diff --git a/packages/void/src/asset-routing.ts b/packages/void/src/asset-routing.ts
index 42f15df0e..1078c6dfa 100644
--- a/packages/void/src/asset-routing.ts
+++ b/packages/void/src/asset-routing.ts
@@ -51,6 +51,16 @@ export function resolveAssetConfig(inputs: AssetRoutingInputs): AssetConfig {
   return resolveAssetRoutingPolicy(inputs).assetConfig;
 }
 
+// Void's reserved internal namespace (`/__void/ready`, `/__void/migrate/*`,
+// etc.). These must reach the worker before CF Static Assets can serve the SPA
+// shell — otherwise `not_found_handling: 'single-page-application'` returns
+// index.html for GET /__void/migrate/capabilities and migration capability
+// negotiation fails at deploy time. The worker-first (`/**`) branch already
+// covers it; both SPA-fallback branches must list it explicitly, since a SPA
+// can advertise migrations without API/auth routes (e.g. a cron/queue-only app
+// with D1 migrations still emits manifest.migrations).
+const VOID_INTERNAL_WORKER_FIRST = ['/__void', '/__void/*'];
+
 export function resolveAssetRoutingPolicy(inputs: AssetRoutingInputs): AssetRoutingPolicy {
   const workerFirst = workerOwnsHtmlRouting(inputs);
   const apiWorkerFirst =
@@ -58,8 +68,14 @@ export function resolveAssetRoutingPolicy(inputs: AssetRoutingInputs): AssetRout
   const assetConfig: AssetConfig = workerFirst
     ? { not_found_handling: 'none', run_worker_first: ['/**'] }
     : apiWorkerFirst
-      ? { not_found_handling: 'single-page-application', run_worker_first: ['/api', '/api/*'] }
-      : { not_found_handling: 'single-page-application' };
+      ? {
+          not_found_handling: 'single-page-application',
+          run_worker_first: ['/api', '/api/*', ...VOID_INTERNAL_WORKER_FIRST],
+        }
+      : {
+          not_found_handling: 'single-page-application',
+          run_worker_first: [...VOID_INTERNAL_WORKER_FIRST],
+        };
   return {
     assetConfig,
     apiWorkerFirst,
diff --git a/packages/void/test/integration/spa-middleware-auth.test.ts b/packages/void/test/integration/spa-middleware-auth.test.ts
index 3366e1868..05f393d5a 100644
--- a/packages/void/test/integration/spa-middleware-auth.test.ts
+++ b/packages/void/test/integration/spa-middleware-auth.test.ts
@@ -160,7 +160,7 @@ describe('SPA asset routing policy', () => {
 
     const assetConfig = readBuiltAssetConfig();
     expect(assetConfig.not_found_handling).toBe('single-page-application');
-    expect(assetConfig.run_worker_first).toEqual(['/api', '/api/*']);
+    expect(assetConfig.run_worker_first).toEqual(['/api', '/api/*', '/__void', '/__void/*']);
   });
 
   it('routes document routes through the worker before SPA fallback HTML', async () => {
diff --git a/packages/void/test/unit/deploy-asset-config.test.ts b/packages/void/test/unit/deploy-asset-config.test.ts
index 6b62d8b7e..bb314ff67 100644
--- a/packages/void/test/unit/deploy-asset-config.test.ts
+++ b/packages/void/test/unit/deploy-asset-config.test.ts
@@ -15,10 +15,13 @@ import {
 // worker does not need to inspect document navigations.
 describe('resolveAssetConfig', () => {
   const NONE = { not_found_handling: 'none' as const, run_worker_first: ['/**'] };
-  const SPA = { not_found_handling: 'single-page-application' as const };
+  const SPA = {
+    not_found_handling: 'single-page-application' as const,
+    run_worker_first: ['/__void', '/__void/*'],
+  };
   const SPA_API = {
     not_found_handling: 'single-page-application' as const,
-    run_worker_first: ['/api', '/api/*'],
+    run_worker_first: ['/api', '/api/*', '/__void', '/__void/*'],
   };
 
   it('uses none when SSR is enabled', () => {
@@ -55,6 +58,56 @@ describe('resolveAssetConfig', () => {
     ).toEqual(SPA_API);
   });
 
+  it('routes the /__void internal namespace to the worker for SPA + API apps', () => {
+    // Regression: a SPA app with API routes + D1 migrations lands in the
+    // apiWorkerFirst branch. Without /__void in run_worker_first, CF Static
+    // Assets serves index.html for GET /__void/migrate/capabilities before the
+    // worker runs, so the migration handler is never reached and the deploy
+    // fails with "migration protocol v2 capability negotiation failed".
+    const config = resolveAssetConfig({
+      isSsr: false,
+      hasPages: false,
+      hasApiRoutes: true,
+      hasDocumentRoutes: false,
+      hasMiddleware: false,
+    });
+    expect(config.not_found_handling).toBe('single-page-application');
+    expect(config.run_worker_first).toContain('/__void');
+    expect(config.run_worker_first).toContain('/__void/*');
+  });
+
+  it('routes the /__void internal namespace worker-first for auth-enabled SPA apps', () => {
+    // authEnabled also triggers the apiWorkerFirst branch (auth apps have
+    // migrations for the auth tables), so /__void must reach the worker too.
+    const config = resolveAssetConfig({
+      isSsr: false,
+      hasPages: false,
+      hasApiRoutes: false,
+      hasDocumentRoutes: false,
+      hasMiddleware: false,
+      authEnabled: true,
+    });
+    expect(config.run_worker_first).toContain('/__void/*');
+  });
+
+  it('routes the /__void internal namespace worker-first for a migration-only SPA (cron/queue app, no API/auth/pages)', () => {
+    // A SPA whose only server code is a cron/queue handler still advertises
+    // manifest.migrations (validatedMigrations is passed to buildVoidManifest
+    // independently of routes), but has none of the asset-routing flags, so it
+    // falls to the pure-SPA branch. Without /__void there, CF serves index.html
+    // for GET /__void/migrate/capabilities and negotiation fails. (Codex #250 P2)
+    const config = resolveAssetConfig({
+      isSsr: false,
+      hasPages: false,
+      hasApiRoutes: false,
+      hasDocumentRoutes: false,
+      hasMiddleware: false,
+    });
+    expect(config.not_found_handling).toBe('single-page-application');
+    expect(config.run_worker_first).toContain('/__void');
+    expect(config.run_worker_first).toContain('/__void/*');
+  });
+
   it('uses none when the project has document routes', () => {
     expect(
       resolveAssetConfig({
diff --git a/packages/void/test/unit/plugin-dev-asset-routing.test.ts b/packages/void/test/unit/plugin-dev-asset-routing.test.ts
index 9ad4de1e1..a9a28e6cc 100644
--- a/packages/void/test/unit/plugin-dev-asset-routing.test.ts
+++ b/packages/void/test/unit/plugin-dev-asset-routing.test.ts
@@ -196,7 +196,7 @@ describe('voidPlugin dev asset routing', () => {
     });
 
     expect(assets?.not_found_handling).toBe('single-page-application');
-    expect(assets?.run_worker_first).toEqual(['/api', '/api/*']);
+    expect(assets?.run_worker_first).toEqual(['/api', '/api/*', '/__void', '/__void/*']);
   });
 
   it('does not return existing D1 or R2 bindings when adding inferred defaults', async () => {
@@ -228,7 +228,7 @@ describe('voidPlugin dev asset routing', () => {
     const assets = await resolveVoidPluginAssets(root);
 
     expect(assets?.not_found_handling).toBe('single-page-application');
-    expect(assets?.run_worker_first).toEqual(['/api', '/api/*']);
+    expect(assets?.run_worker_first).toEqual(['/api', '/api/*', '/__void', '/__void/*']);
   });
 
   it('routes managed auth endpoints to the worker without making all documents worker-first', async () => {
@@ -236,7 +236,7 @@ describe('voidPlugin dev asset routing', () => {
     const assets = await resolveVoidPluginAssets(root);
 
     expect(assets?.not_found_handling).toBe('single-page-application');
-    expect(assets?.run_worker_first).toEqual(['/api', '/api/*']);
+    expect(assets?.run_worker_first).toEqual(['/api', '/api/*', '/__void', '/__void/*']);
   });
 
   it('keeps API-only projects static-first when middleware directory has no active files', async () => {
@@ -247,7 +247,7 @@ describe('voidPlugin dev asset routing', () => {
     const assets = await resolveVoidPluginAssets(root);
 
     expect(assets?.not_found_handling).toBe('single-page-application');
-    expect(assets?.run_worker_first).toEqual(['/api', '/api/*']);
+    expect(assets?.run_worker_first).toEqual(['/api', '/api/*', '/__void', '/__void/*']);
   });
 
   it('routes document routes through the worker before SPA fallback HTML', async () => {
diff --git a/packages/void/test/unit/plugin-routing.test.ts b/packages/void/test/unit/plugin-routing.test.ts
index 47023ecf2..6b5c37f8d 100644
--- a/packages/void/test/unit/plugin-routing.test.ts
+++ b/packages/void/test/unit/plugin-routing.test.ts
@@ -215,7 +215,7 @@ describe('routingPlugin', () => {
         apiWorkerFirst: true,
         assetConfig: expect.objectContaining({
           not_found_handling: 'single-page-application',
-          run_worker_first: ['/api', '/api/*'],
+          run_worker_first: ['/api', '/api/*', '/__void', '/__void/*'],
         }),
         workerFirst: false,
       }),