fix(frontend/builder): clear stale messages in retrySession so new session starts clean

autogpt_platform/frontend/src/app/(platform)/build/components/BuilderChatPanel/__tests__/useBuilderChatPanel.test.ts

@@ -885,6 +885,29 @@ describe("useBuilderChatPanel – retrySession", () => {
     expect(result.current.sessionId).toBe("sess-retry-seed");
     expect(mockSendMessage).toHaveBeenCalledOnce();
   });
+
+  it("clears stale messages when retrySession is called (setMessages reset)", async () => {
+    // Simulate stale messages from a previous session
+    mockChatMessages = [
+      {
+        id: "stale-1",
+        role: "assistant",
+        parts: [{ type: "text", text: "Old message from failed session" }],
+      },
+    ];
+
+    const { result } = renderHook(() => useBuilderChatPanel());
+
+    // Messages should be present before retry (from mock)
+    expect(result.current.messages).toHaveLength(1);
+
+    act(() => {
+      result.current.retrySession();
+    });
+
+    // setMessages([]) clears the internal useChat message list
+    expect(mockSetMessages).toHaveBeenCalledWith([]);
+  });
 });
 
 describe("useBuilderChatPanel – handleSend", () => {

autogpt_platform/frontend/src/app/(platform)/build/components/BuilderChatPanel/useBuilderChatPanel.ts

@@ -346,12 +346,15 @@ export function useBuilderChatPanel({
   // hasSentSeedMessageRef is reset so the seed message is re-sent to the
   // new session (it may have been set to true by a previous successful session
   // that was later invalidated without a flowID change).
+  // Messages are cleared so stale messages from the previous session are not
+  // shown alongside content from the new session.
   function retrySession() {
     if (flowID) graphSessionCache.delete(flowID);
     setSessionId(null);
     setSessionError(false);
     isCreatingSessionRef.current = false;
     hasSentSeedMessageRef.current = false;
+    setMessages([]);
   }
 
   function handleSend() {