diff --git a/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadata.ts b/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadata.ts
index 28c14ad24..161c520d7 100644
--- a/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadata.ts
+++ b/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadata.ts
@@ -54,6 +54,7 @@ export interface ISessionMetadata {
   read(): Promise<SessionMeta>;
   update(patch: SessionMetaPatch): Promise<void>;
   setTitle(title: string): Promise<void>;
+  setGeneratedTitleIfUncustomized(title: string): Promise<boolean>;
   setArchived(archived: boolean): Promise<void>;
   registerAgent(agentId: string, meta: AgentMeta): Promise<void>;
 }
diff --git a/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadataService.ts b/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadataService.ts
index 744bc1f7e..3951239a8 100644
--- a/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadataService.ts
+++ b/packages/agent-core-v2/src/session/sessionMetadata/sessionMetadataService.ts
@@ -112,6 +112,15 @@ export class SessionMetadata extends Disposable implements ISessionMetadata {
     await this.update({ title, isCustomTitle: true });
   }
 
+  async setGeneratedTitleIfUncustomized(title: string): Promise<boolean> {
+    return this.enqueueUpdate(async () => {
+      await this.ready;
+      if (this.data.isCustomTitle === true) return false;
+      await this.applyUpdate({ title, isCustomTitle: false });
+      return true;
+    });
+  }
+
   async setArchived(archived: boolean): Promise<void> {
     await this.update({ archived });
   }
@@ -126,9 +135,12 @@ export class SessionMetadata extends Disposable implements ISessionMetadata {
     });
   }
 
-  private enqueueUpdate(work: () => Promise<void>): Promise<void> {
+  private enqueueUpdate<T>(work: () => Promise<T>): Promise<T> {
     const run = this.updateQueue.then(work, work);
-    this.updateQueue = run.catch(() => {});
+    this.updateQueue = run.then(
+      () => undefined,
+      () => undefined,
+    );
     return run;
   }
 
@@ -216,8 +228,14 @@ export function normalizeSessionMeta(raw: SessionMeta, sessionId: string): Sessi
       : undefined);
   const legacyCustomTitle =
     typeof legacy.customTitle === 'string' ? legacy.customTitle : undefined;
-  const title = legacyCustomTitle ?? raw.title;
-  const isCustomTitle = legacyCustomTitle === undefined ? raw.isCustomTitle : true;
+  const hasModernTitleState =
+    typeof raw.title === 'string' && typeof raw.isCustomTitle === 'boolean';
+  const title = hasModernTitleState ? raw.title : (legacyCustomTitle ?? raw.title);
+  const isCustomTitle = hasModernTitleState
+    ? raw.isCustomTitle
+    : legacyCustomTitle === undefined
+      ? raw.isCustomTitle
+      : true;
   if (raw.version === SESSION_META_VERSION) {
     if (cwd === raw.cwd && title === raw.title && isCustomTitle === raw.isCustomTitle) {
       return raw;
diff --git a/packages/agent-core-v2/src/session/sessionTitle/sessionTitleService.ts b/packages/agent-core-v2/src/session/sessionTitle/sessionTitleService.ts
index 2f80463e8..25d29bf8e 100644
--- a/packages/agent-core-v2/src/session/sessionTitle/sessionTitleService.ts
+++ b/packages/agent-core-v2/src/session/sessionTitle/sessionTitleService.ts
@@ -17,7 +17,7 @@
 
 import {
   KIMI_CODE_PROVIDER_NAME,
-  OAuthUnauthorizedError,
+  OAuthError,
   fetchChatTitle,
   kimiCodeToolsUrl,
   parseKimiCodeCustomHeaders,
@@ -119,7 +119,7 @@ export class SessionTitleService extends Disposable implements ISessionTitleServ
     try {
       token = await tokenProvider.getAccessToken();
     } catch (error) {
-      if (!(error instanceof OAuthUnauthorizedError)) throw error;
+      if (!(error instanceof OAuthError)) throw error;
       this.log.debug(`chat_title request unavailable: ${error.message}`);
       return undefined;
     }
@@ -139,11 +139,9 @@ export class SessionTitleService extends Disposable implements ISessionTitleServ
       this.log.debug(`chat_title request failed: ${result.message}`);
       return undefined;
     }
-    // The user may have renamed the session while the request was in flight.
-    const currentAfterRequest = await this.metadata.read();
-    if (hasCustomTitle(currentAfterRequest)) return undefined;
     const title = result.title.slice(0, MAX_GENERATED_TITLE_LENGTH);
-    await this.metadata.update({ title, isCustomTitle: false });
+    const applied = await this.metadata.setGeneratedTitleIfUncustomized(title);
+    if (!applied) return undefined;
     this.eventService.publish({
       type: 'session.meta.updated',
       payload: {
@@ -158,9 +156,13 @@ export class SessionTitleService extends Disposable implements ISessionTitleServ
 }
 
 function hasCustomTitle(metadata: {
-  readonly isCustomTitle?: boolean;
+  readonly title?: unknown;
+  readonly isCustomTitle?: unknown;
   readonly customTitle?: unknown;
 }): boolean {
+  if (typeof metadata.title === 'string' && typeof metadata.isCustomTitle === 'boolean') {
+    return metadata.isCustomTitle;
+  }
   return metadata.isCustomTitle === true || typeof metadata.customTitle === 'string';
 }
 
diff --git a/packages/agent-core-v2/test/app/sessionExport/sessionExport.test.ts b/packages/agent-core-v2/test/app/sessionExport/sessionExport.test.ts
index 7cfdab0be..bfeebba16 100644
--- a/packages/agent-core-v2/test/app/sessionExport/sessionExport.test.ts
+++ b/packages/agent-core-v2/test/app/sessionExport/sessionExport.test.ts
@@ -999,6 +999,7 @@ function stubSessionMetadata(meta: SessionMeta): ISessionMetadata {
     read: async () => meta,
     update: async () => {},
     setTitle: async () => {},
+    setGeneratedTitleIfUncustomized: async () => false,
     setArchived: async () => {},
     registerAgent: async () => {},
   };
diff --git a/packages/agent-core-v2/test/app/sessionLifecycle/sessionLifecycle.test.ts b/packages/agent-core-v2/test/app/sessionLifecycle/sessionLifecycle.test.ts
index 40766015e..eca1bd241 100644
--- a/packages/agent-core-v2/test/app/sessionLifecycle/sessionLifecycle.test.ts
+++ b/packages/agent-core-v2/test/app/sessionLifecycle/sessionLifecycle.test.ts
@@ -107,6 +107,7 @@ function metadataStub(): ISessionMetadata {
     read: () => Promise.resolve({} as never),
     update: () => Promise.resolve(),
     setTitle: () => Promise.resolve(),
+    setGeneratedTitleIfUncustomized: () => Promise.resolve(false),
     setArchived: () => Promise.resolve(),
     registerAgent: () => Promise.resolve(),
   };
diff --git a/packages/agent-core-v2/test/session/sessionMetadata/sessionMetadata.test.ts b/packages/agent-core-v2/test/session/sessionMetadata/sessionMetadata.test.ts
index 28060aa74..a4ed327be 100644
--- a/packages/agent-core-v2/test/session/sessionMetadata/sessionMetadata.test.ts
+++ b/packages/agent-core-v2/test/session/sessionMetadata/sessionMetadata.test.ts
@@ -1,4 +1,4 @@
-import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
 import { SyncDescriptor } from '#/_base/di/descriptors';
 import { DisposableStore } from '#/_base/di/lifecycle';
@@ -60,7 +60,10 @@ describe('SessionMetadata', () => {
     ix.set(ISessionMetadata, new SyncDescriptor(SessionMetadata));
   });
 
-  afterEach(() => { disposables.dispose(); });
+  afterEach(() => {
+    disposables.dispose();
+    vi.restoreAllMocks();
+  });
 
   it('creates an initial document on first read', async () => {
     const meta = ix.get(ISessionMetadata);
@@ -93,6 +96,16 @@ describe('SessionMetadata', () => {
     expect(await meta.read()).toMatchObject({ title: 't', archived: true });
   });
 
+  it('sets a generated title while the metadata remains uncustomized', async () => {
+    const meta = ix.get(ISessionMetadata);
+
+    await expect(meta.setGeneratedTitleIfUncustomized('generated title')).resolves.toBe(true);
+    await expect(meta.read()).resolves.toMatchObject({
+      title: 'generated title',
+      isCustomTitle: false,
+    });
+  });
+
   it('persists across instances', async () => {
     const meta = ix.get(ISessionMetadata);
     await meta.update({ title: 'persisted' });
@@ -149,7 +162,7 @@ describe('SessionMetadata', () => {
     });
   });
 
-  it('preserves a legacy customTitle when title is also present', async () => {
+  it('trusts modern custom title state over a stale legacy customTitle', async () => {
     const store = ix.get(IAtomicDocumentStore);
     await store.set(META_SCOPE, 'state.json', {
       id: 's1',
@@ -157,25 +170,64 @@ describe('SessionMetadata', () => {
       createdAt: 1700000000000,
       updatedAt: 1700000000000,
       archived: false,
-      title: 'base title',
+      title: 'renamed title',
+      isCustomTitle: true,
       customTitle: 'legacy custom title',
     });
 
     const meta = ix.get(ISessionMetadata);
     await expect(meta.read()).resolves.toMatchObject({
-      title: 'legacy custom title',
+      title: 'renamed title',
       isCustomTitle: true,
     });
 
     await meta.update({ archived: true });
     const fresh = createFreshMetadata(ix);
     await expect(fresh.read()).resolves.toMatchObject({
-      title: 'legacy custom title',
+      title: 'renamed title',
       isCustomTitle: true,
       archived: true,
     });
   });
 
+  it('keeps a queued custom title when a generated title is enqueued afterward', async () => {
+    const meta = ix.get(ISessionMetadata);
+    await meta.ready;
+    const store = ix.get(IAtomicDocumentStore);
+    const set = store.set.bind(store);
+    let releaseWrite: (() => void) | undefined;
+    let markWriteStarted: (() => void) | undefined;
+    const writeStarted = new Promise<void>((resolve) => {
+      markWriteStarted = resolve;
+    });
+    const writeReleased = new Promise<void>((resolve) => {
+      releaseWrite = resolve;
+    });
+    let shouldBlock = true;
+    vi.spyOn(store, 'set').mockImplementation(async (scope, key, value) => {
+      if (shouldBlock) {
+        shouldBlock = false;
+        markWriteStarted?.();
+        await writeReleased;
+      }
+      await set(scope, key, value);
+    });
+
+    const priorWrite = meta.update({ lastPrompt: 'hello' });
+    await writeStarted;
+    const rename = meta.setTitle('user title');
+    const generated = meta.setGeneratedTitleIfUncustomized('generated title');
+    releaseWrite?.();
+
+    await priorWrite;
+    await rename;
+    await expect(generated).resolves.toBe(false);
+    await expect(meta.read()).resolves.toMatchObject({
+      title: 'user title',
+      isCustomTitle: true,
+    });
+  });
+
   it('leaves existing agents/custom maps untouched', async () => {
     const store = ix.get(IAtomicDocumentStore);
     await store.set(META_SCOPE, 'state.json', {
diff --git a/packages/agent-core-v2/test/session/sessionTitle/sessionTitleService.test.ts b/packages/agent-core-v2/test/session/sessionTitle/sessionTitleService.test.ts
index 40af63f59..1b7cfc039 100644
--- a/packages/agent-core-v2/test/session/sessionTitle/sessionTitleService.test.ts
+++ b/packages/agent-core-v2/test/session/sessionTitle/sessionTitleService.test.ts
@@ -5,7 +5,7 @@
 
 import { afterEach, beforeEach, describe, expect, it, vi, type Mock } from 'vitest';
 
-import { OAuthUnauthorizedError } from '@moonshot-ai/kimi-code-oauth';
+import { OAuthConnectionError, OAuthUnauthorizedError } from '@moonshot-ai/kimi-code-oauth';
 
 import { DisposableStore, type IDisposable } from '#/_base/di/lifecycle';
 import { createServices, type TestInstantiationService } from '#/_base/di/test';
@@ -88,6 +88,12 @@ class FakeSessionMetadata implements ISessionMetadata {
     return this.update({ title, isCustomTitle: true });
   }
 
+  async setGeneratedTitleIfUncustomized(title: string): Promise<boolean> {
+    if (this.meta.isCustomTitle === true) return false;
+    await this.update({ title, isCustomTitle: false });
+    return true;
+  }
+
   setArchived(archived: boolean): Promise<void> {
     return this.update({ archived });
   }
@@ -168,7 +174,6 @@ describe('SessionTitleService', () => {
         reg.define(ISessionTitleService, SessionTitleService);
       },
     });
-    // Construct the SUT so its bus subscription is live.
     ix.get(ISessionTitleService);
   });
 
@@ -300,6 +305,24 @@ describe('SessionTitleService', () => {
     expect(fetchMock).not.toHaveBeenCalled();
   });
 
+  it('returns unavailable when OAuth token retrieval has an operational failure', async () => {
+    tokenError = new OAuthConnectionError('connection failed');
+    await metadata.update({ lastPrompt: 'hello' });
+
+    await expect(ix.get(ISessionTitleService).generateTitle()).resolves.toBeUndefined();
+    expect(fetchMock).not.toHaveBeenCalled();
+  });
+
+  it('propagates unexpected token provider failures', async () => {
+    tokenError = new Error('unexpected failure');
+    await metadata.update({ lastPrompt: 'hello' });
+
+    await expect(ix.get(ISessionTitleService).generateTitle()).rejects.toThrow(
+      'unexpected failure',
+    );
+    expect(fetchMock).not.toHaveBeenCalled();
+  });
+
   it('includes environment custom headers', async () => {
     vi.stubEnv('KIMI_CODE_CUSTOM_HEADERS', 'X-Proxy-Header: from-env\n');
     await metadata.update({ lastPrompt: 'hello' });
@@ -338,6 +361,19 @@ describe('SessionTitleService', () => {
     expect(fetchMock).not.toHaveBeenCalled();
   });
 
+  it('trusts a modern non-custom title over a stale legacy customTitle', async () => {
+    metadata.meta = {
+      ...metadata.meta,
+      title: 'easy title',
+      isCustomTitle: false,
+      lastPrompt: 'hello',
+      customTitle: 'stale legacy title',
+    } as SessionMeta;
+
+    await expect(ix.get(ISessionTitleService).generateTitle()).resolves.toBe('生成的标题');
+    expect(metadata.meta.title).toBe('生成的标题');
+  });
+
   it('shares an in-flight generation between automatic and manual requests', async () => {
     let resolveFetch: ((response: Response) => void) | undefined;
     fetchMock.mockImplementationOnce(
diff --git a/packages/agent-core-v2/test/tool/tool.test.ts b/packages/agent-core-v2/test/tool/tool.test.ts
index fa98629ac..ca7df7c49 100644
--- a/packages/agent-core-v2/test/tool/tool.test.ts
+++ b/packages/agent-core-v2/test/tool/tool.test.ts
@@ -424,6 +424,7 @@ function sessionMetadataStub(agents: Readonly<Record<string, AgentMeta>>): ISess
     }),
     update: async () => {},
     setTitle: async () => {},
+    setGeneratedTitleIfUncustomized: async () => false,
     setArchived: async () => {},
     registerAgent: async () => {},
   };
diff --git a/packages/agent-core/src/session/rpc.ts b/packages/agent-core/src/session/rpc.ts
index ff52c0356..4a704ee9b 100644
--- a/packages/agent-core/src/session/rpc.ts
+++ b/packages/agent-core/src/session/rpc.ts
@@ -394,6 +394,11 @@ function isUntitled(title: unknown): boolean {
 }
 
 function hasCustomTitle(metadata: SessionMeta): boolean {
-  if (metadata.isCustomTitle) return true;
-  return typeof (metadata as SessionMeta & { customTitle?: unknown }).customTitle === 'string';
+  if (typeof metadata.title === 'string' && typeof metadata.isCustomTitle === 'boolean') {
+    return metadata.isCustomTitle;
+  }
+  return (
+    metadata.isCustomTitle ||
+    typeof (metadata as SessionMeta & { customTitle?: unknown }).customTitle === 'string'
+  );
 }
diff --git a/packages/agent-core/test/session/prompt-metadata.test.ts b/packages/agent-core/test/session/prompt-metadata.test.ts
index dccbd1c3e..d3ef3b58c 100644
--- a/packages/agent-core/test/session/prompt-metadata.test.ts
+++ b/packages/agent-core/test/session/prompt-metadata.test.ts
@@ -147,6 +147,31 @@ describe('SessionAPIImpl auto title', () => {
     expect(titleEvents.at(-1)).toMatchObject({ title: '生成的标题' });
   });
 
+  it('trusts modern non-custom title state over a stale legacy customTitle', async () => {
+    stubChatTitleFetch('生成的标题');
+    const { api, session, events, agent } = await setupAutoTitleSession({
+      autoTitle: true,
+    });
+    session.metadata = {
+      ...session.metadata,
+      title: 'New Session',
+      isCustomTitle: false,
+      customTitle: 'stale legacy title',
+    } as typeof session.metadata;
+
+    await api.prompt({ agentId: 'main', input: [{ type: 'text', text: '帮我看个 Go 报错' }] });
+    if (agent.turn.hasActiveTurn) {
+      await agent.turn.waitForCurrentTurn();
+    }
+
+    await waitFor(() =>
+      events.some((event) =>
+        event['type'] === 'session.meta.updated' && event['title'] === '生成的标题'
+      ),
+    );
+    expect(session.metadata.title).toBe('生成的标题');
+  });
+
   it('sends managed request headers with the established layer precedence', async () => {
     vi.stubEnv(
       'KIMI_CODE_CUSTOM_HEADERS',
diff --git a/packages/oauth/src/managed-tools.ts b/packages/oauth/src/managed-tools.ts
index 546e7faa6..c859239c8 100644
--- a/packages/oauth/src/managed-tools.ts
+++ b/packages/oauth/src/managed-tools.ts
@@ -41,14 +41,13 @@ export async function fetchChatTitle(
     controller.abort();
   }, opts.timeoutMs ?? 8000);
   try {
+    const headers = new Headers(opts.headers);
+    headers.set('Authorization', `Bearer ${accessToken}`);
+    headers.set('Accept', 'application/json');
+    headers.set('Content-Type', 'application/json');
     const res = await fetch(url, {
       method: 'POST',
-      headers: {
-        ...opts.headers,
-        Authorization: `Bearer ${accessToken}`,
-        Accept: 'application/json',
-        'Content-Type': 'application/json',
-      },
+      headers,
       body: JSON.stringify({
         method: 'chat_title',
         params: { chat_content: chatContent },
diff --git a/packages/oauth/test/managed-tools.test.ts b/packages/oauth/test/managed-tools.test.ts
index ea5d71166..fd7429603 100644
--- a/packages/oauth/test/managed-tools.test.ts
+++ b/packages/oauth/test/managed-tools.test.ts
@@ -60,7 +60,7 @@ describe('fetchChatTitle', () => {
     });
   });
 
-  it('keeps protocol headers authoritative when custom headers collide', async () => {
+  it('keeps protocol headers authoritative when custom header casing differs', async () => {
     const fetchMock = vi.fn(
       async () =>
         new Response(JSON.stringify({ title: '标题' }), {
@@ -72,9 +72,9 @@ describe('fetchChatTitle', () => {
 
     await fetchChatTitle('https://api.example/tools', 'access-token', 'user: hi', {
       headers: {
-        Authorization: 'Bearer wrong-token',
-        Accept: 'text/plain',
-        'Content-Type': 'text/plain',
+        authorization: 'Bearer wrong-token',
+        aCcEpT: 'text/plain',
+        'content-TYPE': 'text/plain',
         'X-Proxy-Header': 'present',
       },
     });