fix: default unknown models to the full prompt, single-source product identity and version

.gitkeep

@@ -0,0 +1 @@
+# .gitkeep file auto-generated at 2026-07-30T18:32:11.164Z for PR creation at branch issue-285-531ca23a5284 for issue https://github.com/link-assistant/agent/issues/285

js/.changeset/fix-unknown-model-prompt-branding-version.md

@@ -0,0 +1,17 @@
+---
+'@link-assistant/agent': patch
+---
+
+Fix three defects that made a session's behaviour unattributable (#285):
+
+- Unknown model ids no longer silently fall back to the without-todo prompt.
+  Prompt selection is now table-driven with an explicit, logged default
+  (`anthropic`, which includes the todo/task-tracking discipline). Models that
+  genuinely break on todo tools can opt out via `AGENT_SYSTEM_PROMPT`.
+- The product identity (name, repo, issues and docs URLs) lives in one module
+  and is substituted into prompts and tool descriptions at render time, so the
+  agent no longer tells users it is `opencode` or sends bug reports to
+  `sst/opencode`.
+- Session records report the real package version instead of the hard-coded
+  `agent-cli-1.0.0`; `--version`, the process log and session records now all
+  read the same value.

js/src/branding.ts

@@ -0,0 +1,47 @@
+/**
+ * Single source of truth for the product identity that is exposed to models
+ * and to users.
+ *
+ * Several system prompts in `src/session/prompt/*.txt` are kept byte-identical
+ * to their upstream (opencode) originals so they can be re-synced without
+ * conflicts. Instead of editing those files, the identity is substituted at
+ * render time by {@link applyBranding}, so a rename is one edit here rather
+ * than one edit per prompt file. See issue #285.
+ */
+export namespace Branding {
+  /** Product name as it should appear in prose. */
+  export const NAME = 'Agent';
+  /** Product name as it appears in a shell (the binary name). */
+  export const BINARY = 'agent';
+  /** Canonical source repository. */
+  export const REPO_URL = 'https://github.com/link-assistant/agent';
+  /** Where users should report issues with this tool. */
+  export const ISSUES_URL = 'https://github.com/link-assistant/agent/issues';
+  /** Where documentation about this tool lives. */
+  export const DOCS_URL = 'https://github.com/link-assistant/agent#readme';
+
+  /**
+   * Ordered replacements. URLs must be replaced before the bare product name,
+   * otherwise the name substitution would corrupt the URLs.
+   */
+  const REPLACEMENTS: [RegExp, string][] = [
+    [/https:\/\/github\.com\/sst\/opencode\/issues/gi, ISSUES_URL],
+    [/https:\/\/github\.com\/sst\/opencode/gi, REPO_URL],
+    [/https:\/\/opencode\.ai\/docs/gi, DOCS_URL],
+    [/https:\/\/opencode\.ai/gi, DOCS_URL],
+    [/sst\/opencode/gi, 'link-assistant/agent'],
+    [/opencode/gi, NAME],
+  ];
+
+  /**
+   * Replace every upstream product reference in `text` with this product's
+   * identity. Safe to call on text that contains no references.
+   */
+  export function apply(text: string): string {
+    let result = text;
+    for (const [pattern, replacement] of REPLACEMENTS) {
+      result = result.replace(pattern, replacement);
+    }
+    return result;
+  }
+}

js/src/index.js

@@ -46,22 +46,12 @@ import {
   outputInput,
 } from './cli/output.ts';
 import stripAnsi from 'strip-ansi';
-import { createRequire } from 'module';
-import { readFileSync } from 'fs';
-import { dirname, join } from 'path';
-import { fileURLToPath } from 'url';
-
-const require = createRequire(import.meta.url);
-let pkg;
-try {
-  pkg = require('../package.json');
-} catch (_e) {
-  // Fallback: read package.json directly
-  const __dirname = dirname(fileURLToPath(import.meta.url));
-  const pkgPath = join(__dirname, '../package.json');
-  const pkgContent = readFileSync(pkgPath, 'utf8');
-  pkg = JSON.parse(pkgContent);
-}
+import { resolve as resolvePath } from 'path';
+import { VERSION } from './version.ts';
+
+// Version comes from the shared module so that `--version`, the process log
+// and stored session records can never disagree (#285).
+const pkg = { version: VERSION };
 
 // Track if any errors occurred during execution
 let hasError = false;
@@ -226,7 +216,7 @@ async function readSystemMessages(argv) {
   let appendSystemMessage = argv['append-system-message'];
 
   if (argv['system-message-file']) {
-    const resolvedPath = require('path').resolve(
+    const resolvedPath = resolvePath(
       process.cwd(),
       argv['system-message-file']
     );
@@ -242,7 +232,7 @@ async function readSystemMessages(argv) {
   }
 
   if (argv['append-system-message-file']) {
-    const resolvedPath = require('path').resolve(
+    const resolvedPath = resolvePath(
       process.cwd(),
       argv['append-system-message-file']
     );

js/src/session/index.ts

@@ -14,6 +14,7 @@ import { SessionPrompt } from './prompt';
 import { fn } from '../util/fn';
 import { Command } from '../command';
 import { Snapshot } from '../snapshot';
+import { VERSION } from '../version';
 
 export namespace Session {
   const log = Log.create({ service: 'session' });
@@ -226,7 +227,7 @@ export namespace Session {
   }) {
     const result: Info = {
       id: Identifier.descending('session', input.id),
-      version: 'agent-cli-1.0.0',
+      version: VERSION,
       projectID: Instance.project.id,
       directory: input.directory,
       parentID: input.parentID,

js/src/session/system.ts

@@ -18,27 +18,105 @@ import PROMPT_SUMMARIZE from './prompt/summarize.txt';
 import PROMPT_TITLE from './prompt/title.txt';
 import PROMPT_CODEX from './prompt/codex.txt';
 import PROMPT_GROK_CODE from './prompt/grok-code.txt';
+import { Branding } from '../branding';
+import { Log } from '../util/log';
 
 export namespace SystemPrompt {
+  const log = Log.create({ service: 'system-prompt' });
+
   export function header(providerID: string) {
     if (providerID.includes('anthropic'))
       return [PROMPT_ANTHROPIC_SPOOF.trim()];
     return [];
   }
 
+  /** Identifiers of the selectable system prompts. */
+  export type PromptID =
+    | 'anthropic'
+    | 'anthropic-without-todo'
+    | 'beast'
+    | 'codex'
+    | 'gemini'
+    | 'grok-code'
+    | 'polaris';
+
+  const RAW: Record<PromptID, string> = {
+    anthropic: PROMPT_ANTHROPIC,
+    'anthropic-without-todo': PROMPT_ANTHROPIC_WITHOUT_TODO,
+    beast: PROMPT_BEAST,
+    codex: PROMPT_CODEX,
+    gemini: PROMPT_GEMINI,
+    'grok-code': PROMPT_GROK_CODE,
+    polaris: PROMPT_POLARIS,
+  };
+
+  /**
+   * The prompt used for any model that is not matched by an explicit rule.
+   * It is the full prompt (with todo/task-tracking discipline); models that
+   * genuinely break on todo tools must opt out explicitly via the
+   * `AGENT_SYSTEM_PROMPT` environment variable. See issue #285.
+   */
+  export const DEFAULT_PROMPT_ID: PromptID = 'anthropic';
+
+  const RULES: { matches: (modelID: string) => boolean; id: PromptID }[] = [
+    { matches: (m) => m.includes('gpt-5'), id: 'codex' },
+    {
+      matches: (m) =>
+        m.includes('gpt-') || m.includes('o1') || m.includes('o3'),
+      id: 'beast',
+    },
+    { matches: (m) => m.includes('gemini-'), id: 'gemini' },
+    { matches: (m) => m.includes('claude'), id: 'anthropic' },
+    { matches: (m) => m.includes('polaris-alpha'), id: 'polaris' },
+    { matches: (m) => m.includes('grok-code'), id: 'grok-code' },
+  ];
+
+  export function isPromptID(value: string): value is PromptID {
+    return value in RAW;
+  }
+
+  /**
+   * Resolve which prompt a model gets, and why.
+   *
+   * Resolution order:
+   * 1. explicit override via the `AGENT_SYSTEM_PROMPT` environment variable;
+   * 2. an explicit rule matching the model id;
+   * 3. {@link DEFAULT_PROMPT_ID}.
+   */
+  export function resolve(modelID: string): { id: PromptID; reason: string } {
+    const override = process.env['AGENT_SYSTEM_PROMPT']?.trim();
+    if (override) {
+      if (isPromptID(override))
+        return { id: override, reason: 'AGENT_SYSTEM_PROMPT override' };
+      log.warn(() => ({
+        message: 'unknown AGENT_SYSTEM_PROMPT value, ignoring',
+        value: override,
+        known: Object.keys(RAW),
+      }));
+    }
+    for (const rule of RULES) {
+      if (rule.matches(modelID))
+        return { id: rule.id, reason: `matched model id ${modelID}` };
+    }
+    return {
+      id: DEFAULT_PROMPT_ID,
+      reason: `default for unknown model ${modelID}`,
+    };
+  }
+
+  /** Get a prompt by id, with the product identity substituted in (#285). */
+  export function text(id: PromptID): string {
+    return Branding.apply(RAW[id]);
+  }
+
   export function provider(modelID: string) {
-    if (modelID.includes('gpt-5')) return [PROMPT_CODEX];
-    if (
-      modelID.includes('gpt-') ||
-      modelID.includes('o1') ||
-      modelID.includes('o3')
-    )
-      return [PROMPT_BEAST];
-    if (modelID.includes('gemini-')) return [PROMPT_GEMINI];
-    if (modelID.includes('claude')) return [PROMPT_ANTHROPIC];
-    if (modelID.includes('polaris-alpha')) return [PROMPT_POLARIS];
-    if (modelID.includes('grok-code')) return [PROMPT_GROK_CODE];
-    return [PROMPT_ANTHROPIC_WITHOUT_TODO];
+    const resolved = resolve(modelID);
+    log.info(() => ({
+      message: `system prompt: ${resolved.id} (${resolved.reason})`,
+      prompt: resolved.id,
+      model: modelID,
+    }));
+    return [text(resolved.id)];
   }
 
   export async function environment() {
@@ -149,18 +227,21 @@ export namespace SystemPrompt {
   export function summarize(providerID: string) {
     switch (providerID) {
       case 'anthropic':
-        return [PROMPT_ANTHROPIC_SPOOF.trim(), PROMPT_SUMMARIZE];
+        return [
+          PROMPT_ANTHROPIC_SPOOF.trim(),
+          Branding.apply(PROMPT_SUMMARIZE),
+        ];
       default:
-        return [PROMPT_SUMMARIZE];
+        return [Branding.apply(PROMPT_SUMMARIZE)];
     }
   }
 
   export function title(providerID: string) {
     switch (providerID) {
       case 'anthropic':
-        return [PROMPT_ANTHROPIC_SPOOF.trim(), PROMPT_TITLE];
+        return [PROMPT_ANTHROPIC_SPOOF.trim(), Branding.apply(PROMPT_TITLE)];
       default:
-        return [PROMPT_TITLE];
+        return [Branding.apply(PROMPT_TITLE)];
     }
   }
 }

js/src/tool/bash.ts

@@ -2,6 +2,7 @@ import z from 'zod';
 import { spawn } from 'child_process';
 import { Tool } from './tool';
 import DESCRIPTION from './bash.txt';
+import { Branding } from '../branding';
 import { Log } from '../util/log';
 import { Instance } from '../project/instance';
 import { lazy } from '../util/lazy';
@@ -53,7 +54,7 @@ const parser = lazy(async () => {
 });
 
 export const BashTool = Tool.define('bash', {
-  description: DESCRIPTION,
+  description: Branding.apply(DESCRIPTION),
   parameters: z.object({
     command: z.string().describe('The command to execute'),
     timeout: z.number().describe('Optional timeout in milliseconds').optional(),

js/src/version.ts

@@ -0,0 +1,25 @@
+/**
+ * Single source of truth for the running version.
+ *
+ * The version is read from the package manifest, so `--version`, the process
+ * log and stored session records can never disagree. See issue #285.
+ */
+import { createRequire } from 'module';
+import { readFileSync } from 'fs';
+import { dirname, join } from 'path';
+import { fileURLToPath } from 'url';
+
+function read(): string {
+  try {
+    const require = createRequire(import.meta.url);
+    return require('../package.json').version;
+  } catch {
+    // Fallback: read package.json directly (e.g. when `require` of JSON is
+    // unavailable in the current runtime configuration).
+    const here = dirname(fileURLToPath(import.meta.url));
+    return JSON.parse(readFileSync(join(here, '../package.json'), 'utf8'))
+      .version;
+  }
+}
+
+export const VERSION: string = read();