[Critical] supportedLanguages is added to the response object but the CapabilitiesEnvelope interface in packages/cli/src/serve/types.ts was not updated. This causes a TypeScript build error (TS2353: Object literal may only specify known properties).

Add supportedLanguages?: string[] to the CapabilitiesEnvelope interface in types.ts (after the policy field, around line 234):

  /**
   * Language codes supported by this daemon. Additive — older
   * daemons omit this field. Clients should treat absence as
   * "unknown" rather than "none".
   */
  supportedLanguages?: string[];

— qwen3.7-plus via Qwen Code /review

Fixed — added supportedLanguages?: string[] to CapabilitiesEnvelope in types.ts.

[Suggestion] Unlike languageCommand.ts (lines 129-134) and acpAgent.ts (lines 2938-2942), this caller does not register the path via setOutputLanguageFilePath after the first-time write. When config.getOutputLanguageFilePath() returns undefined (no file existed at startup), the file is correctly written to the global default, but config.outputLanguageFilePath stays undefined for the session's lifetime.

This means subsequent reads via config.getOutputLanguageFilePath() (e.g., in side queries) continue to return undefined until the daemon restarts and Config is re-constructed.

— qwen3.7-plus via Qwen Code /review

Fixed — extracted writeOutputLanguageAndRegisterPath() helper in languageUtils.ts, all 3 call sites (acpAgent, languageCommand, SettingsDialog) now include the registration step.

[Suggestion] In the multi-session refresh loop, if updateOutputLanguageFile throws for any session (e.g., EACCES on a project-level .qwen/ directory), the subsequent refreshHierarchicalMemory() and refreshSystemInstruction() calls are skipped for that session — leaving it with a stale system instruction.

Consider wrapping the file writes in a try/catch so the refresh calls always execute:

allSessions.map(async (s) => {
  const cfg = s.getConfig();
  const sessionPath = cfg.getOutputLanguageFilePath();
  try {
    if (sessionPath && sessionPath !== writtenPath) {
      updateOutputLanguageFile(settingValue, sessionPath);
    }
    if (!sessionPath) {
      const fallback = getOutputLanguageFilePath();
      updateOutputLanguageFile(settingValue, fallback);
      cfg.setOutputLanguageFilePath(fallback);
    }
  } catch (err) {
    debugLogger.warn('Failed to write output-language.md for session:', err);
  }
  await cfg.refreshHierarchicalMemory();
  await cfg.getGeminiClient()?.refreshSystemInstruction();
}),

Additionally, when multiple sessions share the same path (e.g., all undefined → global default), the same file is written N times with identical content. A Set<string> of already-written paths would avoid the redundant I/O.

— qwen3.7-plus via Qwen Code /review

Fixed — wrapped file writes in try/catch so refreshHierarchicalMemory() and refreshSystemInstruction() always execute. Skipped Set<string> dedup (1-3 sessions, negligible I/O).

[Suggestion] The three-step sequence here — get targetPath from config, call updateOutputLanguageFile(settingValue, targetPath), then register the global fallback via setOutputLanguageFilePath() when targetPath is undefined — is copy-pasted identically in languageCommand.ts:128-134, and partially (missing the registration step) in SettingsDialog.tsx:382.

This duplication has already produced a concrete bug within this PR: SettingsDialog.tsx omits the registration step, so when getOutputLanguageFilePath() returns undefined, the global path is never registered on the config. Any future call site that omits or misorders a step will silently break language switching.

Consider extracting a helper in languageUtils.ts that encapsulates the full sequence:

export function writeOutputLanguageAndRegisterPath(
  settingValue: string,
  config: {
    getOutputLanguageFilePath(): string | undefined;
    setOutputLanguageFilePath(p: string): void;
  },
): void {
  const targetPath = config.getOutputLanguageFilePath();
  updateOutputLanguageFile(settingValue, targetPath);
  if (!targetPath) {
    config.setOutputLanguageFilePath(getOutputLanguageFilePath());
  }
}

Then replace the three inline copies with a single call each.

— qwen3.7-max via Qwen Code /review

Done — writeOutputLanguageAndRegisterPath() in languageUtils.ts replaces all 3 inline copies. This also fixed the SettingsDialog bug (comment #2) as a side effect.

[Critical] The inner try/catch around file writes swallows errors before allSettled sees them, so failedCount only tracks refreshHierarchicalMemory() / refreshSystemInstruction() failures. The refreshed flag will be true even when every other session's output-language.md write failed silently (permission denied, disk full).

On session restart, those sessions will revert to the previous language with no user-visible error.

Suggestion: Let the file-write error propagate (remove the inner try/catch) so allSettled captures it as a rejection, or track write failures separately:

let fileWriteFailed = false;
try {
  const sessionPath = cfg.getOutputLanguageFilePath();
  if (sessionPath && sessionPath !== writtenPath) {
    updateOutputLanguageFile(settingValue, sessionPath);
  }
  if (!sessionPath) {
    cfg.setOutputLanguageFilePath(getOutputLanguageFilePath());
  }
} catch (err) {
  fileWriteFailed = true;
  debugLogger.warn('Failed to write output-language.md for session:', err);
}
await cfg.refreshHierarchicalMemory();
await cfg.getGeminiClient()?.refreshSystemInstruction();
// ...
refreshed = results.length === 0 || (failedCount === 0 && !fileWriteFailed);

Also, when !sessionPath, writeOutputLanguageAndRegisterPath(settingValue, cfg) writes to the global default path which was already written above (identical to writtenPath). Only the registration side-effect (cfg.setOutputLanguageFilePath(...)) is needed — the write is redundant.

Fixed in ec3b541:

1. Removed inner try/catch — write errors now propagate to allSettled, making failedCount and refreshed accurate.
2. For !sessionPath case: only register the path (cfg.setOutputLanguageFilePath(...)) — the global file was already written, so the write was indeed redundant.

[Medium] The mock provides setOutputLanguageFilePath: vi.fn() (here and at lines 467, 510), but no test asserts that setOutputLanguageFilePath was actually called with the expected argument.

The path-registration side-effect (cfg.setOutputLanguageFilePath(getOutputLanguageFilePath())) is the key new behavior of writeOutputLanguageAndRegisterPath. Without an assertion like:

expect(config.setOutputLanguageFilePath).toHaveBeenCalledWith(
  expect.any(String),
);

…a future refactor could silently drop the registration call and tests would still pass. Consider adding this assertion to at least one test case that exercises the write-and-register path.

Added assertion in the "should save LLM output language setting" test that setOutputLanguageFilePath is called with a string when getOutputLanguageFilePath returns undefined.

[Critical] When the initiating session has a project-level outputLanguageFilePath (e.g. <cwd>/.qwen/output-language.md), writtenPath is that project path. But sessions without a path are registered to getOutputLanguageFilePath() (the global default ~/.qwen/output-language.md) — a file that was never written. Their refreshHierarchicalMemory() then reads stale content.

Fix: use writtenPath so the session points to the file that was actually written:

— qwen3.7-plus via Qwen Code /review

Fixed — restored writeOutputLanguageAndRegisterPath(settingValue, cfg) for !sessionPath sessions. When writtenPath is a project path, the global file was indeed never written, so we need the write here (not just registration).

[Suggestion] Commit ec3b541 removed the inner try/catch so write errors propagate to allSettled — but this means a write failure (EACCES, ENOSPC) throws out of the entire callback, skipping refreshHierarchicalMemory() and refreshSystemInstruction() for that session. The R1 reply said "wrapped file writes in try/catch so refresh always runs" but the actual code does the opposite.

Wrap only the write in try/catch so the refresh always executes:

const cfg = s.getConfig();
const sessionPath = cfg.getOutputLanguageFilePath();
try {
  if (sessionPath && sessionPath !== writtenPath) {
    updateOutputLanguageFile(settingValue, sessionPath);
  }
} catch (err) {
  debugLogger.warn(`Failed to write output-language.md for session:`, err);
}
if (!sessionPath) {
  cfg.setOutputLanguageFilePath(writtenPath);
}
await cfg.refreshHierarchicalMemory();
await cfg.getGeminiClient()?.refreshSystemInstruction();

— qwen3.7-plus via Qwen Code /review

Fixed — restored try/catch around file writes only, so refreshHierarchicalMemory() and refreshSystemInstruction() always execute regardless of write outcome.

[Suggestion] This cast triggers two tsc errors:

• TS2352: Conversion of type 'Config | null' to type 'Record<string, unknown>' may be a mistake
• TS4111: Property 'setOutputLanguageFilePath' comes from an index signature, so it must be accessed with ['setOutputLanguageFilePath']

Fix: use bracket notation with a double cast, or type the mock more precisely:

— qwen3.7-plus via Qwen Code /review

Fixed — switched to double cast (as unknown as Record<string, unknown>) with bracket notation.

[Suggestion] The multi-session fan-out loop (lines 5542–5571) is the most complex new logic in this PR — three branching conditions handle different outputLanguageFilePath scenarios across sessions — but has no test coverage. A future refactor of the path comparison, write/refresh ordering, or writtenPath computation could silently break multi-session language propagation without any test catching it.

Consider adding a test that creates multiple mock sessions with varying getOutputLanguageFilePath() return values (project path, undefined, same as originating), triggers the language ext-method with syncOutputLanguage: true, and asserts:

1. Files are written to correct paths
2. setOutputLanguageFilePath is called on sessions with no path
3. refreshHierarchicalMemory is called on every session

— qwen3.7-max via Qwen Code /review

Agreed this loop deserves dedicated test coverage. Filing as a follow-up — the multi-session fan-out requires mocking QwenAgent + multiple Session instances with varying Config, which is a meaningful test infrastructure addition beyond this bug fix scope.

Added in 250b50b — test covers 3 session scenarios (project path / different project path / no path) and asserts file writes, path registration, and refresh calls for each.

[Suggestion] The error log here ('Failed to write output-language.md for session:') omits the session ID and target file path. When multiple sessions fail writes concurrently, the logs are indistinguishable — an operator cannot tell which session or which .qwen/ directory failed.

The same applies to the initiator's log at line 5526.

— qwen3.7-max via Qwen Code /review

Good catch — 已在日志中加入 session ID 和目标路径，方便排查多 session 并发写入失败的场景。

[Critical] SetSessionLanguageResult is added to the daemon barrel export here, but is not re-exported from the top-level SDK barrel at packages/sdk-typescript/src/index.ts. Peer types like SetModelResult (line 168 of src/index.ts) are properly re-exported. This means SDK consumers importing from @qwen-code/sdk cannot use the return type of setSessionLanguage().

Fix: Add type SetSessionLanguageResult to the export list in packages/sdk-typescript/src/index.ts, alongside the existing SetModelResult and SessionMetadataResult exports.

— qwen3.7-max via Qwen Code /review

确实漏了，已在 packages/sdk-typescript/src/index.ts 中补上 type SetSessionLanguageResult 的 re-export，与 SetModelResult 同级。

[Suggestion] Lines 5475-5478 compute [...SUPPORTED_LANGUAGES.map((l) => l.code), 'auto'] inline, duplicating the identical expression hoisted as LANGUAGE_CODES in server.ts:971. If a new language code is added to one site but not the other, the ACP and HTTP endpoints will silently disagree on what is valid.

Extract a single shared constant (e.g., export LANGUAGE_CODES from i18n/index.ts or languageUtils.ts) and import it in both server.ts and acpAgent.ts.

— qwen3.7-max via Qwen Code /review

认同重复计算的问题。不过提取共享常量属于跨模块重构（server.ts 在 serve 层，acpAgent 在 ACP 层），放到 follow-up 更合适，避免本 PR 范围扩大。

[Suggestion] writeOutputLanguageAndRegisterPath — the core fix function — has no direct unit tests in languageUtils.test.ts. The only coverage comes from acpAgent.test.ts where it is fully mocked, so the real implementation is never exercised.

Key untested behaviors:

• Writes to config.getOutputLanguageFilePath() when it returns a path
• Falls back to the global path when config path is undefined
• Calls setOutputLanguageFilePath with the global path only on first creation
• Handles null/undefined config gracefully

Add a describe('writeOutputLanguageAndRegisterPath') block covering these cases, plus a test for writeOutputLanguageFile(language, targetPath) verifying the custom path is used.

— qwen3.7-max via Qwen Code /review

已在 languageUtils.test.ts 中新增 4 个直接测试：config-bound 路径写入、undefined 回退 + 注册、null config、undefined config。覆盖了核心修复函数的关键分支。

[Critical] sessionPath is declared with const inside the try block (line 5554) but referenced here in the catch block. These are separate block scopes — sessionPath is not visible in catch.

Impact:

1. TypeScript compilation error — TS2304: Cannot find name 'sessionPath' (confirmed with tsc --noEmit --strict).
2. Runtime ReferenceError: sessionPath is not defined — if cfg.getOutputLanguageFilePath() throws, the catch block will throw a second error that masks the original, making debugging harder.

Suggested fix: Declare sessionPath before the try block so it is accessible in both try and catch:

let sessionPath: string | undefined;
try {
  sessionPath = cfg.getOutputLanguageFilePath();
  if (sessionPath && sessionPath !== writtenPath) {
    updateOutputLanguageFile(settingValue, sessionPath);
  }
  if (!sessionPath) {
    writeOutputLanguageAndRegisterPath(settingValue, cfg);
  }
} catch (err) {
  debugLogger.warn(
    `Failed to write output-language.md for session ${s.getId()} (path=${sessionPath ?? 'global-default'}):`,
    err,
  );
}

— automated review (qwen-code)

好眼力，确实是块作用域 bug。已将 const sessionPath 提到 try 外改为 let sessionPath: string | undefined，catch 中可以正常访问了。

[Critical] sessionPath is declared with const inside the try block (line 5554), but is referenced here in the catch block. Since const is block-scoped, this is a TypeScript compile error (TS2304: Cannot find name 'sessionPath'). At runtime, the catch block would throw a ReferenceError, masking the original file-write error and skipping refreshHierarchicalMemory() / refreshSystemInstruction() for that session.

— qwen3.7-max via Qwen Code /review

已在上一个 commit (47217b9) 中修复了这个问题，const 已改为 let 并提升到 try 外。

[Suggestion] The multi-session fan-out test only covers the happy path where all writes succeed. The catch branch in the fan-out loop is never exercised — which is exactly why the sessionPath scoping bug (see comment on acpAgent.ts:5563) was not caught by tests.

Consider adding a test where one session's getOutputLanguageFilePath() throws, verifying that:

• The error is caught and logged without crashing the callback
• Other sessions' writes and refreshes still execute
• refreshHierarchicalMemory() / refreshSystemInstruction() still run for the failed session

— qwen3.7-max via Qwen Code /review

已添加 catch 分支测试 — 模拟一个 session 的 updateOutputLanguageFile 抛 EACCES，验证该 session 的 refreshHierarchicalMemory 和 refreshSystemInstruction 仍然被调用。

[Suggestion] writeOutputLanguageFile and updateOutputLanguageFile both gained a new optional targetPath parameter, but no test passes a targetPath argument. The fan-out logic in acpAgent.ts depends on updateOutputLanguageFile(settingValue, sessionPath) writing to the correct path — this dependency is untested.

Suggested tests:

it('writes to targetPath when provided', () => {
  writeOutputLanguageFile('Chinese', '/custom/.qwen/output-language.md');
  expect(fs.writeFileSync).toHaveBeenCalledWith(
    '/custom/.qwen/output-language.md',
    expect.stringContaining('Chinese'),
    'utf-8',
  );
});

it('forwards targetPath to writeOutputLanguageFile', () => {
  updateOutputLanguageFile('French', '/proj/.qwen/output-language.md');
  expect(fs.writeFileSync).toHaveBeenCalledWith(
    '/proj/.qwen/output-language.md',
    expect.stringContaining('French'),
    'utf-8',
  );
});