fix(wechat): guard bare page-continuation follow-ups from session loss and memory drift

Prevent chat-to-page flows like writing a poem then saying "做成页面吧" from opening
a fresh session without carried content, failing with a vague error, or letting Memory
page-template preferences replace the immediate topic.

Co-authored-by: Cursor <cursoragent@cursor.com>

wechat-mp.mjs

@@ -44,6 +44,13 @@ import {
   isWechatSessionPageContinuation,
   isWechatContentEditFollowup,
 } from './wechat/intent/page-continuation.mjs';
+import {
+  extractLastSubstantiveAssistantFromConversation,
+  filterMemoryForImmediatePageContext,
+  isWechatPageContinuationRepairableError,
+  shouldFailFastWechatPageContinuation,
+  WECHAT_PAGE_CONTINUATION_MISSING_SOURCE_TEXT,
+} from './wechat/intent/page-continuation-context.mjs';
 import { resolvePageGenerateOutcome } from './wechat/handlers/page-generate.mjs';
 import {
   MEMORY_V2_PRODUCT_EVENT_TYPES,
@@ -231,6 +238,18 @@ function messageVisibleText(message) {
     .join('');
 }
 
+async function fetchLastSubstantiveAssistantFromSession(fetchForSession, sessionId) {
+  if (!sessionId || typeof fetchForSession !== 'function') return '';
+  try {
+    const payload = await readJsonResponse(
+      await fetchForSession(sessionId, `/sessions/${encodeURIComponent(sessionId)}`),
+    );
+    return extractLastSubstantiveAssistantFromConversation(payload?.conversation ?? []);
+  } catch {
+    return '';
+  }
+}
+
 function pushMessage(messages, incoming) {
   const last = messages[messages.length - 1];
   if (last?.id && incoming?.id && last.id === incoming.id) {
@@ -2118,6 +2137,7 @@ export function createWechatMpService({
       await userAuth.getAgentSessionPolicy(userId);
     const publishLayout = await userAuth.getUserPublishLayout(userId);
     const addressName = resolveWechatAddressName(userContext);
+    let carriedSessionContentForNewSession = '';
     const existingRoute = await userAuth.getWechatAgentRoute(config.appId, openid);
     if (existingRoute?.agentSessionId) {
       const now = Date.now();
@@ -2223,7 +2243,25 @@ export function createWechatMpService({
               logger.warn?.('WeChat MP route touch failed:', err);
             });
           }
-          return { sessionId: existingRoute.agentSessionId, isNewSession: false };
+          return {
+            sessionId: existingRoute.agentSessionId,
+            isNewSession: false,
+            carriedSessionContent: '',
+          };
+        }
+        let carriedSessionContent = '';
+        if (retainUnlinkedRoute) {
+          carriedSessionContent = await fetchLastSubstantiveAssistantFromSession(
+            fetchForSession,
+            existingRoute.agentSessionId,
+          );
+          if (carriedSessionContent) {
+            logger.warn?.('WeChat MP retaining prior assistant content after route tool mismatch:', {
+              agentSessionId: existingRoute.agentSessionId,
+              contentLength: carriedSessionContent.length,
+            });
+            carriedSessionContentForNewSession = carriedSessionContent;
+          }
         }
         await userAuth.clearWechatAgentRoute(config.appId, openid);
         rememberedWechatContexts.delete(existingRoute.agentSessionId);
@@ -2304,7 +2342,11 @@ export function createWechatMpService({
       openid,
       agentSessionId: sessionId,
     });
-    return { sessionId, isNewSession: true };
+    return {
+      sessionId,
+      isNewSession: true,
+      carriedSessionContent: carriedSessionContentForNewSession,
+    };
   };
 
   const refreshWechatSessionSnapshot = async (sessionId, userId) => {
@@ -2452,12 +2494,13 @@ export function createWechatMpService({
         ?? messageVisibleText(userMessage),
     ).trim();
     try {
-      const memoryContext = await chatIntentRouter.resolveAgentMemoryContext({
+      const memoryContextRaw = await chatIntentRouter.resolveAgentMemoryContext({
         userId,
         sessionId,
         text: displayText,
         forceDeepReasoning: false,
       });
+      let memoryContext = memoryContextRaw;
       if (
         !memoryContext?.injectionEnabled
         || !Array.isArray(memoryContext.memories)
@@ -2465,6 +2508,15 @@ export function createWechatMpService({
       ) {
         return userMessage;
       }
+      if (preserveAgentPrompt) {
+        memoryContext = {
+          ...memoryContext,
+          memories: filterMemoryForImmediatePageContext(memoryContext.memories),
+        };
+        if (memoryContext.memories.length === 0) {
+          return userMessage;
+        }
+      }
       const memoryCount = memoryContext.memories.length;
       if (mysqlPool?.query) {
         void recordMemoryV2ProductEvent(mysqlPool, {
@@ -2597,6 +2649,7 @@ export function createWechatMpService({
       retainUnlinkedRoute: sessionPageContinuation,
     });
     let sessionId = route.sessionId;
+    let carriedSessionContent = String(route.carriedSessionContent ?? '').trim();
     await ensureSessionProvider(sessionId);
     if (wechatIntent.kind === 'session.reset') {
       await sendCustomerServiceText(
@@ -2607,6 +2660,34 @@ export function createWechatMpService({
       return { sessionId };
     }
     await rememberWechatUserContext(sessionId, user, { forceBootstrap: route.isNewSession });
+    if (
+      wechatIntent.kind === 'page.generate'
+      && sessionPageContinuation
+    ) {
+      const sessionAssistantContent = carriedSessionContent
+        || await fetchLastSubstantiveAssistantFromSession(fetchForSession, sessionId);
+      if (
+        shouldFailFastWechatPageContinuation({
+          sessionPageContinuation,
+          userText: resetCandidate,
+          carriedSessionContent,
+          sessionAssistantContent,
+        })
+      ) {
+        const text = WECHAT_PAGE_CONTINUATION_MISSING_SOURCE_TEXT;
+        try {
+          await sendWechatFailureNotice(inbound.fromUserName, text, user, {
+            sourceMsgId: intent.msgId,
+          });
+        } catch (sendErr) {
+          logger.error?.('WeChat MP page continuation missing-source notice failed:', sendErr);
+        }
+        throw markWechatUserNotified(new Error(text));
+      }
+      if (!carriedSessionContent && sessionAssistantContent) {
+        carriedSessionContent = sessionAssistantContent;
+      }
+    }
     let finished = false;
     let progressTimer = null;
     const skipProgressReply =
@@ -2641,6 +2722,7 @@ export function createWechatMpService({
               wantsDocx: wechatIntent.wantsDocx,
               imagePolicy,
               preferImmediateContext: sessionPageContinuation,
+              carriedSessionContent,
             })
           : buildWechatAgentPrompt(intent, {
               imagePolicy,
@@ -2765,6 +2847,14 @@ export function createWechatMpService({
             },
           });
           if (pageOutcome.action === 'session_retry') {
+            if (sessionPageContinuation && pageAttempt < maxImmediateContextPageAttempts) {
+              logger.warn?.('WeChat MP immediate-context fake delivery repair retry:', {
+                sessionId,
+                userId: user.userId,
+                pageAttempt,
+              });
+              continue;
+            }
             throw new Error('stale_session_poisoned_completion');
           }
           if (pageOutcome.action === 'fail') {
@@ -2987,6 +3077,22 @@ export function createWechatMpService({
         sessionId
         && (isRecoverableWechatAgentSessionError(message) || isWechatAgentApiErrorText(message));
       if (mayBeStaleSession) {
+        if (sessionPageContinuation && isWechatPageContinuationRepairableError(message)) {
+          const text = buildPagePublishFailureText();
+          await userAuth.clearWechatAgentRoute(config.appId, inbound.fromUserName).catch((clearErr) => {
+            logger.warn?.('WeChat MP page continuation repair route clear failed:', clearErr);
+          });
+          try {
+            await sendWechatFailureNotice(inbound.fromUserName, text, user, {
+              sourceMsgId: intent.msgId,
+            });
+          } catch (sendErr) {
+            logger.error?.('WeChat MP page continuation repair notice failed:', sendErr);
+          }
+          const repairError = markWechatUserNotified(new Error(text));
+          repairError.wechatAgentSessionId = sessionId;
+          throw repairError;
+        }
         if (sessionPageContinuation) {
           await userAuth.clearWechatAgentRoute(config.appId, inbound.fromUserName).catch((clearErr) => {
             logger.warn?.('WeChat MP contextual follow-up route clear failed:', clearErr);
@@ -3021,6 +3127,7 @@ export function createWechatMpService({
                 wantsDocx: wechatIntent.wantsDocx,
                 imagePolicy,
                 preferImmediateContext: sessionPageContinuation,
+                carriedSessionContent,
               })
             : buildWechatAgentPrompt(intent, {
                 imagePolicy,