Preserve stable snapshots and stabilize Electron e2e (#734)

src/stores/chat/history-actions.ts

@@ -37,7 +37,45 @@ export function createHistoryActions(
       const { currentSessionKey } = get();
       if (!quiet) set({ loading: true, error: null });
 
+      const isCurrentSession = () => get().currentSessionKey === currentSessionKey;
+      const getPreviewMergeKey = (message: RawMessage): string => (
+        `${message.id ?? ''}|${message.role}|${message.timestamp ?? ''}|${getMessageText(message.content)}`
+      );
+      const mergeHydratedMessages = (
+        currentMessages: RawMessage[],
+        hydratedMessages: RawMessage[],
+      ): RawMessage[] => {
+        const hydratedFilesByKey = new Map(
+          hydratedMessages
+            .filter((message) => message._attachedFiles?.length)
+            .map((message) => [
+              getPreviewMergeKey(message),
+              message._attachedFiles!.map((file) => ({ ...file })),
+            ]),
+        );
+
+        return currentMessages.map((message) => {
+          const attachedFiles = hydratedFilesByKey.get(getPreviewMergeKey(message));
+          return attachedFiles
+            ? { ...message, _attachedFiles: attachedFiles }
+            : message;
+        });
+      };
+
+      const applyLoadFailure = (errorMessage: string | null) => {
+        if (!isCurrentSession()) return;
+        set((state) => {
+          const hasMessages = state.messages.length > 0;
+          return {
+            loading: false,
+            error: !quiet && errorMessage ? errorMessage : state.error,
+            ...(hasMessages ? {} : { messages: [] as RawMessage[] }),
+          };
+        });
+      };
+
       const applyLoadedMessages = (rawMessages: RawMessage[], thinkingLevel: string | null) => {
+        if (!isCurrentSession()) return;
         // Before filtering: attach images/files from tool_result messages to the next assistant message
         const messagesWithToolImages = enrichWithToolResultFiles(rawMessages);
         const filteredMessages = messagesWithToolImages.filter((msg) => !isToolResultRole(msg.role) && !isInternalMessage(msg));
@@ -95,17 +133,11 @@ export function createHistoryActions(
 
         // Async: load missing image previews from disk (updates in background)
         loadMissingPreviews(finalMessages).then((updated) => {
+          if (!isCurrentSession()) return;
           if (updated) {
-            // Create new object references so React.memo detects changes.
-            // loadMissingPreviews mutates AttachedFileMeta in place, so we
-            // must produce fresh message + file references for each affected msg.
-            set({
-              messages: finalMessages.map(msg =>
-                msg._attachedFiles
-                  ? { ...msg, _attachedFiles: msg._attachedFiles.map(f => ({ ...f })) }
-                  : msg
-              ),
-            });
+            set((state) => ({
+              messages: mergeHydratedMessages(state.messages, finalMessages),
+            }));
           }
         });
         const { pendingFinal, lastUserMessageAt, sending: isSendingNow } = get();
@@ -163,7 +195,7 @@ export function createHistoryActions(
           if (fallbackMessages.length > 0) {
             applyLoadedMessages(fallbackMessages, null);
           } else {
-            set({ messages: [], loading: false });
+            applyLoadFailure(result.error || 'Failed to load chat history');
           }
         }
       } catch (err) {
@@ -172,7 +204,7 @@ export function createHistoryActions(
         if (fallbackMessages.length > 0) {
           applyLoadedMessages(fallbackMessages, null);
         } else {
-          set({ messages: [], loading: false });
+          applyLoadFailure(String(err));
         }
       }
     },