FN-5886: show empty usage state after empty fetch

Handle empty usage responses without leaving the panel in its loading skeleton.

- add a hasFetched flag to useUsageData so the UI can distinguish initial loading from an empty completed response
- update UsageIndicator to render the skeleton only before the first fetch completes and show the empty state afterward
- refresh dashboard hook and component tests to cover empty fetches, refresh behavior, and the new loading semantics

Files changed:
 .../dashboard/app/components/UsageIndicator.tsx    |  19 +-
 .../components/__tests__/UsageIndicator.test.tsx   | 395 +++++++++++----------
 .../app/hooks/__tests__/useUsageData.test.ts       |  42 ++-
 packages/dashboard/app/hooks/useUsageData.ts       |   5 +
 4 files changed, 245 insertions(+), 216 deletions(-)

Fusion-Task-Id: FN-5886

Fusion-Task-Lineage: 8fa901a9-3167-4e33-a082-e5de95f692da

packages/dashboard/app/components/UsageIndicator.tsx

@@ -558,7 +558,7 @@ function UsageSkeleton() {
  * reset timers, and pace indicators.
  */
 export function UsageIndicator({ isOpen, onClose, projectId, anchorRect }: UsageIndicatorProps) {
-  const { providers, loading, error, lastUpdated, refresh } = useUsageData({
+  const { providers, loading, error, lastUpdated, hasFetched, refresh } = useUsageData({
     autoRefresh: isOpen, // Only poll when modal is open
   });
 
@@ -581,7 +581,6 @@ export function UsageIndicator({ isOpen, onClose, projectId, anchorRect }: Usage
   const contentRef = useRef<HTMLDivElement>(null);
   const modalRef = useRef<HTMLDivElement>(null);
   const wasOpenRef = useRef(isOpen);
-  const hasCompletedInitialFetchRef = useRef(false);
   const [savedSize, setSavedSize] = useState<ModalSize | null>(() => getSavedModalSize(projectId));
 
   useEffect(() => {
@@ -616,20 +615,6 @@ export function UsageIndicator({ isOpen, onClose, projectId, anchorRect }: Usage
     };
   }, [isOpen, isDesktopViewport, projectId]);
 
-  // Reset initial fetch flag when modal closes to show skeleton on next open
-  useEffect(() => {
-    if (!isOpen) {
-      hasCompletedInitialFetchRef.current = false;
-    }
-  }, [isOpen]);
-
-  // Track when initial fetch completes (providers are populated)
-  useEffect(() => {
-    if (providers.length > 0) {
-      hasCompletedInitialFetchRef.current = true;
-    }
-  }, [providers.length]);
-
   useEffect(() => {
     if (typeof window === "undefined") {
       return;
@@ -923,7 +908,7 @@ export function UsageIndicator({ isOpen, onClose, projectId, anchorRect }: Usage
         </div>
 
         <div className="usage-content" ref={contentRef}>
-          {(loading || (!hasCompletedInitialFetchRef.current && !error)) && providers.length === 0 ? (
+          {(!hasFetched && !error) && providers.length === 0 ? (
             <UsageSkeleton />
           ) : error && providers.length === 0 ? (
             <div className="usage-error">

packages/dashboard/app/hooks/__tests__/useUsageData.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect, vi, beforeEach } from "vitest";
-import { renderHook, waitFor } from "@testing-library/react";
+import { act, renderHook, waitFor } from "@testing-library/react";
 import { useUsageData } from "../useUsageData";
 import * as api from "../../api";
 
@@ -7,7 +7,7 @@ describe("useUsageData", () => {
   const mockFetchUsageData = vi.spyOn(api, "fetchUsageData");
 
   beforeEach(() => {
-    mockFetchUsageData.mockClear();
+    mockFetchUsageData.mockReset();
   });
 
   it("fetches data on initial mount", async () => {
@@ -25,16 +25,16 @@ describe("useUsageData", () => {
 
     const { result } = renderHook(() => useUsageData({ autoRefresh: false }));
 
-    // Should be loading initially
     expect(result.current.loading).toBe(true);
     expect(result.current.providers).toEqual([]);
+    expect(result.current.hasFetched).toBe(false);
 
-    // Wait for data to load
     await waitFor(() => expect(result.current.loading).toBe(false));
 
     expect(result.current.providers).toEqual(mockData.providers);
     expect(result.current.error).toBeNull();
     expect(result.current.lastUpdated).toBeInstanceOf(Date);
+    expect(result.current.hasFetched).toBe(true);
   });
 
   it("handles fetch errors", async () => {
@@ -42,10 +42,13 @@ describe("useUsageData", () => {
 
     const { result } = renderHook(() => useUsageData({ autoRefresh: false }));
 
+    expect(result.current.hasFetched).toBe(false);
+
     await waitFor(() => expect(result.current.loading).toBe(false));
 
     expect(result.current.error).toBe("Network error");
     expect(result.current.providers).toEqual([]);
+    expect(result.current.hasFetched).toBe(true);
   });
 
   it("manual refresh fetches new data", async () => {
@@ -64,11 +67,14 @@ describe("useUsageData", () => {
 
     await waitFor(() => expect(result.current.loading).toBe(false));
     expect(result.current.providers).toEqual(mockData1.providers);
+    expect(result.current.hasFetched).toBe(true);
 
-    // Manual refresh
-    await result.current.refresh();
+    await act(async () => {
+      await result.current.refresh();
+    });
 
     await waitFor(() => expect(result.current.providers).toEqual(mockData2.providers));
+    expect(result.current.hasFetched).toBe(true);
   });
 
   it("clears error on successful manual refresh after error", async () => {
@@ -82,12 +88,29 @@ describe("useUsageData", () => {
 
     await waitFor(() => expect(result.current.loading).toBe(false));
     expect(result.current.error).toBe("Network error");
+    expect(result.current.hasFetched).toBe(true);
 
-    // Manual refresh
-    await result.current.refresh();
+    await act(async () => {
+      await result.current.refresh();
+    });
 
     await waitFor(() => expect(result.current.error).toBeNull());
     expect(result.current.providers).toHaveLength(1);
+    expect(result.current.hasFetched).toBe(true);
+  });
+
+  it("sets hasFetched to true after a successful empty fetch", async () => {
+    mockFetchUsageData.mockResolvedValue({ providers: [] });
+
+    const { result } = renderHook(() => useUsageData({ autoRefresh: false }));
+
+    expect(result.current.hasFetched).toBe(false);
+
+    await waitFor(() => expect(result.current.loading).toBe(false));
+
+    expect(result.current.providers).toEqual([]);
+    expect(result.current.error).toBeNull();
+    expect(result.current.hasFetched).toBe(true);
   });
 
   it("exports the correct interface", () => {
@@ -95,7 +118,7 @@ describe("useUsageData", () => {
   });
 
   it("returns expected default values before first fetch", () => {
-    mockFetchUsageData.mockImplementation(() => new Promise(() => {})); // Never resolves
+    mockFetchUsageData.mockImplementation(() => new Promise(() => {}));
 
     const { result } = renderHook(() => useUsageData({ autoRefresh: false }));
 
@@ -103,6 +126,7 @@ describe("useUsageData", () => {
     expect(result.current.loading).toBe(true);
     expect(result.current.error).toBeNull();
     expect(result.current.lastUpdated).toBeNull();
+    expect(result.current.hasFetched).toBe(false);
     expect(typeof result.current.refresh).toBe("function");
   });
 });

packages/dashboard/app/hooks/useUsageData.ts

@@ -7,6 +7,7 @@ interface UsageDataState {
   loading: boolean;
   error: string | null;
   lastUpdated: Date | null;
+  hasFetched: boolean;
 }
 
 interface UseUsageDataOptions {
@@ -34,6 +35,7 @@ export function useUsageData(options: UseUsageDataOptions = {}) {
     loading: true,
     error: null,
     lastUpdated: null,
+    hasFetched: false,
   });
 
   const pollRef = useRef<ReturnType<typeof setInterval> | null>(null);
@@ -57,6 +59,7 @@ export function useUsageData(options: UseUsageDataOptions = {}) {
         loading: false,
         error: null,
         lastUpdated: new Date(),
+        hasFetched: true,
       });
     } catch (err) {
       // Don't update state if the request was aborted
@@ -66,6 +69,7 @@ export function useUsageData(options: UseUsageDataOptions = {}) {
         ...prev,
         loading: false,
         error: getErrorMessage(err) || "Failed to fetch usage data",
+        hasFetched: true,
       }));
     }
   }, []);
@@ -112,6 +116,7 @@ export function useUsageData(options: UseUsageDataOptions = {}) {
     loading: state.loading,
     error: state.error,
     lastUpdated: state.lastUpdated,
+    hasFetched: state.hasFetched,
     refresh,
   };
 }