feat(FN-2394): add Fusion reinstall flow for Pi extensions

- Add dashboard route and server handling to reinstall the Fusion Pi extension
- Introduce a client API helper and wire a reinstall action into PiExtensionsManager
- Polish action spacing and document Fusion reinstall recovery in the CLI README
- Expand route, API, and component tests including reinstall refresh stability coverage
- Add a changeset for @runfusion/fusion patch release

packages/dashboard/app/api.test.ts

@@ -55,6 +55,7 @@ import {
   fetchPiSettings,
   updatePiSettings,
   installPiPackage,
+  reinstallFusionPiPackage,
   fetchPiExtensions,
   updatePiExtensions,
   fetchProjectTasks,
@@ -5962,6 +5963,45 @@ describe("installPiPackage", () => {
   });
 });
 
+describe("reinstallFusionPiPackage", () => {
+  const originalFetch = globalThis.fetch;
+
+  afterEach(() => {
+    globalThis.fetch = originalFetch;
+  });
+
+  it("sends POST to /api/pi-settings/reinstall-fusion", async () => {
+    globalThis.fetch = vi.fn().mockReturnValue(
+      mockFetchResponse(true, { success: true, source: "npm:@runfusion/fusion" })
+    );
+
+    const result = await reinstallFusionPiPackage();
+
+    expect(result).toEqual({ success: true, source: "npm:@runfusion/fusion" });
+    expect(globalThis.fetch).toHaveBeenCalledWith("/api/pi-settings/reinstall-fusion", expect.objectContaining({
+      method: "POST",
+    }));
+  });
+
+  it("forwards projectId query parameter when provided", async () => {
+    globalThis.fetch = vi.fn().mockReturnValue(
+      mockFetchResponse(true, { success: true, source: "npm:@runfusion/fusion" })
+    );
+
+    await reinstallFusionPiPackage("proj-123");
+
+    expect(globalThis.fetch).toHaveBeenCalledWith("/api/pi-settings/reinstall-fusion?projectId=proj-123", expect.objectContaining({
+      method: "POST",
+    }));
+  });
+
+  it("throws API error message on failure", async () => {
+    globalThis.fetch = vi.fn().mockReturnValue(mockFetchResponse(false, { error: "Reinstall failed" }, 500));
+
+    await expect(reinstallFusionPiPackage()).rejects.toThrow("Reinstall failed");
+  });
+});
+
 describe("fetchPiExtensions", () => {
   const originalFetch = globalThis.fetch;
 

packages/dashboard/app/api.ts

@@ -657,6 +657,13 @@ export async function installPiPackage(source: string): Promise<{ success: boole
   });
 }
 
+/** Reinstall Fusion's bundled pi package and ensure it remains in global Pi settings. */
+export async function reinstallFusionPiPackage(projectId?: string): Promise<{ success: boolean; source: string }> {
+  return api<{ success: boolean; source: string }>(withProjectId("/pi-settings/reinstall-fusion", projectId), {
+    method: "POST",
+  });
+}
+
 export async function uploadAttachment(id: string, file: File, projectId?: string): Promise<TaskAttachment> {
   const formData = new FormData();
   formData.append("file", file);

packages/dashboard/app/components/PiExtensionsManager.tsx

@@ -26,7 +26,7 @@ import {
   RefreshCw,
   Trash2,
 } from "lucide-react";
-import { fetchPiSettings, updatePiSettings, installPiPackage, fetchPiExtensions, updatePiExtensions, type PiSettings, type PiExtensionEntry } from "../api";
+import { fetchPiSettings, updatePiSettings, installPiPackage, reinstallFusionPiPackage, fetchPiExtensions, updatePiExtensions, type PiSettings, type PiExtensionEntry } from "../api";
 import type { ToastType } from "../hooks/useToast";
 
 interface PiExtensionsManagerProps {
@@ -67,6 +67,7 @@ export function PiExtensionsManager({ addToast, projectId }: PiExtensionsManager
   const [settings, setSettings] = useState<PiSettings | null>(null);
   const [loading, setLoading] = useState(true);
   const [installing, setInstalling] = useState(false);
+  const [reinstallingFusion, setReinstallingFusion] = useState(false);
   const [newSource, setNewSource] = useState("");
   const [expandedPackages, setExpandedPackages] = useState<Set<number>>(new Set());
 
@@ -154,6 +155,19 @@ export function PiExtensionsManager({ addToast, projectId }: PiExtensionsManager
     }
   };
 
+  const handleReinstallFusion = async () => {
+    try {
+      setReinstallingFusion(true);
+      await reinstallFusionPiPackage(projectId);
+      await Promise.all([loadSettings(), loadExtensions()]);
+      addToast("Fusion skill reinstalled successfully", "success");
+    } catch (err) {
+      addToast(`Failed to reinstall Fusion skill: ${err instanceof Error ? err.message : String(err)}`, "error");
+    } finally {
+      setReinstallingFusion(false);
+    }
+  };
+
   const handleRemovePackage = async (sourceToRemove: string) => {
     if (!settings) return;
 
@@ -263,6 +277,15 @@ export function PiExtensionsManager({ addToast, projectId }: PiExtensionsManager
                 {installing ? "Installing…" : "Add"}
               </button>
             </div>
+            <div className="pi-ext-add-form-row">
+              <button
+                className="btn"
+                onClick={handleReinstallFusion}
+                disabled={reinstallingFusion}
+              >
+                {reinstallingFusion ? "Reinstalling Fusion…" : "Reinstall Fusion skill"}
+              </button>
+            </div>
           </div>
 
           {/* Package list */}

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

@@ -7,6 +7,7 @@ import { PiExtensionsManager } from "../PiExtensionsManager";
 const mockFetchPiSettings = vi.fn();
 const mockUpdatePiSettings = vi.fn();
 const mockInstallPiPackage = vi.fn();
+const mockReinstallFusionPiPackage = vi.fn();
 const mockFetchPiExtensions = vi.fn();
 const mockUpdatePiExtensions = vi.fn();
 
@@ -53,6 +54,7 @@ vi.mock("../../api", () => ({
   fetchPiSettings: (...args: unknown[]) => mockFetchPiSettings(...args),
   updatePiSettings: (...args: unknown[]) => mockUpdatePiSettings(...args),
   installPiPackage: (...args: unknown[]) => mockInstallPiPackage(...args),
+  reinstallFusionPiPackage: (...args: unknown[]) => mockReinstallFusionPiPackage(...args),
   fetchPiExtensions: (...args: unknown[]) => mockFetchPiExtensions(...args),
   updatePiExtensions: (...args: unknown[]) => mockUpdatePiExtensions(...args),
 }));
@@ -91,6 +93,7 @@ describe("PiExtensionsManager", () => {
     // Default mock for fetchPiExtensions to return empty settings
     mockFetchPiExtensions.mockResolvedValue({ extensions: [], disabledIds: [], settingsPath: "" });
     mockUpdatePiExtensions.mockResolvedValue({ extensions: [], disabledIds: [], settingsPath: "" });
+    mockReinstallFusionPiPackage.mockResolvedValue({ success: true, source: "npm:@runfusion/fusion" });
   });
 
   describe("Rendering", () => {
@@ -113,6 +116,15 @@ describe("PiExtensionsManager", () => {
       });
     });
 
+    it("renders reinstall Fusion skill action", async () => {
+      mockFetchPiSettings.mockResolvedValueOnce(mockPiSettings);
+      render(<PiExtensionsManager addToast={addToast} />);
+
+      await waitFor(() => {
+        expect(screen.getByRole("button", { name: "Reinstall Fusion skill" })).toBeTruthy();
+      });
+    });
+
     it("renders package list with source badges", async () => {
       mockFetchPiSettings.mockResolvedValueOnce(mockPiSettings);
       render(<PiExtensionsManager addToast={addToast} />);
@@ -268,6 +280,55 @@ describe("PiExtensionsManager", () => {
     });
   });
 
+  describe("Reinstall Fusion action", () => {
+    it("calls reinstall API and refreshes settings and extensions on success", async () => {
+      mockFetchPiSettings.mockResolvedValue(mockPiSettings);
+      mockFetchPiExtensions.mockResolvedValue({ extensions: [], disabledIds: [], settingsPath: "" });
+      mockReinstallFusionPiPackage.mockResolvedValueOnce({ success: true, source: "npm:@runfusion/fusion" });
+
+      render(<PiExtensionsManager addToast={addToast} projectId="proj-123" />);
+
+      await waitFor(() => {
+        expect(screen.getByRole("button", { name: "Reinstall Fusion skill" })).toBeTruthy();
+      });
+
+      const settingsCallsBefore = mockFetchPiSettings.mock.calls.length;
+      const extensionCallsBefore = mockFetchPiExtensions.mock.calls.length;
+
+      await userEvent.click(screen.getByRole("button", { name: "Reinstall Fusion skill" }));
+
+      await waitFor(() => {
+        expect(mockReinstallFusionPiPackage).toHaveBeenCalledWith("proj-123");
+      });
+      await waitFor(() => {
+        expect(mockFetchPiSettings.mock.calls.length).toBeGreaterThan(settingsCallsBefore);
+        expect(mockFetchPiExtensions.mock.calls.length).toBeGreaterThan(extensionCallsBefore);
+      });
+      expect(addToast).toHaveBeenCalledWith("Fusion skill reinstalled successfully", "success");
+    });
+
+    it("shows error toast and resets loading state when reinstall fails", async () => {
+      mockFetchPiSettings.mockResolvedValue(mockPiSettings);
+      mockReinstallFusionPiPackage.mockRejectedValueOnce(new Error("Boom"));
+
+      render(<PiExtensionsManager addToast={addToast} />);
+
+      await waitFor(() => {
+        expect(screen.getByRole("button", { name: "Reinstall Fusion skill" })).toBeTruthy();
+      });
+
+      await userEvent.click(screen.getByRole("button", { name: "Reinstall Fusion skill" }));
+
+      await waitFor(() => {
+        expect(addToast).toHaveBeenCalledWith("Failed to reinstall Fusion skill: Boom", "error");
+      });
+
+      await waitFor(() => {
+        expect(screen.getByRole("button", { name: "Reinstall Fusion skill" })).toBeTruthy();
+      });
+    });
+  });
+
   describe("Remove package", () => {
     it("calls updatePiSettings with package removed from list", async () => {
       mockFetchPiSettings.mockResolvedValueOnce(mockPiSettings);

packages/dashboard/app/styles.css

@@ -36549,6 +36549,9 @@ html .column.drag-over * {
 }
 
 .pi-ext-add-form {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-sm);
   margin-bottom: var(--space-md);
 }