diff --git a/README.md b/README.md
index 2099fb0..0b17840 100644
--- a/README.md
+++ b/README.md
@@ -550,6 +550,7 @@ Cloudflare 模式下，插件不会再调用 Cloudflare API 创建路由。
 - 使用自定义密码或自动生成密码
 - 在密码页填写密码并提交注册表单
 - 后台会在真正把 Step 3 记为完成前，再确认页面是否已经推进；如果此时出现认证页 `重试` 页面，或 `/email-verification` 上的 `405 / Route Error` 重试页，会先通过共享恢复逻辑最多自动点击 5 次 `重试` 尝试恢复，再继续后续链路
+- Step 3 收尾阶段如果页面切换导致旧内容脚本失联，后台单次消息等待不会再卡住超过当前收尾预算；若最终仍未恢复，则会输出中文的步骤级错误，而不是直接暴露底层英文通信超时
 
 实际使用的密码会写入会话状态，并同步到侧边栏显示。
 
diff --git a/background.js b/background.js
index bbc85c7..a2e2e93 100644
--- a/background.js
+++ b/background.js
@@ -6256,6 +6256,7 @@ const signupFlowHelpers = self.MultiPageSignupFlowHelpers?.createSignupFlowHelpe
   isGeneratedAliasProvider,
   isReusableGeneratedAliasEmail,
   isSignupEmailVerificationPageUrl,
+  isRetryableContentScriptTransportError,
   isHotmailProvider,
   isLuckmailProvider,
   isSignupPasswordPageUrl,
diff --git a/background/signup-flow-helpers.js b/background/signup-flow-helpers.js
index 3ba844b..dc64c9b 100644
--- a/background/signup-flow-helpers.js
+++ b/background/signup-flow-helpers.js
@@ -3,6 +3,7 @@
 })(typeof self !== 'undefined' ? self : globalThis, function createSignupFlowHelpersModule() {
   function createSignupFlowHelpers(deps = {}) {
     const {
+      addLog,
       buildGeneratedAliasEmail,
       chrome,
       ensureContentScriptReadyOnTab,
@@ -12,6 +13,7 @@
       isGeneratedAliasProvider,
       isReusableGeneratedAliasEmail,
       isHotmailProvider,
+      isRetryableContentScriptTransportError = () => false,
       isLuckmailProvider,
       isSignupEmailVerificationPageUrl,
       isSignupPasswordPageUrl,
@@ -164,20 +166,32 @@
         logMessage: `步骤 ${step}：认证页仍在切换，正在等待页面恢复后继续确认提交流程...`,
       });
 
-      const result = await sendToContentScriptResilient('signup-page', {
-        type: 'PREPARE_SIGNUP_VERIFICATION',
-        step,
-        source: 'background',
-        payload: {
-          password: password || '',
-          prepareSource: 'step3_finalize',
-          prepareLogLabel: '步骤 3 收尾',
-        },
-      }, {
-        timeoutMs: 30000,
-        retryDelayMs: 700,
-        logMessage: `步骤 ${step}：密码已提交，正在确认是否进入下一页面，必要时自动恢复重试页...`,
-      });
+      let result;
+      try {
+        result = await sendToContentScriptResilient('signup-page', {
+          type: 'PREPARE_SIGNUP_VERIFICATION',
+          step,
+          source: 'background',
+          payload: {
+            password: password || '',
+            prepareSource: 'step3_finalize',
+            prepareLogLabel: '步骤 3 收尾',
+          },
+        }, {
+          timeoutMs: 30000,
+          retryDelayMs: 700,
+          logMessage: `步骤 ${step}：密码已提交，正在确认是否进入下一页面，必要时自动恢复重试页...`,
+        });
+      } catch (error) {
+        if (isRetryableContentScriptTransportError(error)) {
+          const message = `步骤 ${step}：认证页在提交后切换过程中页面通信超时，未能重新就绪，暂时无法确认是否进入下一页面。请重试当前轮。`;
+          if (typeof addLog === 'function') {
+            await addLog(message, 'warn');
+          }
+          throw new Error(message);
+        }
+        throw error;
+      }
 
       if (result?.error) {
         throw new Error(result.error);
diff --git a/background/tab-runtime.js b/background/tab-runtime.js
index 54f6dfc..51619cb 100644
--- a/background/tab-runtime.js
+++ b/background/tab-runtime.js
@@ -376,6 +376,17 @@
       return 30000;
     }
 
+    function resolveResponseTimeoutMs(message, requestedResponseTimeoutMs, remainingTimeoutMs = null) {
+      const fallbackTimeoutMs = getContentScriptResponseTimeoutMs(message);
+      const requestedTimeoutMs = Number.isFinite(Number(requestedResponseTimeoutMs))
+        ? Math.max(1, Math.floor(Number(requestedResponseTimeoutMs)))
+        : fallbackTimeoutMs;
+      if (!Number.isFinite(Number(remainingTimeoutMs))) {
+        return requestedTimeoutMs;
+      }
+      return Math.max(1, Math.min(requestedTimeoutMs, Math.floor(Number(remainingTimeoutMs))));
+    }
+
     function getMessageDebugLabel(source, message, tabId = null) {
       const parts = [source || 'unknown', message?.type || 'UNKNOWN'];
       if (Number.isInteger(message?.step)) parts.push(`step=${message.step}`);
@@ -439,7 +450,13 @@
           pendingCommands.delete(source);
           reject(new Error(`Content script on ${source} did not respond in ${timeout / 1000}s. Try refreshing the tab and retry.`));
         }, timeout);
-        pendingCommands.set(source, { message, resolve, reject, timer });
+        pendingCommands.set(source, {
+          message,
+          resolve,
+          reject,
+          timer,
+          responseTimeoutMs: timeout,
+        });
         console.log(LOG_PREFIX, `Command queued for ${source} (waiting for ready)`);
       });
     }
@@ -449,7 +466,7 @@
       if (pending) {
         clearTimeout(pending.timer);
         pendingCommands.delete(source);
-        sendTabMessageWithTimeout(tabId, source, pending.message).then(pending.resolve).catch(pending.reject);
+        sendTabMessageWithTimeout(tabId, source, pending.message, pending.responseTimeoutMs).then(pending.resolve).catch(pending.reject);
         console.log(LOG_PREFIX, `Flushed queued command to ${source} (tab ${tabId})`);
       }
     }
@@ -564,13 +581,13 @@
 
       if (!entry || !entry.ready) {
         throwIfStopped();
-        return queueCommand(source, message);
+        return queueCommand(source, message, responseTimeoutMs);
       }
 
       const alive = await isTabAlive(source);
       throwIfStopped();
       if (!alive) {
-        return queueCommand(source, message);
+        return queueCommand(source, message, responseTimeoutMs);
       }
 
       throwIfStopped();
@@ -592,12 +609,18 @@
       while (Date.now() - start < timeoutMs) {
         throwIfStopped();
         attempt += 1;
+        const remainingTimeoutMs = Math.max(1, timeoutMs - (Date.now() - start));
+        const effectiveResponseTimeoutMs = resolveResponseTimeoutMs(
+          message,
+          responseTimeoutMs,
+          remainingTimeoutMs
+        );
 
         try {
           return await sendToContentScript(
             source,
             message,
-            responseTimeoutMs !== undefined ? { responseTimeoutMs } : {}
+            { responseTimeoutMs: effectiveResponseTimeoutMs }
           );
         } catch (err) {
           const retryable = isRetryableContentScriptTransportError(err);
@@ -631,12 +654,18 @@
 
       while (Date.now() - start < timeoutMs) {
         throwIfStopped();
+        const remainingTimeoutMs = Math.max(1, timeoutMs - (Date.now() - start));
+        const effectiveResponseTimeoutMs = resolveResponseTimeoutMs(
+          message,
+          responseTimeoutMs,
+          remainingTimeoutMs
+        );
 
         try {
           return await sendToContentScript(
             mail.source,
             message,
-            responseTimeoutMs !== undefined ? { responseTimeoutMs } : {}
+            { responseTimeoutMs: effectiveResponseTimeoutMs }
           );
         } catch (err) {
           if (!isRetryableContentScriptTransportError(err)) {
@@ -684,6 +713,7 @@
       queueCommand,
       registerTab,
       rememberSourceLastUrl,
+      resolveResponseTimeoutMs,
       reuseOrCreateTab,
       sendTabMessageWithTimeout,
       sendToContentScript,
diff --git a/tests/background-signup-step2-branching.test.js b/tests/background-signup-step2-branching.test.js
index 1d86de6..ceba171 100644
--- a/tests/background-signup-step2-branching.test.js
+++ b/tests/background-signup-step2-branching.test.js
@@ -175,8 +175,12 @@ test('signup flow helper reuses existing managed alias email when it is still co
 test('signup flow helper finalizes step 3 submit by reusing signup verification preparation', async () => {
   let ensureCalls = 0;
   const messages = [];
+  const logs = [];
 
   const helpers = signupFlowApi.createSignupFlowHelpers({
+    addLog: async (message, level = 'info') => {
+      logs.push({ message, level });
+    },
     buildGeneratedAliasEmail: () => '',
     chrome: { tabs: { get: async () => ({ id: 31, url: 'https://auth.openai.com/create-account/password' }) } },
     ensureContentScriptReadyOnTab: async (...args) => {
@@ -188,6 +192,7 @@ test('signup flow helper finalizes step 3 submit by reusing signup verification
     isGeneratedAliasProvider: () => false,
     isReusableGeneratedAliasEmail: () => false,
     isHotmailProvider: () => false,
+    isRetryableContentScriptTransportError: () => false,
     isLuckmailProvider: () => false,
     isSignupEmailVerificationPageUrl: () => false,
     isSignupPasswordPageUrl: () => true,
@@ -206,6 +211,7 @@ test('signup flow helper finalizes step 3 submit by reusing signup verification
 
   assert.deepStrictEqual(result, { ready: true, retried: 1 });
   assert.equal(ensureCalls, 1);
+  assert.deepStrictEqual(logs, []);
   assert.deepStrictEqual(messages.find((item) => item.type === 'send')?.message, {
     type: 'PREPARE_SIGNUP_VERIFICATION',
     step: 3,
@@ -217,3 +223,45 @@ test('signup flow helper finalizes step 3 submit by reusing signup verification
     },
   });
 });
+
+test('signup flow helper rewrites retryable step 3 finalize transport timeout into a Chinese error', async () => {
+  const logs = [];
+
+  const helpers = signupFlowApi.createSignupFlowHelpers({
+    addLog: async (message, level = 'info') => {
+      logs.push({ message, level });
+    },
+    buildGeneratedAliasEmail: () => '',
+    chrome: { tabs: { get: async () => ({ id: 31, url: 'https://auth.openai.com/create-account/password' }) } },
+    ensureContentScriptReadyOnTab: async () => {},
+    ensureHotmailAccountForFlow: async () => ({}),
+    ensureLuckmailPurchaseForFlow: async () => ({}),
+    isGeneratedAliasProvider: () => false,
+    isReusableGeneratedAliasEmail: () => false,
+    isHotmailProvider: () => false,
+    isRetryableContentScriptTransportError: (error) => /did not respond in 45s/i.test(error?.message || String(error || '')),
+    isLuckmailProvider: () => false,
+    isSignupEmailVerificationPageUrl: () => false,
+    isSignupPasswordPageUrl: () => true,
+    reuseOrCreateTab: async () => 31,
+    sendToContentScriptResilient: async () => {
+      throw new Error('Content script on signup-page did not respond in 45s. Try refreshing the tab and retry.');
+    },
+    setEmailState: async () => {},
+    SIGNUP_ENTRY_URL: 'https://chatgpt.com/',
+    SIGNUP_PAGE_INJECT_FILES: ['content/utils.js', 'content/signup-page.js'],
+    waitForTabUrlMatch: async () => null,
+  });
+
+  await assert.rejects(
+    () => helpers.finalizeSignupPasswordSubmitInTab(31, 'Secret123!', 3),
+    /步骤 3：认证页在提交后切换过程中页面通信超时，未能重新就绪，暂时无法确认是否进入下一页面。请重试当前轮。/
+  );
+
+  assert.deepStrictEqual(logs, [
+    {
+      message: '步骤 3：认证页在提交后切换过程中页面通信超时，未能重新就绪，暂时无法确认是否进入下一页面。请重试当前轮。',
+      level: 'warn',
+    },
+  ]);
+});
diff --git a/tests/background-tab-runtime-module.test.js b/tests/background-tab-runtime-module.test.js
index 2398c5d..9a239cf 100644
--- a/tests/background-tab-runtime-module.test.js
+++ b/tests/background-tab-runtime-module.test.js
@@ -16,6 +16,41 @@ test('tab runtime module exposes a factory', () => {
   assert.equal(typeof api?.createTabRuntime, 'function');
 });
 
+test('tab runtime caps per-attempt response timeout to the remaining resilient timeout budget', () => {
+  const source = fs.readFileSync('background/tab-runtime.js', 'utf8');
+  const globalScope = {};
+  const api = new Function('self', `${source}; return self.MultiPageBackgroundTabRuntime;`)(globalScope);
+
+  const runtime = api.createTabRuntime({
+    LOG_PREFIX: '[test]',
+    addLog: async () => {},
+    chrome: {
+      tabs: {
+        get: async () => ({ id: 1, url: 'https://example.com', status: 'complete' }),
+        query: async () => [],
+      },
+    },
+    getSourceLabel: (source) => source || 'unknown',
+    getState: async () => ({ tabRegistry: {}, sourceLastUrls: {} }),
+    matchesSourceUrlFamily: () => false,
+    normalizeLocalCpaStep9Mode: () => 'submit',
+    parseUrlSafely: () => null,
+    registerTab: async () => {},
+    setState: async () => {},
+    shouldBypassStep9ForLocalCpa: () => false,
+    throwIfStopped: () => {},
+  });
+
+  assert.equal(
+    runtime.resolveResponseTimeoutMs({ type: 'PREPARE_SIGNUP_VERIFICATION' }, undefined, 30000),
+    30000
+  );
+  assert.equal(
+    runtime.resolveResponseTimeoutMs({ type: 'PREPARE_SIGNUP_VERIFICATION' }, 12000, 5000),
+    5000
+  );
+});
+
 test('tab runtime waitForTabComplete waits until tab status becomes complete', async () => {
   const source = fs.readFileSync('background/tab-runtime.js', 'utf8');
   const globalScope = {};
diff --git a/项目完整链路说明.md b/项目完整链路说明.md
index 366d38e..9211912 100644
--- a/项目完整链路说明.md
+++ b/项目完整链路说明.md
@@ -312,6 +312,7 @@
 6. 上报完成后再异步点击提交，避免页面跳转打断响应通道
 7. 延迟提交真正触发前会再次检查 Stop 状态，避免用户已停止时页面仍继续自动提交
 8. 后台在真正确认 Step 3 完成前，会额外检查提交后是否切换页面；如果出现认证页 `Try again / 重试` 页面，或 `/email-verification` 上的 `405 / Route Error` 重试页，会先通过共享恢复逻辑最多自动点击 5 次 `重试` 尝试恢复，再继续后续链路
+9. Step 3 收尾阶段如果页面切换导致旧内容脚本失联，后台会把单次消息等待收口到当前收尾预算内，优先尽快重试重连；若最终仍未恢复，则输出中文的步骤级错误，而不是直接暴露底层英文通信超时
 
 ### Step 4 / Step 8