diff --git a/src/session/__tests__/fork.test.ts b/src/session/__tests__/fork.test.ts
index 49230c6..e1690b7 100644
--- a/src/session/__tests__/fork.test.ts
+++ b/src/session/__tests__/fork.test.ts
@@ -9,11 +9,12 @@ vi.mock('../../utils/logger.js', () => ({
   logger: { info: vi.fn(), warn: vi.fn(), error: vi.fn(), debug: vi.fn() },
 }));
 
-const { sendTextMock, replyInThreadMock, getThreadSessionMock, createForkedThreadSessionMock } = vi.hoisted(() => ({
+const { sendTextMock, replyInThreadMock, getThreadSessionMock, createForkedThreadSessionMock, forkClaudeSessionMock } = vi.hoisted(() => ({
   sendTextMock: vi.fn(),
   replyInThreadMock: vi.fn(),
   getThreadSessionMock: vi.fn(),
   createForkedThreadSessionMock: vi.fn(),
+  forkClaudeSessionMock: vi.fn(),
 }));
 vi.mock('../../feishu/client.js', () => ({
   feishuClient: {
@@ -27,6 +28,9 @@ vi.mock('../manager.js', () => ({
     createForkedThreadSession: createForkedThreadSessionMock,
   },
 }));
+vi.mock('../claude-session-fork.js', () => ({
+  forkClaudeSession: forkClaudeSessionMock,
+}));
 
 // config 里只用到 claude.defaultWorkDir,vi.mock 会被 hoist 到顶部,
 // 因此用 vi.hoisted 让临时目录在 mock 之前初始化。
@@ -53,6 +57,7 @@ const CHAT_ID = 'oc_chat_test';
 const USER_ID = 'ou_user_test';
 const PARENT_THREAD_ID = 'omt_parent_thread';
 const TRIGGER_MSG_ID = 'om_trigger';
+let forkCounter = 0;
 
 function makeParentSession(overrides: { workingDir?: string; conversationId?: string | null; conversationCwd?: string | null; approved?: boolean } = {}) {
   return {
@@ -77,6 +82,16 @@ function seedParentJsonl(): string {
   return path;
 }
 
+function mockOfficialForkJsonl() {
+  forkClaudeSessionMock.mockImplementation(async ({ sourceCwd }: { sourceCwd: string }) => {
+    const id = `fork-conv-id-${++forkCounter}`;
+    const path = resolveSessionJsonlPath(sourceCwd, id);
+    mkdirSync(join(path, '..'), { recursive: true });
+    writeFileSync(path, `{"sessionId":"${id}","type":"summary","summary":"official fork"}\n`);
+    return id;
+  });
+}
+
 describe('forkSession', () => {
   let parentJsonl: string;
 
@@ -85,6 +100,9 @@ describe('forkSession', () => {
     replyInThreadMock.mockReset();
     getThreadSessionMock.mockReset();
     createForkedThreadSessionMock.mockReset();
+    forkClaudeSessionMock.mockReset();
+    forkCounter = 0;
+    mockOfficialForkJsonl();
     parentJsonl = seedParentJsonl();
   });
 
@@ -94,7 +112,7 @@ describe('forkSession', () => {
     if (existsSync(dir)) rmSync(dir, { recursive: true, force: true });
   });
 
-  it('成功路径:复制 JSONL、创建话题、写入血缘字段', async () => {
+  it('成功路径:官方 fork JSONL、创建话题、写入血缘字段', async () => {
     getThreadSessionMock.mockReturnValue(makeParentSession());
     sendTextMock.mockResolvedValue('om_new_root');
     replyInThreadMock.mockResolvedValue({ messageId: 'om_reply', threadId: 'omt_new_thread' });
@@ -114,7 +132,12 @@ describe('forkSession', () => {
     expect(result.shortId).toMatch(/^[0-9a-f]{4}$/);
     expect(result.workingDir).toBe(TEST_DEFAULT_DIR);
 
-    // 新 JSONL 应已落盘
+    // SDK fork 应使用父 session/cwd,新 JSONL 应已落盘
+    expect(forkClaudeSessionMock).toHaveBeenCalledWith({
+      parentSessionId: PARENT_CONV_ID,
+      sourceCwd: TEST_DEFAULT_DIR,
+      title: expect.stringContaining(result.shortId),
+    });
     const newJsonl = resolveSessionJsonlPath(TEST_DEFAULT_DIR, result.newConversationId);
     expect(existsSync(newJsonl)).toBe(true);
 
@@ -165,9 +188,25 @@ describe('forkSession', () => {
     expect(result.ok).toBe(false);
     if (result.ok) return;
     expect(result.reason).toBe('parent_jsonl_missing');
+    expect(forkClaudeSessionMock).not.toHaveBeenCalled();
     expect(sendTextMock).not.toHaveBeenCalled();
   });
 
+  it('session_fork_failed:官方 fork 失败时不创建飞书话题', async () => {
+    getThreadSessionMock.mockReturnValue(makeParentSession());
+    forkClaudeSessionMock.mockRejectedValue(new Error('invalid transcript'));
+
+    const result = await forkSession({
+      parentThreadId: PARENT_THREAD_ID, chatId: CHAT_ID, userId: USER_ID, triggerMessageId: TRIGGER_MSG_ID,
+    });
+    expect(result.ok).toBe(false);
+    if (result.ok) return;
+    expect(result.reason).toBe('session_fork_failed');
+    expect(result.message).toContain('invalid transcript');
+    expect(sendTextMock).not.toHaveBeenCalled();
+    expect(createForkedThreadSessionMock).not.toHaveBeenCalled();
+  });
+
   it('feishu_thread_create_failed:sendText 返回 undefined,JSONL 应回滚', async () => {
     getThreadSessionMock.mockReturnValue(makeParentSession());
     sendTextMock.mockResolvedValue(undefined);
@@ -292,6 +331,9 @@ describe('forkSession - 场景 A (worktree + WIP)', () => {
     replyInThreadMock.mockReset();
     getThreadSessionMock.mockReset();
     createForkedThreadSessionMock.mockReset();
+    forkClaudeSessionMock.mockReset();
+    forkCounter = 0;
+    mockOfficialForkJsonl();
     sendTextMock.mockResolvedValue('om_new_root');
     replyInThreadMock.mockResolvedValue({ messageId: 'om_reply', threadId: 'omt_new_thread' });
 
@@ -351,8 +393,12 @@ describe('forkSession - 场景 A (worktree + WIP)', () => {
       { cwd: parentWorkdir, encoding: 'utf8' });
     expect(parentStatusAfter).toBe(parentStatusBefore);
 
-    // DB 写入的 workingDir 是新 worktree 路径
-    expect(createForkedThreadSessionMock.mock.calls[0][0].workingDir).toBe(result.workingDir);
+    // DB 写入的 workingDir/conversationCwd 是新 worktree 路径,JSONL 已移动到新 project 目录
+    const dbArgs = createForkedThreadSessionMock.mock.calls[0][0];
+    expect(dbArgs.workingDir).toBe(result.workingDir);
+    expect(dbArgs.conversationCwd).toBe(result.workingDir);
+    expect(existsSync(resolveSessionJsonlPath(result.workingDir, result.newConversationId))).toBe(true);
+    expect(existsSync(resolveSessionJsonlPath(parentWorkdir, result.newConversationId))).toBe(false);
   });
 
   it('--clean 跳过 WIP 继承:子 worktree 是纯 HEAD,无未提交改动', async () => {
diff --git a/src/session/__tests__/jsonl-fork.test.ts b/src/session/__tests__/jsonl-fork.test.ts
index 05a73e9..51da6b7 100644
--- a/src/session/__tests__/jsonl-fork.test.ts
+++ b/src/session/__tests__/jsonl-fork.test.ts
@@ -6,6 +6,7 @@ import {
   encodeProjectDir,
   resolveSessionJsonlPath,
   copyJsonlAtomic,
+  moveJsonlAtomic,
   jsonlFingerprint,
 } from '../jsonl-fork.js';
 
@@ -81,6 +82,38 @@ describe('copyJsonlAtomic', () => {
   });
 });
 
+describe('moveJsonlAtomic', () => {
+  let workDir: string;
+
+  beforeEach(() => {
+    workDir = mkdtempSync(join(tmpdir(), 'jsonl-move-test-'));
+  });
+
+  afterEach(() => {
+    rmSync(workDir, { recursive: true, force: true });
+  });
+
+  it('moves through a temp file in the target directory', () => {
+    const src = join(workDir, 'src.jsonl');
+    const dst = join(workDir, 'target', 'dst.jsonl');
+    writeFileSync(src, 'official fork');
+
+    moveJsonlAtomic(src, dst);
+
+    expect(existsSync(src)).toBe(false);
+    expect(readFileSync(dst, 'utf8')).toBe('official fork');
+  });
+
+  it('is a no-op when source and target are the same file', () => {
+    const src = join(workDir, 'same.jsonl');
+    writeFileSync(src, 'same');
+
+    moveJsonlAtomic(src, src);
+
+    expect(readFileSync(src, 'utf8')).toBe('same');
+  });
+});
+
 describe('jsonlFingerprint', () => {
   it('returns undefined for missing file', () => {
     expect(jsonlFingerprint('/nonexistent/path.jsonl')).toBeUndefined();
diff --git a/src/session/claude-session-fork.ts b/src/session/claude-session-fork.ts
new file mode 100644
index 0000000..6a403ac
--- /dev/null
+++ b/src/session/claude-session-fork.ts
@@ -0,0 +1,19 @@
+import { forkSession as forkClaudeCodeSession } from '@anthropic-ai/claude-agent-sdk';
+
+export interface ForkClaudeSessionOptions {
+  parentSessionId: string;
+  sourceCwd: string;
+  title?: string;
+}
+
+/**
+ * 用官方 Claude Code session fork 语义生成新的 transcript。
+ * 调用方仍负责把生成的 JSONL 移到目标 worktree 对应的 project 目录。
+ */
+export async function forkClaudeSession(opts: ForkClaudeSessionOptions): Promise<string> {
+  const result = await forkClaudeCodeSession(opts.parentSessionId, {
+    dir: opts.sourceCwd,
+    title: opts.title,
+  });
+  return result.sessionId;
+}
diff --git a/src/session/fork.ts b/src/session/fork.ts
index 0f17dbc..aadb33f 100644
--- a/src/session/fork.ts
+++ b/src/session/fork.ts
@@ -1,4 +1,4 @@
-import { randomBytes, randomUUID } from 'node:crypto';
+import { randomBytes } from 'node:crypto';
 import { execFileSync } from 'node:child_process';
 import { unlinkSync } from 'node:fs';
 import { resolve } from 'node:path';
@@ -6,7 +6,8 @@ import { config } from '../config.js';
 import { logger } from '../utils/logger.js';
 import { feishuClient } from '../feishu/client.js';
 import { sessionManager } from './manager.js';
-import { copyJsonlAtomic, resolveSessionJsonlPath, jsonlFingerprint } from './jsonl-fork.js';
+import { resolveSessionJsonlPath, jsonlFingerprint, moveJsonlAtomic } from './jsonl-fork.js';
+import { forkClaudeSession } from './claude-session-fork.js';
 
 /** Fork 失败的原因码（供命令层做差异化提示） */
 export type ForkFailureReason =
@@ -14,6 +15,7 @@ export type ForkFailureReason =
   | 'parent_not_found'
   | 'no_conversation'
   | 'parent_jsonl_missing'
+  | 'session_fork_failed'
   | 'feishu_thread_create_failed'
   | 'worktree_create_failed'
   | 'stash_apply_failed'
@@ -99,16 +101,16 @@ export async function forkSession(opts: ForkOptions): Promise<ForkResult | ForkE
   }
 
   const shortId = generateShortId();
-  const newConversationId = randomUUID();
+  const rootTitle = buildRootTitle(opts.description, shortId);
   // 场景 A 的子 conversationCwd 必须用新 worktree 路径(否则 SDK resume 时 cwd 不匹配)
   const newWorkdir = isScenarioA ? `${parent.workingDir}-fork-${shortId}` : parent.workingDir;
   const newConversationCwd = isScenarioA ? newWorkdir : parent.conversationCwd;
-  const newJsonl = resolveSessionJsonlPath(newConversationCwd, newConversationId);
-
   // 回滚追踪标志
   let worktreeCreated = false;
   let newBranchName: string | undefined;
-  let newJsonlCreated = false;
+  let newConversationId = '';
+  let sdkForkJsonl: string | undefined;
+  let newJsonl: string | undefined;
   let rootMessageId: string | undefined;
 
   try {
@@ -174,14 +176,29 @@ export async function forkSession(opts: ForkOptions): Promise<ForkResult | ForkE
       }
     }
 
-    // ── 通用流程: JSONL → Feishu → DB ──
-    copyJsonlAtomic(parentJsonl, newJsonl);
-    newJsonlCreated = true;
+    // ── 通用流程: 官方 transcript fork → Feishu → DB ──
+    try {
+      newConversationId = await forkClaudeSession({
+        parentSessionId: parent.conversationId,
+        sourceCwd: parent.conversationCwd,
+        title: rootTitle,
+      });
+      if (!newConversationId) {
+        throw new Error('Claude SDK did not return a forked sessionId');
+      }
+      sdkForkJsonl = resolveSessionJsonlPath(parent.conversationCwd, newConversationId);
+      newJsonl = resolveSessionJsonlPath(newConversationCwd, newConversationId);
+      moveJsonlAtomic(sdkForkJsonl, newJsonl);
+    } catch (err) {
+      throw new ForkAbort(
+        'session_fork_failed',
+        `创建 Claude 会话 fork 失败: ${(err as Error).message}`,
+      );
+    }
 
     // 在父话题里贴一条 "🔱 …" 的 top-level 消息作为新话题根。
     // 注意：reply_in_thread=true 在父消息已属于话题时会留在原话题里，所以这里直接用 sendText
     // 发到主聊天区，得到一条非话题消息；再在其上 replyInThread 形成新话题。
-    const rootTitle = buildRootTitle(opts.description, shortId);
     rootMessageId = await feishuClient.sendText(opts.chatId, rootTitle);
     if (!rootMessageId) {
       throw new ForkAbort('feishu_thread_create_failed', '创建新话题根消息失败');
@@ -243,9 +260,12 @@ export async function forkSession(opts: ForkOptions): Promise<ForkResult | ForkE
     // 父工作树状态:正常路径 push+pop 已成对完成,无需回滚;
     // 若进入 CRITICAL 分支(子 apply 成功、父 pop 失败),父 WIP 仍卡在 stash@{0},
     // 由上方 logger.error 提示用户手动 `git stash pop`,此处不再尝试。
-    if (newJsonlCreated) {
+    if (newJsonl) {
       try { unlinkSync(newJsonl); } catch { /* ignore */ }
     }
+    if (sdkForkJsonl && sdkForkJsonl !== newJsonl) {
+      try { unlinkSync(sdkForkJsonl); } catch { /* ignore */ }
+    }
     if (worktreeCreated) {
       try {
         gitExec(parent.workingDir, ['worktree', 'remove', '--force', newWorkdir]);
diff --git a/src/session/jsonl-fork.ts b/src/session/jsonl-fork.ts
index 1ef1987..d9f97aa 100644
--- a/src/session/jsonl-fork.ts
+++ b/src/session/jsonl-fork.ts
@@ -42,6 +42,23 @@ export function copyJsonlAtomic(srcPath: string, dstPath: string): void {
   }
 }
 
+/**
+ * 把 SDK 生成的 fork JSONL 放到目标 cwd 对应的 project 目录。
+ *
+ * src/dst 往往位于 ~/.claude/projects 下的不同子目录。为了避免跨设备 rename 失败，
+ * 这里先 copy 到目标目录临时文件，再 rename 成目标文件，最后删除源文件。
+ */
+export function moveJsonlAtomic(srcPath: string, dstPath: string): void {
+  if (srcPath === dstPath) {
+    if (!existsSync(srcPath)) {
+      throw new Error(`source JSONL not found: ${srcPath}`);
+    }
+    return;
+  }
+  copyJsonlAtomic(srcPath, dstPath);
+  unlinkSync(srcPath);
+}
+
 /** 计算 JSONL 末尾签名（size + mtime），P2 fork_point 字段用。 */
 export function jsonlFingerprint(jsonlPath: string): string | undefined {
   if (!existsSync(jsonlPath)) return undefined;