diff --git a/src/components/FullscreenPlayer.test.tsx b/src/components/FullscreenPlayer.test.tsx
new file mode 100644
index 00000000..3dd5b0fe
--- /dev/null
+++ b/src/components/FullscreenPlayer.test.tsx
@@ -0,0 +1,186 @@
+/**
+ * `FullscreenPlayer` characterization (Phase F5c).
+ *
+ * Includes the §4.5 regression test from the v2 plan — the cover image
+ * must call `useCachedUrl(coverUrl, coverKey, false)`. The `false`
+ * third argument selects the fallback path that avoids a double
+ * crossfade (fetchUrl → blobUrl). A refactor that "tidies up" the
+ * useCachedUrl call sites would silently regress the FS player.
+ */
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+vi.mock('@/api/subsonic', () => ({
+  savePlayQueue: vi.fn(async () => undefined),
+  getPlayQueue: vi.fn(async () => ({ songs: [], current: undefined, position: 0 })),
+  buildStreamUrl: vi.fn((id: string) => `https://mock/stream/${id}`),
+  buildCoverArtUrl: vi.fn((id: string) => `https://mock/cover/${id}`),
+  buildDownloadUrl: vi.fn((id: string) => `https://mock/download/${id}`),
+  coverArtCacheKey: vi.fn((id: string, size = 256) => `mock:cover:${id}:${size}`),
+  getSong: vi.fn(async () => null),
+  getRandomSongs: vi.fn(async () => []),
+  getSimilarSongs2: vi.fn(async () => []),
+  getTopSongs: vi.fn(async () => []),
+  getAlbumInfo2: vi.fn(async () => null),
+  reportNowPlaying: vi.fn(async () => undefined),
+  scrobbleSong: vi.fn(async () => undefined),
+  star: vi.fn(async () => undefined),
+  unstar: vi.fn(async () => undefined),
+  getLyricsBySongId: vi.fn(async () => null),
+}));
+
+vi.mock('@/api/lastfm', () => ({
+  lastfmScrobble: vi.fn(async () => undefined),
+  lastfmUpdateNowPlaying: vi.fn(async () => undefined),
+  lastfmLoveTrack: vi.fn(async () => undefined),
+  lastfmUnloveTrack: vi.fn(async () => undefined),
+  lastfmGetTrackLoved: vi.fn(async () => false),
+  lastfmGetAllLovedTracks: vi.fn(async () => []),
+}));
+
+// `useCachedUrl` is the surface §4.5 needs to characterize. Mock the module
+// so we can assert the third positional arg `false` is preserved.
+vi.mock('./CachedImage', async () => {
+  const actual = await vi.importActual<typeof import('./CachedImage')>('./CachedImage');
+  return {
+    ...actual,
+    useCachedUrl: vi.fn((url, _key, opt) => `mock://${url}?opt=${String(opt ?? 'default')}`),
+  };
+});
+
+import FullscreenPlayer from './FullscreenPlayer';
+import { useCachedUrl } from './CachedImage';
+import { renderWithProviders } from '@/test/helpers/renderWithProviders';
+import { usePlayerStore } from '@/store/playerStore';
+import { useAuthStore } from '@/store/authStore';
+import { resetAllStores } from '@/test/helpers/storeReset';
+import { makeTrack } from '@/test/helpers/factories';
+import { onInvoke } from '@/test/mocks/tauri';
+import { fireEvent } from '@testing-library/react';
+
+beforeEach(() => {
+  resetAllStores();
+  const id = useAuthStore.getState().addServer({
+    name: 'T', url: 'https://x.test', username: 'u', password: 'p',
+  });
+  useAuthStore.getState().setActiveServer(id);
+  vi.mocked(useCachedUrl).mockClear();
+  onInvoke('audio_play', () => undefined);
+  onInvoke('audio_pause', () => undefined);
+  onInvoke('audio_stop', () => undefined);
+  onInvoke('audio_seek', () => undefined);
+  onInvoke('audio_get_state', () => ({ playing: false }));
+  onInvoke('audio_update_replay_gain', () => undefined);
+  onInvoke('discord_update_presence', () => undefined);
+});
+
+afterEach(() => {
+  vi.mocked(useCachedUrl).mockClear();
+});
+
+describe('FullscreenPlayer — render', () => {
+  it('renders the labelled Fullscreen Player dialog', () => {
+    usePlayerStore.setState({ currentTrack: makeTrack({ coverArt: 'art-1' }) });
+    const { getByLabelText } = renderWithProviders(
+      <FullscreenPlayer onClose={() => {}} />,
+    );
+    expect(getByLabelText('Fullscreen Player')).toBeInTheDocument();
+  });
+
+  it('exposes the Close Fullscreen button', () => {
+    usePlayerStore.setState({ currentTrack: makeTrack() });
+    const { getByLabelText } = renderWithProviders(
+      <FullscreenPlayer onClose={() => {}} />,
+    );
+    expect(getByLabelText('Close Fullscreen')).toBeInTheDocument();
+  });
+});
+
+describe('FullscreenPlayer — regression §4.5 of v2 plan', () => {
+  // The component calls `useCachedUrl` twice:
+  //   - line 338: for the small art box (default behaviour, opt=true)
+  //   - line 674: for the cover (opt=false, no fetchUrl fallback)
+  // The `false` arg is load-bearing — it avoids a double crossfade by
+  // routing through the cache-only path. Pin it.
+  it('passes opt=false on the cover-art useCachedUrl call (no fetchUrl fallback)', () => {
+    usePlayerStore.setState({ currentTrack: makeTrack({ coverArt: 'art-1' }) });
+    renderWithProviders(<FullscreenPlayer onClose={() => {}} />);
+
+    const calls = vi.mocked(useCachedUrl).mock.calls;
+    // Find the call whose cacheKey targets the 500 px cover (`...:cover:art-1:500`).
+    const coverCall = calls.find(c => typeof c[1] === 'string' && c[1].includes(':500'));
+    expect(coverCall).toBeDefined();
+    expect(coverCall?.[2]).toBe(false);
+  });
+
+  it('also issues a useCachedUrl call with the default behaviour for the small art box', () => {
+    usePlayerStore.setState({ currentTrack: makeTrack({ coverArt: 'art-1' }) });
+    renderWithProviders(<FullscreenPlayer onClose={() => {}} />);
+
+    const calls = vi.mocked(useCachedUrl).mock.calls;
+    // The 300 px art box uses the default (truthy) opt.
+    const artBoxCall = calls.find(c => typeof c[1] === 'string' && c[1].includes(':300'));
+    expect(artBoxCall).toBeDefined();
+    expect(artBoxCall?.[2]).toBe(true);
+  });
+});
+
+describe('FullscreenPlayer — control wiring', () => {
+  it('clicking Close Fullscreen calls the onClose prop', () => {
+    usePlayerStore.setState({ currentTrack: makeTrack() });
+    const onClose = vi.fn();
+    const { getByLabelText } = renderWithProviders(
+      <FullscreenPlayer onClose={onClose} />,
+    );
+    fireEvent.click(getByLabelText('Close Fullscreen'));
+    expect(onClose).toHaveBeenCalledTimes(1);
+  });
+
+  it('clicking Stop calls stop()', () => {
+    usePlayerStore.setState({ currentTrack: makeTrack() });
+    const stopSpy = vi.spyOn(usePlayerStore.getState(), 'stop');
+    const { getByLabelText } = renderWithProviders(
+      <FullscreenPlayer onClose={() => {}} />,
+    );
+    fireEvent.click(getByLabelText('Stop'));
+    expect(stopSpy).toHaveBeenCalledTimes(1);
+  });
+
+  it('clicking Previous Track calls previous()', () => {
+    usePlayerStore.setState({
+      queue: [makeTrack({ id: 'a' }), makeTrack({ id: 'b' })],
+      queueIndex: 1,
+      currentTrack: makeTrack({ id: 'b' }),
+      currentTime: 5,
+    });
+    const prevSpy = vi.spyOn(usePlayerStore.getState(), 'previous');
+    const { getByLabelText } = renderWithProviders(
+      <FullscreenPlayer onClose={() => {}} />,
+    );
+    fireEvent.click(getByLabelText('Previous Track'));
+    expect(prevSpy).toHaveBeenCalledTimes(1);
+  });
+
+  it('clicking Next Track calls next()', () => {
+    usePlayerStore.setState({
+      queue: [makeTrack({ id: 'a' }), makeTrack({ id: 'b' })],
+      queueIndex: 0,
+      currentTrack: makeTrack({ id: 'a' }),
+    });
+    const nextSpy = vi.spyOn(usePlayerStore.getState(), 'next');
+    const { getByLabelText } = renderWithProviders(
+      <FullscreenPlayer onClose={() => {}} />,
+    );
+    fireEvent.click(getByLabelText('Next Track'));
+    expect(nextSpy).toHaveBeenCalledTimes(1);
+  });
+
+  it('clicking Repeat cycles via toggleRepeat', () => {
+    usePlayerStore.setState({ currentTrack: makeTrack() });
+    const { getByLabelText } = renderWithProviders(
+      <FullscreenPlayer onClose={() => {}} />,
+    );
+    expect(usePlayerStore.getState().repeatMode).toBe('off');
+    fireEvent.click(getByLabelText('Repeat'));
+    expect(usePlayerStore.getState().repeatMode).toBe('all');
+  });
+});
diff --git a/src/components/MiniPlayer.test.tsx b/src/components/MiniPlayer.test.tsx
new file mode 100644
index 00000000..1295a152
--- /dev/null
+++ b/src/components/MiniPlayer.test.tsx
@@ -0,0 +1,91 @@
+/**
+ * `MiniPlayer` characterization (Phase F5c).
+ *
+ * Per pick 4a of the v2 plan: renders + click handlers only. The
+ * cross-webview bridge contract (`mini:ready` / `mini:sync` emit-listen,
+ * geometry persistence) is covered separately in B-tier phase B5; jsdom
+ * does not model two webviews, so an in-process test would only fake
+ * what we're trying to verify.
+ */
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+vi.mock('@/api/subsonic', () => ({
+  savePlayQueue: vi.fn(async () => undefined),
+  getPlayQueue: vi.fn(async () => ({ songs: [], current: undefined, position: 0 })),
+  buildStreamUrl: vi.fn((id: string) => `https://mock/stream/${id}`),
+  buildCoverArtUrl: vi.fn((id: string) => `https://mock/cover/${id}`),
+  buildDownloadUrl: vi.fn((id: string) => `https://mock/download/${id}`),
+  coverArtCacheKey: vi.fn((id: string, size = 256) => `mock:cover:${id}:${size}`),
+  getSong: vi.fn(async () => null),
+  getRandomSongs: vi.fn(async () => []),
+  getSimilarSongs2: vi.fn(async () => []),
+  getTopSongs: vi.fn(async () => []),
+  getAlbumInfo2: vi.fn(async () => null),
+  reportNowPlaying: vi.fn(async () => undefined),
+  scrobbleSong: vi.fn(async () => undefined),
+}));
+
+vi.mock('@/api/lastfm', () => ({
+  lastfmScrobble: vi.fn(async () => undefined),
+  lastfmUpdateNowPlaying: vi.fn(async () => undefined),
+  lastfmGetTrackLoved: vi.fn(async () => false),
+  lastfmGetAllLovedTracks: vi.fn(async () => []),
+}));
+
+import MiniPlayer from './MiniPlayer';
+import { renderWithProviders } from '@/test/helpers/renderWithProviders';
+import { useAuthStore } from '@/store/authStore';
+import { resetAllStores } from '@/test/helpers/storeReset';
+import { onInvoke } from '@/test/mocks/tauri';
+import { fireEvent } from '@testing-library/react';
+
+beforeEach(() => {
+  resetAllStores();
+  const id = useAuthStore.getState().addServer({
+    name: 'T', url: 'https://x.test', username: 'u', password: 'p',
+  });
+  useAuthStore.getState().setActiveServer(id);
+  onInvoke('audio_play', () => undefined);
+  onInvoke('audio_pause', () => undefined);
+  onInvoke('audio_seek', () => undefined);
+  onInvoke('audio_stop', () => undefined);
+  onInvoke('audio_get_state', () => ({ playing: false }));
+  onInvoke('set_window_always_on_top', () => undefined);
+  onInvoke('set_linux_webkit_smooth_scrolling', () => undefined);
+  onInvoke('discord_update_presence', () => undefined);
+});
+
+describe('MiniPlayer — render', () => {
+  it('mounts without throwing', () => {
+    expect(() => renderWithProviders(<MiniPlayer />)).not.toThrow();
+  });
+
+  it('renders the always-present titlebar controls (Pin + Open main window)', () => {
+    // The Close button is Linux-only — gated on `navigator.platform` and
+    // therefore not asserted here so the test passes on every jsdom env.
+    const { getByLabelText } = renderWithProviders(<MiniPlayer />);
+    expect(getByLabelText('Unpin')).toBeInTheDocument(); // initial state: alwaysOnTop=true
+    expect(getByLabelText('Open main window')).toBeInTheDocument();
+  });
+});
+
+describe('MiniPlayer — click handlers (no bridge)', () => {
+  it('clicking Open main window does not throw (bridge emit is a no-op in tests)', () => {
+    const { getByLabelText } = renderWithProviders(<MiniPlayer />);
+    expect(() => fireEvent.click(getByLabelText('Open main window'))).not.toThrow();
+  });
+
+  // The Close affordance is Linux-only — covered by manual smoke per pick 4a.
+
+  it('clicking the Pin button toggles the alwaysOnTop label', () => {
+    const { getByLabelText, queryByLabelText } = renderWithProviders(<MiniPlayer />);
+    // Initial state: alwaysOnTop=true → label is "Unpin".
+    expect(getByLabelText('Unpin')).toBeInTheDocument();
+
+    fireEvent.click(getByLabelText('Unpin'));
+
+    // Bridge command is mocked away; the local React state still flips,
+    // so the label moves to "Pin on top".
+    expect(queryByLabelText('Pin on top')).toBeInTheDocument();
+  });
+});
diff --git a/src/test/setup.ts b/src/test/setup.ts
index d7aacade..fd6df53d 100644
--- a/src/test/setup.ts
+++ b/src/test/setup.ts
@@ -89,8 +89,11 @@ vi.mock('@tauri-apps/api/core', () => ({
 
 vi.mock('@tauri-apps/api/event', () => ({
   listen: vi.fn(),
-  emit: vi.fn(),
-  once: vi.fn(),
+  // Components chain `.catch()` on emit; return a resolved Promise so the
+  // chain doesn't throw "Cannot read properties of undefined (reading
+  // 'catch')" inside a useEffect on first render.
+  emit: vi.fn(async () => undefined),
+  once: vi.fn(async () => () => {}),
 }));
 
 // Linker for Tauri shell / dialog / store plugins — same idea. Extend as needed.