fix(canvas): prevent stale autosaves from overwriting generated images

components/canvas/CanvasChatPanel.tsx

@@ -15320,17 +15320,40 @@ export function CanvasChatPanel({
   }, [activeChatSessionMode, startNewChatSession]);
 
   const switchToSession = useCallback((sessionId: string) => {
-    if (!sessionId || sessionId === activeChatId) {
+    if (!sessionId) {
       setIsSessionMenuOpen(false);
       return;
     }
+    if (sessionId === activeChatId) {
+      setIsSessionMenuOpen(false);
+      if (status === "streaming" || status === "submitted" || isClawdSubmitting) return;
+      // Reopening the current conversation must recover an empty/stale view too.
+      void mutateHistoryData().then((fresh) => {
+        if (
+          activeChatIdRef.current !== sessionId ||
+          inFlightChatIdRef.current === sessionId ||
+          !Array.isArray(fresh?.messages)
+        ) return;
+        loadedHistorySignatureRef.current = buildCanvasHistoryMessagesSignature(
+          toRawCanvasChatId(sessionId), fresh.messages
+        );
+        processedMessageIds.current.clear();
+        hasHydratedHistoryRef.current = true;
+        setMessages(sortCanvasMessagesByCreatedAt(fresh.messages));
+        setMessageViewportKey((previous) => previous + 1);
+      }).catch((error) => {
+        console.error("[CanvasChat] Failed to reopen current conversation:", error);
+        toast.error("聊天记录暂时读取失败，请重试");
+      });
+      return;
+    }
     forceHistoryHydrationRef.current = toRawCanvasChatId(sessionId);
     releaseSendGuard(activeChatId);
     setActiveChatId(sessionId);
     replaceChatSessionQuery(sessionId);
     setIsSessionMenuOpen(false);
     toast.success("已切换聊天窗口");
-  }, [activeChatId, releaseSendGuard, replaceChatSessionQuery]);
+  }, [activeChatId, isClawdSubmitting, mutateHistoryData, releaseSendGuard, replaceChatSessionQuery, setMessages, status]);
 
   const switchToClawdHistorySession = useCallback(
     (historyItem: ClawdHistoryItem) => {

services/canvas/index.ts

@@ -306,26 +306,10 @@ export const canvasService = {
         return response;
       };
 
-      let response = await doSaveWithRateLimitRetry(buildRequestBody(options));
-      let data = await response.json().catch(() => ({}));
-
-      const serverRevision = normalizeRevisionText(data?.canvasUpdatedAt);
-      if (
-        response.status === 409 &&
-        data?.code === "STALE_CANVAS_REVISION" &&
-        serverRevision
-      ) {
-        response = await doSaveWithRateLimitRetry(
-          buildRequestBody(
-            {
-              baseCanvasRevision: serverRevision,
-              baseCanvasUpdatedAt: serverRevision,
-            },
-            false
-          )
-        );
-        data = await response.json().catch(() => ({}));
-      }
+      const response = await doSaveWithRateLimitRetry(buildRequestBody(options));
+      const data = await response.json().catch(() => ({}));
+      // A conflict means this snapshot missed a remote edit. Reusing the newer
+      // revision with the same old nodes would overwrite generated results.
 
       if (!response.ok) {
         return {

tests/routes/canvas-chat-helpers.test.ts

@@ -896,12 +896,16 @@ test.describe("canvas chat pure helpers", () => {
     }
   });
 
-  test("canvas service automatically retries stale save conflicts", async () => {
+  test("stale autosaves cannot overwrite a remotely generated image by adopting its revision", async () => {
     const originalFetch = globalThis.fetch;
     const hadWindow = Object.prototype.hasOwnProperty.call(globalThis, "window");
     const originalWindow = (globalThis as typeof globalThis & { window?: unknown })
       .window;
     const bodies: Array<Record<string, unknown>> = [];
+    let remoteNodes = [{ id: "new-generated-image", type: "image" }];
+    useCanvasStore.getState().setCanvasRevision(
+      "2026-06-22T00:01:00.000Z", "2026-06-22T00:01:00.000Z"
+    );
     const responses = [
       {
         ok: false,
@@ -929,7 +933,9 @@ test.describe("canvas chat pure helpers", () => {
       writable: true,
     });
     globalThis.fetch = (async (_input: RequestInfo | URL, init?: RequestInit) => {
-      bodies.push(JSON.parse(String(init?.body || "{}")));
+      const body = JSON.parse(String(init?.body || "{}"));
+      bodies.push(body);
+      if (bodies.length > 1) remoteNodes = body.canvasData.nodes;
       return responses.shift() as Response;
     }) as typeof fetch;
 
@@ -946,16 +952,15 @@ test.describe("canvas chat pure helpers", () => {
       );
 
       expect(result).toMatchObject({
-        success: true,
-        data: { updatedAt: "2026-06-22T00:02:01.000Z" },
-      });
-      expect(bodies).toHaveLength(2);
-      expect(bodies[1]).toMatchObject({
-        baseCanvasRevision: "2026-06-22T00:02:00.000Z",
-        baseCanvasUpdatedAt: "2026-06-22T00:02:00.000Z",
+        success: false,
+        status: 409,
+        code: "STALE_CANVAS_REVISION",
+        canvasUpdatedAt: "2026-06-22T00:02:00.000Z",
       });
+      expect(bodies).toHaveLength(1);
+      expect(remoteNodes).toEqual([{ id: "new-generated-image", type: "image" }]);
       expect(useCanvasStore.getState().canvasRevision).toBe(
-        "2026-06-22T00:02:01.000Z"
+        "2026-06-22T00:01:00.000Z"
       );
     } finally {
       globalThis.fetch = originalFetch;
@@ -968,6 +973,7 @@ test.describe("canvas chat pure helpers", () => {
       } else {
         Reflect.deleteProperty(globalThis, "window");
       }
+      useCanvasStore.getState().setCanvasRevision(null, null);
     }
   });