !== undefined && v < def.minimum) {
+          errs.push(`${where}: "${k}" below minimum ${def.minimum}`);
+        } else if (def.maximum !== undefined && v > def.maximum) {
+          errs.push(`${where}: "${k}" above maximum ${def.maximum}`);
+        }
+        break;
+      case 'boolean':
+        if (typeof v !== 'boolean') errs.push(`${where}: "${k}" must be a boolean`);
+        break;
+      case 'string':
+        if (typeof v !== 'string') errs.push(`${where}: "${k}" must be a string`);
+        break;
+    }
+  }
+}