feat(FN-2032): gate Header nodes button by nodesView flag

- Add optional showNodesButton prop to Header while keeping default behavior backward compatible
- Hide desktop and mobile overflow Nodes actions when showNodesButton is false
- Wire App.tsx to experimentalFeatures.nodesView, guard node toggle handling, and auto-close the overlay when disabled
- Add Header tests for desktop/mobile visibility and click behavior across showNodesButton states

packages/dashboard/app/App.tsx

@@ -197,6 +197,14 @@ function AppInner() {
   } = useAppSettings(currentProject?.id);
 
   const skillsEnabled = experimentalFeatures.skillsView === true;
+  const nodesEnabled = experimentalFeatures.nodesView === true;
+
+  // Auto-close nodes overlay if feature flag is toggled off while overlay is open
+  useEffect(() => {
+    if (nodesOpen && !nodesEnabled) {
+      setNodesOpen(false);
+    }
+  }, [nodesOpen, nodesEnabled]);
   const {
     availableModels,
     favoriteProviders,
@@ -275,8 +283,9 @@ function AppInner() {
   }, [modalManager]);
 
   const handleOpenNodes = useCallback(() => {
+    if (!nodesEnabled) return;
     setNodesOpen((prev) => !prev);
-  }, []);
+  }, [nodesEnabled]);
 
   const handleOpenMissionsView = useCallback(() => {
     setMissionTargetId(undefined);
@@ -547,6 +556,7 @@ function AppInner() {
         onOpenSchedules={modalManager.openSchedules}
         onOpenGitManager={modalManager.openGitManager}
         onOpenNodes={handleOpenNodes}
+        showNodesButton={nodesEnabled}
         onOpenWorkflowSteps={modalManager.openWorkflowSteps}
         onOpenScripts={modalManager.openScripts}
         onRunScript={modalManager.runScript}

packages/dashboard/app/components/Header.tsx

@@ -170,6 +170,8 @@ export interface HeaderProps {
   onOpenSchedules?: () => void;
   onOpenGitManager?: () => void;
   onOpenNodes?: () => void;
+  /** When false, hides the Nodes management button. Defaults to true for backward compat. */
+  showNodesButton?: boolean;
   onOpenWorkflowSteps?: () => void;
   onOpenScripts?: () => void;
   onRunScript?: (name: string, command: string) => void;
@@ -219,6 +221,7 @@ export function Header({
   onOpenSchedules,
   onOpenGitManager,
   onOpenNodes,
+  showNodesButton,
   onOpenWorkflowSteps,
   onOpenScripts,
   onRunScript,
@@ -878,7 +881,7 @@ export function Header({
         )}
 
         {/* Nodes button - desktop only (moved to overflow on mobile/tablet) */}
-        {!isCompact && onOpenNodes && (
+        {!isCompact && onOpenNodes && showNodesButton !== false && (
           <button
             className="btn-icon"
             onClick={onOpenNodes}
@@ -1015,7 +1018,7 @@ export function Header({
               </button>
             )}
             {/* Nodes - in overflow on mobile */}
-            {onOpenNodes && (
+            {onOpenNodes && showNodesButton !== false && (
               <button
                 className="mobile-overflow-item"
                 onClick={() => handleOverflowAction(onOpenNodes)}

packages/dashboard/app/components/__tests__/Header.test.tsx

@@ -1648,4 +1648,57 @@ describe("Header", () => {
       expect(slot).toBeNull();
     });
   });
+
+  describe("Nodes button visibility", () => {
+    describe("desktop viewport", () => {
+      it("shows nodes button by default when onOpenNodes is provided without showNodesButton", () => {
+        render(<Header onOpenSettings={vi.fn()} onOpenNodes={vi.fn()} />);
+        expect(screen.getByTestId("nodes-btn")).toBeDefined();
+      });
+
+      it("shows nodes button when showNodesButton is true and onOpenNodes is provided", () => {
+        render(<Header onOpenSettings={vi.fn()} onOpenNodes={vi.fn()} showNodesButton={true} />);
+        expect(screen.getByTestId("nodes-btn")).toBeDefined();
+      });
+
+      it("hides nodes button when showNodesButton is false", () => {
+        render(<Header onOpenSettings={vi.fn()} onOpenNodes={vi.fn()} showNodesButton={false} />);
+        expect(screen.queryByTestId("nodes-btn")).toBeNull();
+      });
+
+      it("calls onOpenNodes when nodes button is clicked", () => {
+        const onOpenNodes = vi.fn();
+        render(<Header onOpenSettings={vi.fn()} onOpenNodes={onOpenNodes} />);
+        fireEvent.click(screen.getByTestId("nodes-btn"));
+        expect(onOpenNodes).toHaveBeenCalledOnce();
+      });
+    });
+
+    describe("mobile viewport", () => {
+      beforeEach(() => {
+        mockMatchMedia("mobile");
+      });
+
+      it("hides mobile overflow nodes button when showNodesButton is false", () => {
+        render(<Header onOpenSettings={vi.fn()} onOpenNodes={vi.fn()} showNodesButton={false} />);
+        // Open the overflow menu to check mobile overflow items
+        fireEvent.click(screen.getByTitle("More header actions"));
+        expect(screen.queryByTestId("overflow-nodes-btn")).toBeNull();
+      });
+
+      it("shows mobile overflow nodes button by default when onOpenNodes is provided", () => {
+        render(<Header onOpenSettings={vi.fn()} onOpenNodes={vi.fn()} />);
+        // Open the overflow menu to check mobile overflow items
+        fireEvent.click(screen.getByTitle("More header actions"));
+        expect(screen.getByTestId("overflow-nodes-btn")).toBeDefined();
+      });
+
+      it("shows mobile overflow nodes button when showNodesButton is true", () => {
+        render(<Header onOpenSettings={vi.fn()} onOpenNodes={vi.fn()} showNodesButton={true} />);
+        // Open the overflow menu to check mobile overflow items
+        fireEvent.click(screen.getByTitle("More header actions"));
+        expect(screen.getByTestId("overflow-nodes-btn")).toBeDefined();
+      });
+    });
+  });
 });