refactor(frontend/builder): address review comments in BuilderChatPanel

- Remove useCallback from handleApplyAction (violates AGENTS.md)
- Import TEXTAREA_MAX_LENGTH from PanelInput instead of duplicating constant
- Remove dead @tanstack/react-query mock and associated invalidateQueries test

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

@@ -52,11 +52,6 @@ vi.mock("@/services/environment", () => ({
   environment: { getAGPTServerBaseUrl: () => "http://localhost:8000" },
 }));
 
-const mockInvalidateQueries = vi.fn();
-vi.mock("@tanstack/react-query", () => ({
-  useQueryClient: () => ({ invalidateQueries: mockInvalidateQueries }),
-}));
-
 const mockToast = vi.fn();
 vi.mock("@/components/molecules/Toast/use-toast", () => ({
   useToast: () => ({ toast: mockToast }),
@@ -108,7 +103,6 @@ beforeEach(() => {
   mockSetNodes.mockClear();
   mockSetEdges.mockClear();
   mockPostV2CreateSession.mockClear();
-  mockInvalidateQueries.mockClear();
   mockSendMessage.mockClear();
   mockSetMessages.mockClear();
   mockToast.mockClear();
@@ -428,29 +422,6 @@ describe("useBuilderChatPanel – flowID reset", () => {
   });
 });
 
-describe("useBuilderChatPanel – apply does not trigger cache refetch", () => {
-  it("does NOT call invalidateQueries after applying an update_node_input action (prevents refetch overwriting local state)", () => {
-    mockNodes.push({
-      id: "n1",
-      data: { hardcodedValues: { existing: "val" } },
-    });
-    mockFlowID = "flow-cache";
-
-    const { result } = renderHook(() => useBuilderChatPanel());
-
-    act(() => {
-      result.current.handleApplyAction({
-        type: "update_node_input",
-        nodeId: "n1",
-        key: "query",
-        value: "new val",
-      });
-    });
-
-    expect(mockInvalidateQueries).not.toHaveBeenCalled();
-  });
-});
-
 describe("useBuilderChatPanel – handleApplyAction", () => {
   it("update_node_input: calls setNodes with merged hardcodedValues (bypasses history)", () => {
     mockNodes.push({

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

@@ -7,7 +7,6 @@ import { DefaultChatTransport } from "ai";
 import {
   type KeyboardEvent,
   type RefObject,
-  useCallback,
   useEffect,
   useMemo,
   useRef,
@@ -31,12 +30,10 @@ import {
   parseGraphActions,
   serializeGraphForChat,
 } from "./helpers";
+import { TEXTAREA_MAX_LENGTH } from "./components/PanelInput";
 
 type SendMessageFn = ReturnType<typeof useChat>["sendMessage"];
 
-/** Maximum characters accepted by `sendRawMessage`, mirroring the textarea `maxLength`. */
-const MAX_RAW_MESSAGE_LENGTH = 4000;
-
 /**
  * Per-graph session cache with a simple LRU cap.
  * Maps flowID → sessionId so the same chat session is reused each time the
@@ -452,35 +449,32 @@ export function useBuilderChatPanel({
     }
   }
 
-  const handleApplyAction = useCallback(
-    (action: GraphAction) => {
-      const deps: ApplyActionDeps = {
-        toast,
-        setNodes,
-        setEdges,
-        setUndoStack,
-        setAppliedActionKeys,
-      };
-      let applied = false;
-      if (action.type === "update_node_input") {
-        applied = applyUpdateNodeInput(action, deps);
-      } else if (action.type === "connect_nodes") {
-        applied = applyConnectNodes(action, deps);
-      } else {
-        // Exhaustiveness guard — TypeScript ensures all GraphAction types are handled above.
-        const _: never = action;
-        void _;
-      }
-      if (applied) {
-        setAppliedActionKeys((prev) => {
-          const next = new Set(prev);
-          next.add(getActionKey(action));
-          return next;
-        });
-      }
-    },
-    [toast, setNodes, setEdges],
-  );
+  function handleApplyAction(action: GraphAction) {
+    const deps: ApplyActionDeps = {
+      toast,
+      setNodes,
+      setEdges,
+      setUndoStack,
+      setAppliedActionKeys,
+    };
+    let applied = false;
+    if (action.type === "update_node_input") {
+      applied = applyUpdateNodeInput(action, deps);
+    } else if (action.type === "connect_nodes") {
+      applied = applyConnectNodes(action, deps);
+    } else {
+      // Exhaustiveness guard — TypeScript ensures all GraphAction types are handled above.
+      const _: never = action;
+      void _;
+    }
+    if (applied) {
+      setAppliedActionKeys((prev) => {
+        const next = new Set(prev);
+        next.add(getActionKey(action));
+        return next;
+      });
+    }
+  }
 
   function handleUndoLastAction() {
     // Read the current stack directly rather than inside the setUndoStack updater.
@@ -502,8 +496,8 @@ export function useBuilderChatPanel({
   function sendRawMessage(text: string) {
     if (!text || !canSend) return;
     const trimmed =
-      text.length > MAX_RAW_MESSAGE_LENGTH
-        ? text.slice(0, MAX_RAW_MESSAGE_LENGTH)
+      text.length > TEXTAREA_MAX_LENGTH
+        ? text.slice(0, TEXTAREA_MAX_LENGTH)
         : text;
     sendMessage({ text: trimmed });
   }