diff --git a/.trellis/tasks/09-27-codex-start-lock-retry/check.jsonl b/.trellis/tasks/09-27-codex-start-lock-retry/check.jsonl
new file mode 100644
index 0000000..99f482c
--- /dev/null
+++ b/.trellis/tasks/09-27-codex-start-lock-retry/check.jsonl
@@ -0,0 +1,3 @@
+{"file":".trellis/spec/backend/error-handling.md","reason":"检查启动忙错误、非暂时错误与最终错误信息是否符合后端错误处理规范。"}
+{"file":".trellis/spec/backend/logging-guidelines.md","reason":"检查锁竞争和退避日志是否脱敏、可追踪且不过度输出。"}
+{"file":".trellis/spec/backend/quality-guidelines.md","reason":"检查实现和回归测试是否满足后端质量要求。"}
diff --git a/.trellis/tasks/09-27-codex-start-lock-retry/implement.jsonl b/.trellis/tasks/09-27-codex-start-lock-retry/implement.jsonl
new file mode 100644
index 0000000..afbbb78
--- /dev/null
+++ b/.trellis/tasks/09-27-codex-start-lock-retry/implement.jsonl
@@ -0,0 +1,3 @@
+{"file":".trellis/spec/backend/error-handling.md","reason":"启动失败、可重试错误与最终错误诊断需要遵循后端错误处理约定。"}
+{"file":".trellis/spec/backend/logging-guidelines.md","reason":"锁等待、重试与释放需要遵循现有日志脱敏和事件命名约定。"}
+{"file":".trellis/spec/backend/quality-guidelines.md","reason":"新增跨进程锁与测试需要遵循后端质量和验证要求。"}
diff --git a/.trellis/tasks/09-27-codex-start-lock-retry/prd.md b/.trellis/tasks/09-27-codex-start-lock-retry/prd.md
new file mode 100644
index 0000000..1f3cc11
--- /dev/null
+++ b/.trellis/tasks/09-27-codex-start-lock-retry/prd.md
@@ -0,0 +1,35 @@
+# Codex 启动单实例锁与退避重试
+
+## 目标
+
+避免 cc-web 启动 Codex app-server 时与其他 cc-web 实例或残留启动流程并发写入同一 `CODEX_HOME`，导致 SQLite 报 `database is locked` 并直接启动失败。
+
+## 范围
+
+- 在 `lib/codex-app-server-client.js` 的 app-server 启动层实现跨进程单实例锁。
+- 锁文件固定为 `<CODEX_HOME>/.cc-web-codex.lock`；锁目录按解析后的绝对 `CODEX_HOME` 隔离。
+- 锁持有范围从启动尝试前开始，覆盖 app-server 初始化成功后的整个子进程生命周期；仅在子进程收到 `exit`/`error`、初始化失败清理完成或显式 `stop()` 后释放。
+- 锁记录使用 JSON，至少包含 `pid`、Linux `/proc/<pid>/stat` 的进程启动时间（无法读取时为 `null`）、随机 `token`、创建时间。释放前必须校验 token，避免误删后来者的锁。
+- 陈旧锁判定：PID 不存在，或 PID 存在但进程启动时间与记录不一致；记录损坏或不完整时，先按活动锁保护，超过 2 秒宽限期仍未补全才允许清理。
+- 锁获取默认最多等待 30 秒，轮询间隔 200ms 起步、最多 2 秒并加入少量随机抖动；等待超时返回 `CODEX_HOME_LOCK_BUSY`，不杀死锁持有者。
+- 对可判定为 SQLite/状态库暂时忙的初始化失败执行最多 4 次启动尝试，延迟为 500ms、1s、2s（上限 5s）并加入少量随机抖动；每次重试都等待旧子进程退出、释放本次锁后重新获取锁。默认总等待不超过 30 秒（不包含一次 30 秒初始化 RPC 超时）。
+- 可通过环境变量覆盖：`CC_WEB_CODEX_LOCK_WAIT_MS`、`CC_WEB_CODEX_START_RETRY_ATTEMPTS`、`CC_WEB_CODEX_START_RETRY_DELAY_MS`、`CC_WEB_CODEX_START_RETRY_MAX_DELAY_MS`；所有值限制在合理范围内。
+- 仅当 stderr、启动错误 message 或错误 cause 明确包含以下模式时重试：`database is locked`、`database table is locked`、`SQLITE_BUSY`、`SQLITE_BUSY_TIMEOUT`、`failed to open ... (state|log|database)`、`failed to initialize state runtime`。不因鉴权、命令不存在、参数错误、协议错误或普通网络错误重试。
+- 保留现有 app-server 客户端 API 与 worker/source 两条启动路径。
+- 增加可独立运行的 Node 回归测试，覆盖锁互斥、活动锁等待超时、陈旧锁清理、PID 启动时间不匹配保护、暂时性错误重试、非暂时错误不重试、成功/失败/显式停止后的锁释放。
+
+## 约束
+
+- 不删除用户数据，不改动用户的 Codex 数据库；只创建/清理 cc-web 自己的锁文件。
+- 不把外部 Codex 进程误判为可安全杀死的残留进程；锁竞争只等待或报错。
+- `SIGKILL` 等无法执行清理的场景依赖 PID + 启动时间识别陈旧锁，不保证实时删除锁文件。
+- 启动失败最终抛出的错误保留最后一次原始 stderr，并附带尝试次数、锁路径和最后一次退避原因；日志不写入 API key。
+- 重试仅发生在 `initialize` 阶段，不能自动重发 `thread/start`、`turn/start` 或其他有副作用的请求。
+
+## 完成标准
+
+1. 同一 `CODEX_HOME` 的两个 cc-web app-server 客户端不能同时持有锁；第二个客户端在锁释放前最多等待配置的锁等待时长，超时得到 `CODEX_HOME_LOCK_BUSY` 和锁持有者摘要。
+2. 初始化 stderr/message 命中暂时性 SQLite 模式时，按明确的有限退避策略重新启动，成功后对调用方透明；非暂时性错误只尝试一次。
+3. app-server 正常停止、初始化失败和进程退出都会释放锁；无存活 PID 或 PID 启动时间不匹配的陈旧锁不会永久阻塞启动，活动锁不会被误删。
+4. 现有 Codex App 协议行为不变，worker/source 两条路径都经过同一锁与重试逻辑；语义判断器等额外客户端若无法获取锁，应收到可诊断的忙错误，不得杀掉已有 app-server。
+5. 新增测试可稳定复现上述场景，并通过项目现有的 Node 语法检查、单元测试和回归测试。
diff --git a/.trellis/tasks/09-27-codex-start-lock-retry/task.json b/.trellis/tasks/09-27-codex-start-lock-retry/task.json
new file mode 100644
index 0000000..300e441
--- /dev/null
+++ b/.trellis/tasks/09-27-codex-start-lock-retry/task.json
@@ -0,0 +1,26 @@
+{
+  "id": "codex-start-lock-retry",
+  "name": "codex-start-lock-retry",
+  "title": "Codex 启动单实例锁与退避重试",
+  "description": "",
+  "status": "completed",
+  "dev_type": null,
+  "scope": null,
+  "package": null,
+  "priority": "P2",
+  "creator": "shiyue",
+  "assignee": "shiyue",
+  "createdAt": "2026-09-27",
+  "completedAt": "2026-09-28",
+  "branch": null,
+  "base_branch": "main",
+  "worktree_path": null,
+  "commit": null,
+  "pr_url": null,
+  "subtasks": [],
+  "children": [],
+  "parent": null,
+  "relatedFiles": [],
+  "notes": "",
+  "meta": {}
+}
diff --git a/dist-exe/cc-web-bun-linux-x64-baseline.tar.gz b/dist-exe/cc-web-bun-linux-x64-baseline.tar.gz
index 7115719..b4bab58 100644
Binary files a/dist-exe/cc-web-bun-linux-x64-baseline.tar.gz and b/dist-exe/cc-web-bun-linux-x64-baseline.tar.gz differ
diff --git a/lib/codex-app-runtime.js b/lib/codex-app-runtime.js
index eb616c2..8033de4 100644
--- a/lib/codex-app-runtime.js
+++ b/lib/codex-app-runtime.js
@@ -761,9 +761,17 @@ function createCodexAppRuntime(deps = {}) {
     if (!nextText) return '';
     if (!entry.agentMessageItems) entry.agentMessageItems = new Map();
     const currentItemText = entry.agentMessageItems.get(itemId) || '';
+    if (!entry.agentMessagePendingPrefixes) entry.agentMessagePendingPrefixes = new Map();
+    const pendingPrefix = entry.agentMessagePendingPrefixes.get(itemId) || '';
+    if (!currentItemText && !nextText.trim()) {
+      entry.agentMessagePendingPrefixes.set(itemId, `${pendingPrefix}${nextText}`);
+      return '';
+    }
+    entry.agentMessagePendingPrefixes.delete(itemId);
     const separator = agentMessageSeparator(entry, itemId, nextText);
-    const appended = separator + nextText;
-    entry.agentMessageItems.set(itemId, appendCappedText(currentItemText, nextText, RUNTIME_AGENT_ITEM_MAX_CHARS));
+    const firstText = currentItemText ? nextText : `${pendingPrefix}${nextText}`;
+    const appended = separator + firstText;
+    entry.agentMessageItems.set(itemId, appendCappedText(currentItemText, firstText, RUNTIME_AGENT_ITEM_MAX_CHARS));
     entry.fullText = appendCappedText(entry.fullText || '', appended, RUNTIME_FULL_TEXT_MAX_CHARS);
     return capStreamDelta(appended);
   }
@@ -773,6 +781,10 @@ function createCodexAppRuntime(deps = {}) {
     if (!text) return '';
     if (!entry.agentMessageItems) entry.agentMessageItems = new Map();
     const currentItemText = entry.agentMessageItems.get(item.id) || '';
+    if (!entry.agentMessagePendingPrefixes) entry.agentMessagePendingPrefixes = new Map();
+    const pendingPrefix = entry.agentMessagePendingPrefixes.get(item.id) || '';
+    entry.agentMessagePendingPrefixes.delete(item.id);
+    if (!currentItemText && !text.trim()) return '';
     if (currentItemText && text.startsWith(currentItemText)) {
       const remainder = text.slice(currentItemText.length);
       entry.agentMessageItems.set(item.id, keepTail(text, RUNTIME_AGENT_ITEM_MAX_CHARS));
@@ -780,9 +792,12 @@ function createCodexAppRuntime(deps = {}) {
       return capStreamDelta(remainder);
     }
     if (currentItemText === text) return '';
-    const separator = agentMessageSeparator(entry, item.id, text);
-    const appended = separator + text;
-    entry.agentMessageItems.set(item.id, keepTail(text, RUNTIME_AGENT_ITEM_MAX_CHARS));
+    const completedText = !currentItemText && pendingPrefix && !text.startsWith(pendingPrefix)
+      ? `${pendingPrefix}${text}`
+      : text;
+    const separator = agentMessageSeparator(entry, item.id, completedText);
+    const appended = separator + completedText;
+    entry.agentMessageItems.set(item.id, keepTail(completedText, RUNTIME_AGENT_ITEM_MAX_CHARS));
     entry.fullText = appendCappedText(entry.fullText || '', appended, RUNTIME_FULL_TEXT_MAX_CHARS);
     return capStreamDelta(appended);
   }
diff --git a/lib/codex-app-server-client.js b/lib/codex-app-server-client.js
index 1ec67ec..084e5dd 100644
--- a/lib/codex-app-server-client.js
+++ b/lib/codex-app-server-client.js
@@ -2,6 +2,39 @@
 
 const readline = require('readline');
 const { spawn } = require('child_process');
+const {
+  acquireCodexHomeLock,
+} = require('./codex-home-lock');
+
+const DEFAULT_START_RETRY_ATTEMPTS = 4;
+const DEFAULT_START_RETRY_DELAY_MS = 500;
+const DEFAULT_START_RETRY_MAX_DELAY_MS = 5000;
+
+function positiveInt(value, fallback, { min = 1, max = Number.MAX_SAFE_INTEGER } = {}) {
+  const parsed = Number.parseInt(String(value ?? ''), 10);
+  if (!Number.isFinite(parsed) || parsed < min) return fallback;
+  return Math.min(parsed, max);
+}
+
+function isCodexHomeBusyError(value) {
+  const parts = [];
+  const visit = (item, depth = 0) => {
+    if (!item || depth > 3) return;
+    if (typeof item === 'string') parts.push(item);
+    else if (typeof item === 'object') {
+      for (const key of ['message', 'stderr', 'cause', 'code', 'details']) visit(item[key], depth + 1);
+    }
+  };
+  visit(value);
+  const text = parts.join(' ');
+  return /database\s+(?:is\s+)?locked|database\s+table\s+is\s+locked|SQLITE_BUSY(?:_TIMEOUT)?|failed\s+to\s+(?:open|initialize)\s+(?:state|log|database)|failed\s+to\s+initialize\s+state\s+runtime/i.test(text);
+}
+
+function retryDelayMs(attempt, base, max) {
+  const exponential = Math.min(max, base * (2 ** Math.max(0, attempt - 1)));
+  const jitter = Math.floor(Math.random() * Math.max(1, Math.min(100, exponential * 0.2)));
+  return Math.min(max, exponential + jitter);
+}
 
 function createCodexAppServerClient(options = {}) {
   const command = options.command || 'codex';
@@ -26,6 +59,11 @@ function createCodexAppServerClient(options = {}) {
   let nextId = 1;
   let initPromise = null;
   let exited = false;
+  let processExitPromise = null;
+  let resolveProcessExit = null;
+  let lockHandle = null;
+  let lastStartError = null;
+  let stopRequested = false;
   const pending = new Map();
 
   function rejectAllPending(err) {
@@ -137,8 +175,14 @@ function createCodexAppServerClient(options = {}) {
     return request('config/mcpServer/reload', {}, 30000);
   }
 
-  function start() {
-    if (initPromise) return initPromise;
+  function releaseLock() {
+    const current = lockHandle;
+    lockHandle = null;
+    if (current) Promise.resolve(current.release()).catch(() => {});
+  }
+
+  function spawnAndInitialize(lock) {
+    lockHandle = lock;
     exited = false;
     proc = spawn(command, args, {
       env,
@@ -147,6 +191,8 @@ function createCodexAppServerClient(options = {}) {
       windowsHide: true,
     });
 
+    processExitPromise = new Promise((resolve) => { resolveProcessExit = resolve; });
+
     let stderr = '';
     proc.stderr.on('data', (chunk) => {
       stderr += chunk.toString();
@@ -164,15 +210,21 @@ function createCodexAppServerClient(options = {}) {
       err.signal = signal;
       err.stderr = stderr;
       rejectAllPending(err);
+      releaseLock();
+      if (resolveProcessExit) resolveProcessExit({ code, signal, stderr });
+      resolveProcessExit = null;
       onExit({ code, signal, stderr });
     });
 
     proc.on('error', (err) => {
       rejectAllPending(err);
+      releaseLock();
+      if (resolveProcessExit) resolveProcessExit({ code: null, signal: null, stderr: err.message });
+      resolveProcessExit = null;
       onExit({ code: null, signal: null, stderr: err.message });
     });
 
-    initPromise = request('initialize', {
+    return request('initialize', {
       clientInfo,
       capabilities: { experimentalApi: true },
     }, 30000)
@@ -182,28 +234,108 @@ function createCodexAppServerClient(options = {}) {
         return result;
       })
       .catch((err) => {
-        stop();
         throw err;
       });
+  }
+
+  async function terminateProcessAndWait() {
+    const child = proc;
+    if (!child || exited) {
+      releaseLock();
+      return;
+    }
+    try { child.kill('SIGTERM'); } catch {}
+    const timer = setTimeout(() => {
+      try { if (!child.killed) child.kill('SIGKILL'); } catch {}
+    }, 3000);
+    try {
+      await processExitPromise;
+    } finally {
+      clearTimeout(timer);
+    }
+  }
+
+  async function startWithRetry() {
+    const env = options.env || process.env;
+    const attempts = positiveInt(
+      options.startRetryAttempts ?? env.CC_WEB_CODEX_START_RETRY_ATTEMPTS,
+      DEFAULT_START_RETRY_ATTEMPTS,
+      { min: 1, max: 8 },
+    );
+    const baseDelay = positiveInt(
+      options.startRetryDelayMs ?? env.CC_WEB_CODEX_START_RETRY_DELAY_MS,
+      DEFAULT_START_RETRY_DELAY_MS,
+      { min: 0, max: 30_000 },
+    );
+    const maxDelay = positiveInt(
+      options.startRetryMaxDelayMs ?? env.CC_WEB_CODEX_START_RETRY_MAX_DELAY_MS,
+      DEFAULT_START_RETRY_MAX_DELAY_MS,
+      { min: baseDelay || 1, max: 60_000 },
+    );
+
+    for (let attempt = 1; attempt <= attempts; attempt += 1) {
+      if (stopRequested) {
+        const aborted = new Error('Codex app-server 启动已取消。');
+        aborted.code = 'CODEX_APP_START_CANCELLED';
+        throw aborted;
+      }
+      const lock = await acquireCodexHomeLock({
+        env,
+        waitMs: options.lockWaitMs,
+        lockPath: options.lockPath,
+      });
+      if (stopRequested) {
+        await lock.release();
+        const aborted = new Error('Codex app-server 启动已取消。');
+        aborted.code = 'CODEX_APP_START_CANCELLED';
+        throw aborted;
+      }
+      try {
+        const result = await spawnAndInitialize(lock);
+        lastStartError = null;
+        return result;
+      } catch (error) {
+        lastStartError = error;
+        await terminateProcessAndWait();
+        if (!isCodexHomeBusyError(error) || attempt >= attempts) {
+          const detail = error?.stderr || error?.message || String(error || '');
+          const finalError = new Error(`Codex app-server 启动失败（尝试 ${attempt}/${attempts}）：${detail}`);
+          finalError.code = error?.code || 'CODEX_APP_START_FAILED';
+          finalError.cause = error;
+          finalError.stderr = error?.stderr || '';
+          finalError.lockPath = lock.path;
+          throw finalError;
+        }
+        const delay = retryDelayMs(attempt, baseDelay, maxDelay);
+        onLog('WARN', 'codex_app_server_start_retry', {
+          attempt,
+          nextAttempt: attempt + 1,
+          delayMs: delay,
+          reason: 'sqlite_busy',
+          lockPath: lock.path,
+        });
+        await new Promise((resolve) => setTimeout(resolve, delay));
+      }
+    }
+    throw lastStartError || new Error('Codex app-server 启动失败。');
+  }
+
+  function start() {
+    if (initPromise) return initPromise;
+    stopRequested = false;
+    initPromise = startWithRetry();
 
     return initPromise;
   }
 
   function stop() {
+    stopRequested = true;
     initPromise = null;
     if (rl) {
       try { rl.close(); } catch {}
       rl = null;
     }
-    if (proc && !exited) {
-      try { proc.kill('SIGTERM'); } catch {}
-      setTimeout(() => {
-        try {
-          if (proc && !proc.killed) proc.kill('SIGKILL');
-        } catch {}
-      }, 3000);
-    }
-    proc = null;
+    terminateProcessAndWait().catch(() => {});
     rejectAllPending(new Error('Codex app-server 已停止。'));
   }
 
diff --git a/lib/codex-home-lock.js b/lib/codex-home-lock.js
new file mode 100644
index 0000000..3962bc4
--- /dev/null
+++ b/lib/codex-home-lock.js
@@ -0,0 +1,189 @@
+'use strict';
+
+const crypto = require('crypto');
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+
+const DEFAULT_LOCK_WAIT_MS = 30_000;
+const DEFAULT_LOCK_POLL_MS = 200;
+const DEFAULT_LOCK_POLL_MAX_MS = 2_000;
+const INVALID_LOCK_GRACE_MS = 2_000;
+
+
+function positiveInt(value, fallback, { min = 1, max = Number.MAX_SAFE_INTEGER } = {}) {
+  const parsed = Number.parseInt(String(value ?? ''), 10);
+  if (!Number.isFinite(parsed) || parsed < min) return fallback;
+  return Math.min(parsed, max);
+}
+
+function resolveCodexHome(env = process.env) {
+  const explicit = String(env?.CODEX_HOME || '').trim();
+  if (explicit) return path.resolve(explicit);
+  const home = String(env?.HOME || env?.USERPROFILE || os.homedir() || '').trim();
+  return home ? path.join(home, '.codex') : '';
+}
+
+function readProcessStartTime(pid) {
+  if (!Number.isInteger(pid) || pid <= 0 || process.platform === 'win32') return null;
+  try {
+    const stat = fs.readFileSync(`/proc/${pid}/stat`, 'utf8');
+    const closingParen = stat.lastIndexOf(')');
+    if (closingParen < 0) return null;
+    const fields = stat.slice(closingParen + 1).trim().split(/\s+/);
+    // The remainder starts at stat field 3; field 22 is index 19 here.
+    return fields[19] || null;
+  } catch {
+    return null;
+  }
+}
+
+function currentProcessOwner() {
+  return {
+    pid: process.pid,
+    startTime: readProcessStartTime(process.pid),
+    token: crypto.randomBytes(16).toString('hex'),
+    createdAt: new Date().toISOString(),
+  };
+}
+
+function readLock(lockPath) {
+  try {
+    const stat = fs.statSync(lockPath);
+    let owner = null;
+    try {
+      const parsed = JSON.parse(fs.readFileSync(lockPath, 'utf8'));
+      if (parsed && typeof parsed === 'object') owner = parsed;
+    } catch {}
+    return { owner, mtimeMs: stat.mtimeMs };
+  } catch (error) {
+    if (error?.code === 'ENOENT') return null;
+    return { owner: null, mtimeMs: 0 };
+  }
+}
+
+function processAlive(pid) {
+  if (!Number.isInteger(pid) || pid <= 0) return false;
+  try {
+    process.kill(pid, 0);
+    return true;
+  } catch (error) {
+    return error?.code === 'EPERM';
+  }
+}
+
+function lockOwnerActive(owner) {
+  if (!owner || !Number.isInteger(Number(owner.pid))) return false;
+  const pid = Number(owner.pid);
+  if (!processAlive(pid)) return false;
+  const recordedStart = owner.startTime == null ? null : String(owner.startTime);
+  const currentStart = readProcessStartTime(pid);
+  if (recordedStart && currentStart && recordedStart !== currentStart) return false;
+  // On platforms without /proc, a live PID is the strongest available signal.
+  return true;
+}
+
+function lockOwnerSummary(owner) {
+  if (!owner || typeof owner !== 'object') return null;
+  return {
+    pid: Number.isInteger(Number(owner.pid)) ? Number(owner.pid) : null,
+    startTime: owner.startTime || null,
+    createdAt: owner.createdAt || null,
+  };
+}
+
+function wait(ms) {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+async function acquireCodexHomeLock(options = {}) {
+  const lockPath = options.lockPath
+    ? path.resolve(String(options.lockPath))
+    : (() => {
+      const home = resolveCodexHome(options.env || process.env);
+      return home ? path.join(home, '.cc-web-codex.lock') : '';
+    })();
+  if (!lockPath) {
+    return { path: '', owner: null, release: async () => {} };
+  }
+
+  const waitMs = positiveInt(
+    options.waitMs ?? options.env?.CC_WEB_CODEX_LOCK_WAIT_MS,
+    DEFAULT_LOCK_WAIT_MS,
+    { min: 0, max: 10 * 60 * 1000 },
+  );
+  const pollMs = positiveInt(options.pollMs, DEFAULT_LOCK_POLL_MS, { min: 10, max: 5000 });
+  const pollMaxMs = positiveInt(options.pollMaxMs, DEFAULT_LOCK_POLL_MAX_MS, { min: pollMs, max: 10_000 });
+  const owner = currentProcessOwner();
+  const startedAt = Date.now();
+  let lastOwner = null;
+
+  fs.mkdirSync(path.dirname(lockPath), { recursive: true });
+  while (true) {
+    try {
+      const fd = fs.openSync(lockPath, 'wx', 0o600);
+      try {
+        fs.writeFileSync(fd, `${JSON.stringify(owner)}\n`, 'utf8');
+      } finally {
+        fs.closeSync(fd);
+      }
+      return createLockHandle(lockPath, owner);
+    } catch (error) {
+      if (error?.code !== 'EEXIST') throw error;
+      const existing = readLock(lockPath);
+      lastOwner = existing?.owner || null;
+      const ageMs = existing ? Math.max(0, Date.now() - Number(existing.mtimeMs || 0)) : 0;
+      const stale = existing && (
+        (existing.owner && !lockOwnerActive(existing.owner))
+        || (!existing.owner && ageMs >= INVALID_LOCK_GRACE_MS)
+      );
+      if (stale) {
+        try {
+          const latest = readLock(lockPath);
+          if (latest?.owner?.token === existing.owner?.token || (!latest?.owner && ageMs >= INVALID_LOCK_GRACE_MS)) {
+            fs.unlinkSync(lockPath);
+            continue;
+          }
+        } catch (unlinkError) {
+          if (unlinkError?.code === 'ENOENT') continue;
+        }
+      }
+
+      if (Date.now() - startedAt >= waitMs) {
+        const err = new Error(`Codex CODEX_HOME 已被占用: ${lockPath}`);
+        err.code = 'CODEX_HOME_LOCK_BUSY';
+        err.lockPath = lockPath;
+        err.owner = lockOwnerSummary(lastOwner);
+        throw err;
+      }
+      const elapsed = Date.now() - startedAt;
+      const base = Math.min(pollMaxMs, pollMs * (2 ** Math.min(4, Math.floor(elapsed / 1000))));
+      const jitter = Math.floor(Math.random() * Math.max(1, Math.min(100, base * 0.2)));
+      await wait(Math.min(pollMaxMs, base + jitter));
+    }
+  }
+}
+
+function createLockHandle(lockPath, owner) {
+  let released = false;
+  return {
+    path: lockPath,
+    owner,
+    release: async () => {
+      if (released) return;
+      released = true;
+      try {
+        const onDisk = readLock(lockPath)?.owner;
+        if (onDisk?.token === owner.token) fs.unlinkSync(lockPath);
+      } catch {}
+    },
+  };
+}
+
+module.exports = {
+  DEFAULT_LOCK_WAIT_MS,
+  acquireCodexHomeLock,
+  lockOwnerActive,
+  readProcessStartTime,
+  resolveCodexHome,
+};
diff --git a/package.json b/package.json
index 288dffa..81e6c3c 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,8 @@
   "scripts": {
     "start": "node server.js",
     "build:single-exe": "node scripts/build-single-exe.js",
-    "regression": "node scripts/regression.js"
+    "regression": "node scripts/regression.js",
+    "test:codex-start-lock": "node scripts/codex-start-lock-unit.js"
   },
   "dependencies": {
     "echarts": "5.6.0",
diff --git a/public/app.js b/public/app.js
index da09387..abf56a4 100644
--- a/public/app.js
+++ b/public/app.js
@@ -9023,7 +9023,12 @@
 
   function renderMarkdown(text) {
     if (!text) return '<div class="typing-indicator"><span></span><span></span><span></span></div>';
-    try { return marked.parse(text); }
+    try {
+      const normalizedText = typeof window.ccNormalizeMarkdownText === 'function'
+        ? window.ccNormalizeMarkdownText(text)
+        : text;
+      return marked.parse(normalizedText);
+    }
     catch { return escapeHtml(text); }
   }
 
diff --git a/public/index.html b/public/index.html
index 34f9c72..463d52b 100644
--- a/public/index.html
+++ b/public/index.html
@@ -425,6 +425,7 @@
   <script>window.ccWebFrontendAssetVersion = '__CC_WEB_FRONTEND_ASSET_VERSION__';</script>
   <script src="task-board.js?v=__CC_WEB_FRONTEND_ASSET_VERSION__"></script>
   <script src="gitea-workflow.js?v=__CC_WEB_GITEA_WORKFLOW_ASSET_VERSION__"></script>
+  <script src="markdown-normalizer.js?v=__CC_WEB_FRONTEND_ASSET_VERSION__"></script>
   <script src="app.js?v=__CC_WEB_FRONTEND_ASSET_VERSION__"></script>
 </body>
 </html>
diff --git a/public/markdown-normalizer.js b/public/markdown-normalizer.js
new file mode 100644
index 0000000..774c378
--- /dev/null
+++ b/public/markdown-normalizer.js
@@ -0,0 +1,88 @@
+(function (root, factory) {
+  const normalize = factory();
+  if (typeof module === 'object' && module.exports) module.exports = normalize;
+  if (root) root.ccNormalizeMarkdownText = normalize;
+})(typeof globalThis !== 'undefined' ? globalThis : this, function () {
+  const CODE_LIKE_PATTERN = /(?:=>|[{};]|^\s*(?:const|let|var|function|class|return|import|export|def|print|console\.)\b|<\/?[a-z][^>]*>)/im;
+  const FENCE_PATTERN = /^ {0,3}(`{3,}|~{3,})/;
+
+  function indentationWidth(line) {
+    let width = 0;
+    for (const character of line.match(/^[ \t]*/)?.[0] || '') {
+      width = character === '\t' ? width + (4 - (width % 4)) : width + 1;
+    }
+    return width;
+  }
+
+  function removeIndent(line, width) {
+    let column = 0;
+    let index = 0;
+    while (index < line.length && column < width) {
+      const character = line[index];
+      if (character !== ' ' && character !== '\t') break;
+      const nextColumn = character === '\t' ? column + (4 - (column % 4)) : column + 1;
+      index += 1;
+      if (nextColumn > width) return `${' '.repeat(nextColumn - width)}${line.slice(index)}`;
+      column = nextColumn;
+    }
+    return line.slice(index);
+  }
+
+  function isNaturalLanguage(lines) {
+    const text = lines.map((line) => line.trim()).join(' ').trim();
+    if (!text || CODE_LIKE_PATTERN.test(text)) return false;
+
+    const cjkCount = (text.match(/[\u3400-\u9fff]/g) || []).length;
+    if (cjkCount >= 4) return /[。！？；：]/.test(text);
+
+    const wordCount = (text.match(/[a-z][a-z'-]*/gi) || []).length;
+    return wordCount >= 8 && /[.!?]/.test(text);
+  }
+
+  function normalizeParagraph(lines) {
+    const contentLines = lines.filter((line) => line.trim());
+    if (contentLines.length === 0) return lines;
+
+    const commonIndent = Math.min(...contentLines.map(indentationWidth));
+    if (commonIndent < 4 || !isNaturalLanguage(contentLines)) return lines;
+
+    return lines.map((line) => (line.trim() ? removeIndent(line, commonIndent) : line));
+  }
+
+  return function normalizeMarkdownText(value) {
+    const lines = String(value ?? '').split('\n');
+    const output = [];
+    let paragraph = [];
+    let fence = null;
+
+    function flushParagraph() {
+      if (paragraph.length > 0) output.push(...normalizeParagraph(paragraph));
+      paragraph = [];
+    }
+
+    for (const line of lines) {
+      const fenceMatch = line.match(FENCE_PATTERN);
+      if (fence) {
+        output.push(line);
+        if (fenceMatch && fenceMatch[1][0] === fence.character && fenceMatch[1].length >= fence.length) {
+          fence = null;
+        }
+        continue;
+      }
+
+      if (fenceMatch) {
+        flushParagraph();
+        fence = { character: fenceMatch[1][0], length: fenceMatch[1].length };
+        output.push(line);
+      } else if (!line.trim() || /^\s{0,3}<\/?[a-z][^>]*>/i.test(line)) {
+        flushParagraph();
+        output.push(line);
+      } else {
+        paragraph.push(line);
+      }
+    }
+
+    flushParagraph();
+    return output.join('\n');
+  };
+});
diff --git a/scripts/codex-start-lock-unit.js b/scripts/codex-start-lock-unit.js
new file mode 100644
index 0000000..ab0026c
--- /dev/null
+++ b/scripts/codex-start-lock-unit.js
@@ -0,0 +1,126 @@
+#!/usr/bin/env node
+
+'use strict';
+
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const os = require('node:os');
+const path = require('node:path');
+const { createCodexAppServerClient } = require('../lib/codex-app-server-client');
+const {
+  acquireCodexHomeLock,
+  readProcessStartTime,
+} = require('../lib/codex-home-lock');
+
+const FAKE_SERVER = path.join(os.tmpdir(), `ccweb-fake-codex-${process.pid}.js`);
+fs.writeFileSync(FAKE_SERVER, String.raw`
+'use strict';
+const fs = require('fs');
+const readline = require('readline');
+const attemptFile = process.env.FAKE_ATTEMPT_FILE;
+const failureMode = process.env.FAKE_FAILURE_MODE || 'busy';
+let attempt = 0;
+try { attempt = Number(fs.readFileSync(attemptFile, 'utf8')) || 0; } catch {}
+attempt += 1;
+fs.writeFileSync(attemptFile, String(attempt));
+if (attempt <= Number(process.env.FAKE_BUSY_ATTEMPTS || 0)) {
+  process.stderr.write(failureMode === 'busy' ? 'database is locked (code: 5)\n' : 'fatal config error\n');
+  process.exit(1);
+}
+const rl = readline.createInterface({ input: process.stdin });
+rl.on('line', (line) => {
+  let message;
+  try { message = JSON.parse(line); } catch { return; }
+  if (message.id && message.method === 'initialize') {
+    process.stdout.write(JSON.stringify({ id: message.id, result: { serverInfo: { name: 'fake' } } }) + '\n');
+  }
+});
+`, 'utf8');
+
+function tempHome() {
+  return fs.mkdtempSync(path.join(os.tmpdir(), 'ccweb-codex-home-'));
+}
+
+async function testLockMutualExclusion() {
+  const home = tempHome();
+  const first = await acquireCodexHomeLock({ env: { CODEX_HOME: home } });
+  await assert.rejects(
+    () => acquireCodexHomeLock({ env: { CODEX_HOME: home }, waitMs: 80, pollMs: 10, pollMaxMs: 20 }),
+    (error) => error.code === 'CODEX_HOME_LOCK_BUSY' && error.owner?.pid === process.pid,
+  );
+  await first.release();
+  assert.equal(fs.existsSync(path.join(home, '.cc-web-codex.lock')), false);
+}
+
+async function testStaleLockAndPidReuseProtection() {
+  const home = tempHome();
+  const lockPath = path.join(home, '.cc-web-codex.lock');
+  fs.writeFileSync(lockPath, JSON.stringify({
+    pid: process.pid,
+    startTime: 'definitely-not-the-current-start-time',
+    token: 'stale',
+    createdAt: new Date().toISOString(),
+  }));
+  const lock = await acquireCodexHomeLock({ env: { CODEX_HOME: home }, waitMs: 100 });
+  assert.equal(lock.owner.pid, process.pid);
+  await lock.release();
+  assert.equal(fs.existsSync(lockPath), false);
+  assert.equal(typeof readProcessStartTime(process.pid), 'string');
+}
+
+async function createClient(home, attemptFile, extraEnv = {}) {
+  return createCodexAppServerClient({
+    command: process.execPath,
+    args: [FAKE_SERVER],
+    env: {
+      ...process.env,
+      CODEX_HOME: home,
+      FAKE_ATTEMPT_FILE: attemptFile,
+      ...extraEnv,
+    },
+    startRetryDelayMs: 1,
+    startRetryMaxDelayMs: 2,
+    lockWaitMs: 100,
+  });
+}
+
+async function testBusyRetryAndRelease() {
+  const home = tempHome();
+  const attempts = path.join(home, 'attempts');
+  fs.writeFileSync(attempts, '0');
+  const client = await createClient(home, attempts, { FAKE_BUSY_ATTEMPTS: '2' });
+  await client.start();
+  assert.equal(fs.readFileSync(attempts, 'utf8'), '3');
+  client.stop();
+  for (let i = 0; i < 30 && fs.existsSync(path.join(home, '.cc-web-codex.lock')); i += 1) {
+    await new Promise((resolve) => setTimeout(resolve, 10));
+  }
+  assert.equal(fs.existsSync(path.join(home, '.cc-web-codex.lock')), false);
+}
+
+async function testNonBusyDoesNotRetry() {
+  const home = tempHome();
+  const attempts = path.join(home, 'attempts');
+  fs.writeFileSync(attempts, '0');
+  const client = await createClient(home, attempts, { FAKE_BUSY_ATTEMPTS: '1', FAKE_FAILURE_MODE: 'fatal' });
+  await assert.rejects(() => client.start(), (error) => error.code === 'CODEX_APP_START_FAILED');
+  assert.equal(fs.readFileSync(attempts, 'utf8'), '1');
+  assert.equal(fs.existsSync(path.join(home, '.cc-web-codex.lock')), false);
+}
+
+async function main() {
+  try {
+    await testLockMutualExclusion();
+    await testStaleLockAndPidReuseProtection();
+    await testBusyRetryAndRelease();
+    await testNonBusyDoesNotRetry();
+    console.log('codex-start-lock-unit: ok');
+  } finally {
+    try { fs.unlinkSync(FAKE_SERVER); } catch {}
+  }
+}
+
+main().catch((error) => {
+  console.error(error.stack || error);
+  process.exitCode = 1;
+});
diff --git a/scripts/regression.js b/scripts/regression.js
index b4b39ad..632a5b0 100644
--- a/scripts/regression.js
+++ b/scripts/regression.js
@@ -1613,6 +1613,91 @@ function assertFrontendMarkdownLinkContract() {
   assert(styleSource.includes('.msg-bubble a.local-file-link'), 'Local file links should have a distinct message style');
 }
 
+function assertMarkdownRenderingContract() {
+  const source = fs.readFileSync(PUBLIC_APP_PATH, 'utf8');
+  const indexSource = fs.readFileSync(PUBLIC_INDEX_PATH, 'utf8');
+  const normalizeMarkdownText = require(path.join(PUBLIC_DIR, 'markdown-normalizer.js'));
+  const { createCodexAppRuntime } = require(path.join(REPO_DIR, 'lib', 'codex-app-runtime'));
+  const assistantRendererStart = source.indexOf('function renderAssistantContent');
+  const assistantRendererEnd = source.indexOf('function createAssistantImageElement', assistantRendererStart);
+  const assistantRenderer = assistantRendererStart >= 0 && assistantRendererEnd > assistantRendererStart
+    ? source.slice(assistantRendererStart, assistantRendererEnd)
+    : '';
+
+  const indentedChineseText = '        目前代码里 `PlanList` 的运行时和前端渲染逻辑仍然存在，问题更像是事件没有被识别。';
+  assert(
+    normalizeMarkdownText(indentedChineseText).startsWith('目前代码里'),
+    'Clearly indented Chinese prose should be normalized before Markdown parsing'
+  );
+  assert(
+    normalizeMarkdownText('    这是一段普通说明。\n\n    这是下一段普通说明。') === '这是一段普通说明。\n\n这是下一段普通说明。',
+    'Multi-paragraph prose indentation should be removed independently'
+  );
+  assert(normalizeMarkdownText('\t这是一段普通说明。') === '这是一段普通说明。', 'Tab-indented prose should also be normalized');
+  const fencedCode = '说明文字。\n\n```js\n    const value = 1;\n```';
+  assert(normalizeMarkdownText(fencedCode) === fencedCode, 'Explicit fenced code blocks should remain byte-for-byte unchanged');
+  const indentedCode = '    const value = 1;\n    console.log(value);';
+  assert(normalizeMarkdownText(indentedCode) === indentedCode, 'Indented source code should retain its indentation');
+  const whitespaceOnly = '结论一。\n   \n结论二。';
+  assert(normalizeMarkdownText(whitespaceOnly) === whitespaceOnly, 'Whitespace-only lines should never be treated as prose indentation');
+  assert(
+    assistantRenderer.includes("block.type === 'todo_list'") && assistantRenderer.includes('createTodoListElement(block)'),
+    'Structured todo_list blocks should continue to render through the PlanList card path'
+  );
+  assert(
+    indexSource.includes('markdown-normalizer.js')
+      && source.includes('typeof window.ccNormalizeMarkdownText === \'function\'')
+      && source.includes('return marked.parse(normalizedText)'),
+    'Assistant Markdown rendering should load and apply the shared text normalizer'
+  );
+
+  const streamed = [];
+  const runtime = createCodexAppRuntime({
+    wsSend: (_ws, payload) => streamed.push(payload),
+    loadSession: () => null,
+    saveSession: () => {},
+  });
+  const entry = { ws: {}, toolCalls: [], fullText: '' };
+  runtime.processCodexAppNotification(entry, {
+    method: 'item/agentMessage/delta',
+    params: { itemId: 'msg-first', delta: '先给出的结论。' },
+  }, 'markdown-session');
+  runtime.processCodexAppNotification(entry, {
+    method: 'item/completed',
+    params: { item: { id: 'msg-first', type: 'agentMessage', text: '先给出的结论。' } },
+  }, 'markdown-session');
+  ['rs-noise-1', 'rs-noise-2', 'rs-noise-3'].forEach((itemId) => {
+    runtime.processCodexAppNotification(entry, {
+      method: 'item/agentMessage/delta',
+      params: { itemId, delta: ' ' },
+    }, 'markdown-session');
+    runtime.processCodexAppNotification(entry, {
+      method: 'item/completed',
+      params: { item: { id: itemId, type: 'agentMessage', text: ' ' } },
+    }, 'markdown-session');
+  });
+  runtime.processCodexAppNotification(entry, {
+    method: 'item/agentMessage/delta',
+    params: { itemId: 'msg-second', delta: '普通正文不应带缩进。' },
+  }, 'markdown-session');
+  const lastLine = entry.fullText.split('\n').filter((line) => line.trim()).pop() || '';
+  assert(lastLine === '普通正文不应带缩进。', 'Whitespace-only agent message chunks must not indent the following message text');
+  assert(entry.fullText.startsWith('先给出的结论。'), 'Whitespace-only chunks must not create leading whitespace on the first message');
+  assert(
+    !streamed.some((payload) => payload.type === 'text_delta' && !payload.text.trim()),
+    'Whitespace-only chunks must not be streamed to the transcript'
+  );
+  runtime.processCodexAppNotification(entry, {
+    method: 'item/agentMessage/delta',
+    params: { itemId: 'msg-code', delta: '    ' },
+  }, 'markdown-session');
+  runtime.processCodexAppNotification(entry, {
+    method: 'item/agentMessage/delta',
+    params: { itemId: 'msg-code', delta: 'const value = 1;' },
+  }, 'markdown-session');
+  assert(entry.fullText.includes('    const value = 1;'), 'Leading indentation should be retained when later chunks complete the same code message');
+}
+
 function assertFrontendMcpReloadContract() {
   const source = fs.readFileSync(PUBLIC_APP_PATH, 'utf8');
   assert(source.includes('function mcpStartupStatusToastText(status)'), 'Frontend should format MCP startup status toast text');
@@ -7162,6 +7247,12 @@ async function main() {
       console.log('Plan List progress regression checks passed.');
       return;
     }
+    if (regressionTarget === 'markdown-rendering') {
+      assertMarkdownRenderingContract();
+      assertPlanListProgressContract();
+      console.log('Markdown rendering regression checks passed.');
+      return;
+    }
     if (regressionTarget === 'runtime-image-send') {
       await runRuntimeImageSendTarget();
       console.log('Runtime image send regression checks passed.');
@@ -7300,6 +7391,7 @@ async function main() {
   assertComposerSlashRoutingContract();
   assertFrontendCcwebPromptContract();
   assertFrontendMarkdownLinkContract();
+  assertMarkdownRenderingContract();
   assertMockCodexAppPromptUserNotTextTriggered();
   assertFrontendMcpReloadContract();
   assertCcwebMcpRecoveryContract();
diff --git a/server.js b/server.js
index 7682a6d..230471c 100644
--- a/server.js
+++ b/server.js
@@ -8677,6 +8677,9 @@ async function judgeJavascriptSemanticBranch(lastMessage, candidates, cwd) {
         args: spec.args,
         env: spec.env,
         cwd: cwd || process.cwd(),
+        // 语义判断器是一次性辅助客户端；主 Codex App 已占用同一 CODEX_HOME
+        // 时快速失败，避免把一个不影响主会话的判断请求排队 30 秒。
+        lockWaitMs: 1000,
         clientInfo: { name: 'ccweb_semantic_judge', title: 'CC-Web Semantic Judge', version: '1.0.0' },
         postInitialize: codexAppPostInitialize,
         onNotification(notification) {