diff --git a/src/store/authStore.login.test.ts b/src/store/authStore.login.test.ts
new file mode 100644
index 00000000..7eb4a948
--- /dev/null
+++ b/src/store/authStore.login.test.ts
@@ -0,0 +1,139 @@
+/**
+ * Login / session / connection-state characterization for `authStore`.
+ *
+ * authStore has no single `login()` action — the UI composes:
+ *   pingWithCredentials → addServer → setActiveServer → setLoggedIn
+ * Tests target that composed sequence + the connection-state surface
+ * (`isConnecting`, `connectionError`) and the Last.fm session helpers.
+ *
+ * Phase F2 / PR 3 of the pre-refactor testing plan.
+ */
+import { beforeEach, describe, expect, it } from 'vitest';
+import { useAuthStore } from './authStore';
+import { resetAuthStore } from '@/test/helpers/storeReset';
+import { makeServer } from '@/test/helpers/factories';
+
+beforeEach(() => {
+  resetAuthStore();
+});
+
+describe('login flow (composed)', () => {
+  it('successful login: addServer → setActiveServer → setLoggedIn pins the active session', () => {
+    const profile = makeServer({ name: 'Home' });
+    const { addServer, setActiveServer, setLoggedIn } = useAuthStore.getState();
+
+    const id = addServer({ name: profile.name, url: profile.url, username: profile.username, password: profile.password });
+    setActiveServer(id);
+    setLoggedIn(true);
+
+    const s = useAuthStore.getState();
+    expect(s.servers).toHaveLength(1);
+    expect(s.servers[0]?.id).toBe(id);
+    expect(s.servers[0]?.name).toBe('Home');
+    expect(s.activeServerId).toBe(id);
+    expect(s.isLoggedIn).toBe(true);
+  });
+
+  it('failed login (no addServer call) leaves prior valid state intact', () => {
+    const existing = makeServer({ name: 'Existing' });
+    const existingId = useAuthStore.getState().addServer({
+      name: existing.name, url: existing.url, username: existing.username, password: existing.password,
+    });
+    useAuthStore.getState().setActiveServer(existingId);
+    useAuthStore.getState().setLoggedIn(true);
+
+    // Simulate ping failure — the UI sets connecting + error but does NOT
+    // touch servers / activeServerId / isLoggedIn.
+    useAuthStore.getState().setConnecting(true);
+    useAuthStore.getState().setConnectionError('connection refused');
+    useAuthStore.getState().setConnecting(false);
+
+    const s = useAuthStore.getState();
+    expect(s.servers).toHaveLength(1);
+    expect(s.servers[0]?.id).toBe(existingId);
+    expect(s.activeServerId).toBe(existingId);
+    expect(s.isLoggedIn).toBe(true);
+    expect(s.connectionError).toBe('connection refused');
+  });
+
+  it('addServer assigns a unique id even for duplicate-payload calls', () => {
+    const make = () => useAuthStore.getState().addServer({
+      name: 'Same', url: 'https://same.test', username: 'u', password: 'p',
+    });
+    const id1 = make();
+    const id2 = make();
+    expect(id1).not.toBe(id2);
+    expect(useAuthStore.getState().servers).toHaveLength(2);
+  });
+});
+
+describe('connection state', () => {
+  it('setConnecting / setConnectionError toggle the loading + error fields independently', () => {
+    const { setConnecting, setConnectionError } = useAuthStore.getState();
+
+    setConnecting(true);
+    expect(useAuthStore.getState().isConnecting).toBe(true);
+
+    setConnectionError('boom');
+    expect(useAuthStore.getState().connectionError).toBe('boom');
+
+    setConnecting(false);
+    setConnectionError(null);
+    expect(useAuthStore.getState().isConnecting).toBe(false);
+    expect(useAuthStore.getState().connectionError).toBeNull();
+  });
+});
+
+describe('logout', () => {
+  it('clears isLoggedIn + musicFolders but keeps the server entry', () => {
+    const id = useAuthStore.getState().addServer({
+      name: 'Home', url: 'https://x.test', username: 'u', password: 'p',
+    });
+    useAuthStore.getState().setActiveServer(id);
+    useAuthStore.getState().setLoggedIn(true);
+    useAuthStore.getState().setMusicFolders([{ id: 'mf-1', name: 'Music' }]);
+
+    useAuthStore.getState().logout();
+
+    const s = useAuthStore.getState();
+    expect(s.isLoggedIn).toBe(false);
+    expect(s.musicFolders).toEqual([]);
+    expect(s.servers).toHaveLength(1);
+    expect(s.activeServerId).toBe(id);
+  });
+});
+
+describe('Last.fm session', () => {
+  it('setLastfm stores api key + secret + session key + username together', () => {
+    useAuthStore.getState().setLastfm('api', 'sec', 'session', 'frank');
+    const s = useAuthStore.getState();
+    expect(s.lastfmApiKey).toBe('api');
+    expect(s.lastfmApiSecret).toBe('sec');
+    expect(s.lastfmSessionKey).toBe('session');
+    expect(s.lastfmUsername).toBe('frank');
+  });
+
+  it('connectLastfm sets only sessionKey + username (preserves api key / secret)', () => {
+    useAuthStore.getState().setLastfm('app-key', 'app-sec', '', '');
+    useAuthStore.getState().connectLastfm('user-session', 'frank');
+    const s = useAuthStore.getState();
+    expect(s.lastfmApiKey).toBe('app-key');
+    expect(s.lastfmApiSecret).toBe('app-sec');
+    expect(s.lastfmSessionKey).toBe('user-session');
+    expect(s.lastfmUsername).toBe('frank');
+  });
+
+  it('disconnectLastfm clears session key + username + session error, keeps app credentials', () => {
+    useAuthStore.getState().setLastfm('app-key', 'app-sec', 'session', 'frank');
+    useAuthStore.getState().setLastfmSessionError(true);
+
+    useAuthStore.getState().disconnectLastfm();
+
+    const s = useAuthStore.getState();
+    expect(s.lastfmSessionKey).toBe('');
+    expect(s.lastfmUsername).toBe('');
+    expect(s.lastfmSessionError).toBe(false);
+    expect(s.lastfmApiKey).toBe('app-key');
+    expect(s.lastfmApiSecret).toBe('app-sec');
+  });
+});
diff --git a/src/store/authStore.persistence.test.ts b/src/store/authStore.persistence.test.ts
new file mode 100644
index 00000000..040fdc0c
--- /dev/null
+++ b/src/store/authStore.persistence.test.ts
@@ -0,0 +1,202 @@
+/**
+ * authStore persistence + sync-storage characterization.
+ *
+ * Covers Zustand persist's hydration path (via `useAuthStore.persist.rehydrate()`):
+ * existing localStorage shapes load, missing fields default to the store's
+ * initial values, corrupt JSON does not crash bootstrap, the
+ * hotCacheEnabled / preloadMode≠'off' conflicting-legacy migration clears
+ * both, and a few smaller field-level migrations.
+ *
+ * Also pins the **synchronous storage** invariant called out in `CLAUDE.md`
+ * ("never switch to async storage") — regression §2 of the pre-refactor
+ * testing plan v2.
+ *
+ * Phase F2 / PR 3.
+ */
+import { beforeEach, describe, expect, it } from 'vitest';
+import { useAuthStore } from './authStore';
+import { resetAuthStore } from '@/test/helpers/storeReset';
+
+const PERSIST_KEY = 'psysonic-auth';
+
+function writePersistedState(state: Record<string, unknown>): void {
+  localStorage.setItem(PERSIST_KEY, JSON.stringify({ state, version: 0 }));
+}
+
+beforeEach(() => {
+  resetAuthStore();
+  localStorage.removeItem(PERSIST_KEY);
+});
+
+describe('hydration — loads existing localStorage shape', () => {
+  it('restores servers + activeServerId from a fresh-shape payload', async () => {
+    const server = { id: 's1', name: 'Home', url: 'https://x.test', username: 'u', password: 'p' };
+    writePersistedState({ servers: [server], activeServerId: 's1' });
+
+    await useAuthStore.persist.rehydrate();
+
+    const s = useAuthStore.getState();
+    expect(s.servers).toHaveLength(1);
+    expect(s.servers[0]?.id).toBe('s1');
+    expect(s.activeServerId).toBe('s1');
+  });
+
+  it('defaults missing fields to their initial values', async () => {
+    // Minimal payload — no scrobblingEnabled, no replayGain settings, etc.
+    writePersistedState({ servers: [], activeServerId: null });
+
+    await useAuthStore.persist.rehydrate();
+
+    const s = useAuthStore.getState();
+    expect(s.scrobblingEnabled).toBe(true);
+    expect(s.crossfadeEnabled).toBe(false);
+    expect(s.gaplessEnabled).toBe(false);
+    expect(s.replayGainEnabled).toBe(false);
+    expect(s.normalizationEngine).toBe('off');
+    expect(s.preloadMode).toBe('balanced');
+  });
+
+  it('preserves saved fields verbatim when present', async () => {
+    writePersistedState({
+      servers: [],
+      activeServerId: null,
+      scrobblingEnabled: false,
+      crossfadeEnabled: true,
+      gaplessEnabled: false,
+      crossfadeSecs: 7,
+    });
+
+    await useAuthStore.persist.rehydrate();
+
+    const s = useAuthStore.getState();
+    expect(s.scrobblingEnabled).toBe(false);
+    expect(s.crossfadeEnabled).toBe(true);
+    expect(s.crossfadeSecs).toBe(7);
+  });
+});
+
+describe('hydration — corrupt / unexpected input', () => {
+  it('does not crash bootstrap when the persisted blob is not valid JSON', async () => {
+    localStorage.setItem(PERSIST_KEY, '{not[json}');
+    await expect(useAuthStore.persist.rehydrate()).resolves.not.toThrow();
+
+    const s = useAuthStore.getState();
+    // No servers loaded; defaults remain.
+    expect(s.servers).toEqual([]);
+    expect(s.scrobblingEnabled).toBe(true);
+  });
+
+  it('is robust to a missing top-level `state` field', async () => {
+    localStorage.setItem(PERSIST_KEY, JSON.stringify({ version: 0 }));
+    await expect(useAuthStore.persist.rehydrate()).resolves.not.toThrow();
+    expect(useAuthStore.getState().servers).toEqual([]);
+  });
+});
+
+describe('onRehydrate migrations', () => {
+  it('clears the conflicting hotCacheEnabled + preloadMode≠"off" legacy combo', async () => {
+    writePersistedState({
+      servers: [],
+      activeServerId: null,
+      hotCacheEnabled: true,
+      preloadMode: 'balanced',
+    });
+
+    await useAuthStore.persist.rehydrate();
+
+    const s = useAuthStore.getState();
+    expect(s.hotCacheEnabled).toBe(false);
+    expect(s.preloadMode).toBe('off');
+  });
+
+  it('keeps hotCacheEnabled when preloadMode was already "off"', async () => {
+    writePersistedState({
+      servers: [],
+      activeServerId: null,
+      hotCacheEnabled: true,
+      preloadMode: 'off',
+    });
+
+    await useAuthStore.persist.rehydrate();
+
+    const s = useAuthStore.getState();
+    expect(s.hotCacheEnabled).toBe(true);
+    expect(s.preloadMode).toBe('off');
+  });
+
+  it('migrates a legacy `waveform` seekbarStyle to `truewave`', async () => {
+    writePersistedState({
+      servers: [],
+      activeServerId: null,
+      seekbarStyle: 'waveform', // legacy / no longer in VALID_SEEKBAR_STYLES
+    });
+
+    await useAuthStore.persist.rehydrate();
+    expect(useAuthStore.getState().seekbarStyle).toBe('truewave');
+  });
+
+  it('keeps a valid seekbarStyle unchanged', async () => {
+    writePersistedState({
+      servers: [],
+      activeServerId: null,
+      seekbarStyle: 'neon',
+    });
+
+    await useAuthStore.persist.rehydrate();
+    expect(useAuthStore.getState().seekbarStyle).toBe('neon');
+  });
+
+  it('strips the removed `animationMode` and `reducedAnimations` legacy fields', async () => {
+    writePersistedState({
+      servers: [],
+      activeServerId: null,
+      animationMode: 'reduced',
+      reducedAnimations: true,
+    });
+
+    await useAuthStore.persist.rehydrate();
+    const s = useAuthStore.getState() as unknown as Record<string, unknown>;
+    expect(s.animationMode).toBeUndefined();
+    expect(s.reducedAnimations).toBeUndefined();
+  });
+});
+
+describe('partialize — what gets persisted', () => {
+  it('strips `musicFolders` from the persisted payload', () => {
+    useAuthStore.setState({ musicFolders: [{ id: 'mf-1', name: 'Music' }] });
+    // Trigger persist (Zustand persist writes on every state change).
+    useAuthStore.setState({ scrobblingEnabled: false });
+
+    const raw = localStorage.getItem(PERSIST_KEY);
+    expect(raw).not.toBeNull();
+    const parsed = JSON.parse(raw!) as { state: Record<string, unknown> };
+    expect(parsed.state.musicFolders).toBeUndefined();
+  });
+});
+
+describe('synchronous storage invariant (CLAUDE.md gotcha)', () => {
+  // Regression §2 of the v2 eval doc: a refactor that swaps localStorage
+  // for an async store (e.g. @tauri-apps/plugin-store) would break the
+  // bootstrap path — `getActiveServer()` would return undefined for one
+  // event-loop tick after `addServer` + `setActiveServer`.
+  it('addServer + setActiveServer → getActiveServer is visible in the same tick (no await)', () => {
+    const id = useAuthStore.getState().addServer({
+      name: 'Sync', url: 'https://sync.test', username: 'u', password: 'p',
+    });
+    useAuthStore.getState().setActiveServer(id);
+
+    // No `await` between the writes and the read. If storage were async
+    // the activeServerId would not yet be reflected by `getActiveServer`.
+    expect(useAuthStore.getState().getActiveServer()?.id).toBe(id);
+    expect(useAuthStore.getState().getActiveServer()?.name).toBe('Sync');
+  });
+
+  it('exposes a synchronous getter API — never returns a Promise', () => {
+    // Type-level + runtime check that the selectors stay sync.
+    const active = useAuthStore.getState().getActiveServer();
+    const baseUrl = useAuthStore.getState().getBaseUrl();
+    expect(active).not.toBeInstanceOf(Promise);
+    expect(baseUrl).not.toBeInstanceOf(Promise);
+    expect(typeof baseUrl).toBe('string');
+  });
+});
diff --git a/src/store/authStore.servers.test.ts b/src/store/authStore.servers.test.ts
new file mode 100644
index 00000000..889d4499
--- /dev/null
+++ b/src/store/authStore.servers.test.ts
@@ -0,0 +1,184 @@
+/**
+ * Server add / remove / update / switch characterization for `authStore`.
+ *
+ * Also includes the gapless / crossfade mutual-exclusion regression test
+ * from §4.3 of the pre-refactor testing plan v2 — both flags live on
+ * `authStore`, both UI surfaces (Settings + QueuePanel toolbar) clear the
+ * other one before setting their own. A refactor that pushes mutex
+ * enforcement into the setters would change the contract; the tests pin
+ * the current caller-clears-first behaviour.
+ *
+ * Phase F2 / PR 3.
+ */
+import { beforeEach, describe, expect, it } from 'vitest';
+import { useAuthStore } from './authStore';
+import { resetAuthStore } from '@/test/helpers/storeReset';
+import { makeServer } from '@/test/helpers/factories';
+
+function addThree(): { a: string; b: string; c: string } {
+  const a = useAuthStore.getState().addServer({ name: 'A', url: 'https://a.test', username: 'u', password: 'p' });
+  const b = useAuthStore.getState().addServer({ name: 'B', url: 'https://b.test', username: 'u', password: 'p' });
+  const c = useAuthStore.getState().addServer({ name: 'C', url: 'https://c.test', username: 'u', password: 'p' });
+  return { a, b, c };
+}
+
+beforeEach(() => {
+  resetAuthStore();
+});
+
+describe('addServer / updateServer', () => {
+  it('appends a new server and returns its id', () => {
+    const id = useAuthStore.getState().addServer({
+      name: 'Home', url: 'https://x.test', username: 'u', password: 'p',
+    });
+    const s = useAuthStore.getState();
+    expect(s.servers).toHaveLength(1);
+    expect(s.servers[0]?.id).toBe(id);
+    expect(s.servers[0]?.name).toBe('Home');
+  });
+
+  it('updateServer patches the matching server only', () => {
+    const { a, b } = addThree();
+    useAuthStore.getState().updateServer(a, { name: 'A-renamed', url: 'https://a-new.test' });
+    const s = useAuthStore.getState();
+    const sa = s.servers.find(srv => srv.id === a);
+    const sb = s.servers.find(srv => srv.id === b);
+    expect(sa?.name).toBe('A-renamed');
+    expect(sa?.url).toBe('https://a-new.test');
+    expect(sb?.name).toBe('B');
+    expect(sb?.url).toBe('https://b.test');
+  });
+
+  it('updateServer is a no-op for an unknown id', () => {
+    const { a } = addThree();
+    const before = useAuthStore.getState().servers;
+    useAuthStore.getState().updateServer('unknown-id', { name: 'X' });
+    expect(useAuthStore.getState().servers).toEqual(before);
+    expect(useAuthStore.getState().servers.find(s => s.id === a)?.name).toBe('A');
+  });
+});
+
+describe('setActiveServer', () => {
+  it('updates activeServerId and clears musicFolders (forces a refetch)', () => {
+    const { a, b } = addThree();
+    useAuthStore.getState().setActiveServer(a);
+    useAuthStore.getState().setMusicFolders([{ id: 'mf-1', name: 'Music' }]);
+
+    useAuthStore.getState().setActiveServer(b);
+    const s = useAuthStore.getState();
+    expect(s.activeServerId).toBe(b);
+    expect(s.musicFolders).toEqual([]);
+  });
+});
+
+describe('removeServer', () => {
+  it('removes a non-active server without touching activeServerId or isLoggedIn', () => {
+    const { a, b } = addThree();
+    useAuthStore.getState().setActiveServer(a);
+    useAuthStore.getState().setLoggedIn(true);
+
+    useAuthStore.getState().removeServer(b);
+    const s = useAuthStore.getState();
+    expect(s.servers.map(srv => srv.id)).not.toContain(b);
+    expect(s.activeServerId).toBe(a);
+    expect(s.isLoggedIn).toBe(true);
+  });
+
+  it('removing the active server picks newServers[0] as the deterministic fallback', () => {
+    const { a, b, c } = addThree();
+    useAuthStore.getState().setActiveServer(a);
+
+    useAuthStore.getState().removeServer(a);
+    const s = useAuthStore.getState();
+    expect(s.servers.map(srv => srv.id)).toEqual([b, c]);
+    expect(s.activeServerId).toBe(b);
+  });
+
+  it('removing the only / active server clears activeServerId to null and forces logout', () => {
+    const id = useAuthStore.getState().addServer({ name: 'Solo', url: 'https://s.test', username: 'u', password: 'p' });
+    useAuthStore.getState().setActiveServer(id);
+    useAuthStore.getState().setLoggedIn(true);
+
+    useAuthStore.getState().removeServer(id);
+    const s = useAuthStore.getState();
+    expect(s.servers).toHaveLength(0);
+    expect(s.activeServerId).toBeNull();
+    expect(s.isLoggedIn).toBe(false);
+  });
+
+  it('cleans associated per-server bookkeeping maps (entityRatingSupport / instantMix / …)', () => {
+    const { a, b } = addThree();
+    useAuthStore.setState({
+      entityRatingSupportByServer: { [a]: 'full', [b]: 'track_only' },
+    });
+
+    useAuthStore.getState().removeServer(a);
+    expect(useAuthStore.getState().entityRatingSupportByServer).toEqual({ [b]: 'track_only' });
+  });
+
+  it('does not touch activeServerId when the removed id was inactive', () => {
+    const { a, b } = addThree();
+    useAuthStore.getState().setActiveServer(b);
+    useAuthStore.getState().removeServer(a);
+    expect(useAuthStore.getState().activeServerId).toBe(b);
+  });
+});
+
+describe('selectors — getBaseUrl / getActiveServer', () => {
+  it('getActiveServer returns the entry matching activeServerId', () => {
+    const { a, b } = addThree();
+    useAuthStore.getState().setActiveServer(b);
+    expect(useAuthStore.getState().getActiveServer()?.id).toBe(b);
+  });
+
+  it('getActiveServer returns undefined when no server is active', () => {
+    expect(useAuthStore.getState().getActiveServer()).toBeUndefined();
+  });
+
+  it('getBaseUrl strips trailing slashes and adds http:// when missing', () => {
+    useAuthStore.getState().addServer({ name: 'A', url: 'http://a.test/', username: 'u', password: 'p' });
+    const a = useAuthStore.getState().servers[0]!.id;
+    useAuthStore.getState().setActiveServer(a);
+    expect(useAuthStore.getState().getBaseUrl()).toBe('http://a.test');
+
+    const b = useAuthStore.getState().addServer({ name: 'B', url: 'b.local', username: 'u', password: 'p' });
+    useAuthStore.getState().setActiveServer(b);
+    expect(useAuthStore.getState().getBaseUrl()).toBe('http://b.local');
+  });
+
+  it('getBaseUrl returns empty string when no server is active', () => {
+    expect(useAuthStore.getState().getBaseUrl()).toBe('');
+  });
+});
+
+describe('audio modes — gapless / crossfade mutual exclusion (regression §4.3 of v2 plan)', () => {
+  it('enabling gapless after the caller clears crossfade yields gapless-only', () => {
+    useAuthStore.setState({ crossfadeEnabled: true, gaplessEnabled: false });
+    // Caller pattern matches Settings.tsx:2565 — gapless toggle clears crossfade first.
+    useAuthStore.getState().setCrossfadeEnabled(false);
+    useAuthStore.getState().setGaplessEnabled(true);
+    const s = useAuthStore.getState();
+    expect(s.crossfadeEnabled).toBe(false);
+    expect(s.gaplessEnabled).toBe(true);
+  });
+
+  it('enabling crossfade after the caller clears gapless yields crossfade-only', () => {
+    useAuthStore.setState({ crossfadeEnabled: false, gaplessEnabled: true });
+    useAuthStore.getState().setGaplessEnabled(false);
+    useAuthStore.getState().setCrossfadeEnabled(true);
+    const s = useAuthStore.getState();
+    expect(s.gaplessEnabled).toBe(false);
+    expect(s.crossfadeEnabled).toBe(true);
+  });
+
+  it('the setters themselves do NOT auto-clear the other flag — callers are responsible', () => {
+    // Pinning the current contract: a refactor that moves mutex enforcement
+    // into the setters would silently change behaviour for any caller that
+    // doesn't already clear first.
+    useAuthStore.setState({ crossfadeEnabled: true, gaplessEnabled: false });
+    useAuthStore.getState().setGaplessEnabled(true);
+    // Both end up true because the setter is a pure assignment.
+    expect(useAuthStore.getState().crossfadeEnabled).toBe(true);
+    expect(useAuthStore.getState().gaplessEnabled).toBe(true);
+  });
+});
diff --git a/src/store/authStore.settings.test.ts b/src/store/authStore.settings.test.ts
new file mode 100644
index 00000000..b9e790e2
--- /dev/null
+++ b/src/store/authStore.settings.test.ts
@@ -0,0 +1,314 @@
+/**
+ * Setter-surface characterization for `authStore`.
+ *
+ * Pins the setter API so a refactor that renames or removes one of the
+ * dozens of `setX: (v) => set({ x: v })` action methods fails loudly.
+ * Most setters are trivial; the ones with logic (clamping, validation,
+ * transforms, side effects) get a focused test for the non-trivial bit.
+ *
+ * Phase F2 / PR 3.
+ */
+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),
+  setRating: vi.fn(async () => undefined),
+}));
+
+import { useAuthStore } from './authStore';
+import { resetAuthStore, resetPlayerStore } from '@/test/helpers/storeReset';
+import { onInvoke } from '@/test/mocks/tauri';
+
+beforeEach(() => {
+  resetAuthStore();
+  resetPlayerStore();
+  onInvoke('audio_update_replay_gain', () => undefined);
+  onInvoke('audio_set_normalization', () => undefined);
+});
+
+describe('trivial pass-through setters', () => {
+  // Quick API-pin sweep. Each setter is `setX: (v) => set({ x: v })` —
+  // a refactor that renames a key without renaming the setter (or vice
+  // versa) breaks these.
+  it.each([
+    ['setScrobblingEnabled', 'scrobblingEnabled', false],
+    ['setExcludeAudiobooks', 'excludeAudiobooks', true],
+    ['setInfiniteQueueEnabled', 'infiniteQueueEnabled', true],
+    ['setPreservePlayNextOrder', 'preservePlayNextOrder', true],
+    ['setShowArtistImages', 'showArtistImages', true],
+    ['setShowTrayIcon', 'showTrayIcon', false],
+    ['setMinimizeToTray', 'minimizeToTray', true],
+    ['setShowOrbitTrigger', 'showOrbitTrigger', false],
+    ['setDiscordRichPresence', 'discordRichPresence', true],
+    ['setEnableBandsintown', 'enableBandsintown', true],
+    ['setUseCustomTitlebar', 'useCustomTitlebar', true],
+    ['setPreloadMiniPlayer', 'preloadMiniPlayer', true],
+    ['setLinuxWebkitKineticScroll', 'linuxWebkitKineticScroll', false],
+    ['setNowPlayingEnabled', 'nowPlayingEnabled', true],
+    ['setShowFullscreenLyrics', 'showFullscreenLyrics', false],
+    ['setLyricsStaticOnly', 'lyricsStaticOnly', true],
+    ['setShowChangelogOnUpdate', 'showChangelogOnUpdate', false],
+    ['setQueueNowPlayingCollapsed', 'queueNowPlayingCollapsed', true],
+    ['setEnableHiRes', 'enableHiRes', true],
+    ['setHotCacheEnabled', 'hotCacheEnabled', true],
+    ['setMixMinRatingFilterEnabled', 'mixMinRatingFilterEnabled', true],
+    ['setShowLuckyMixMenu', 'showLuckyMixMenu', false],
+  ])('%s writes to %s', (setter, key, value) => {
+    const setFn = (useAuthStore.getState() as unknown as Record<string, unknown>)[setter];
+    expect(typeof setFn).toBe('function');
+    (setFn as (v: unknown) => void)(value);
+    expect((useAuthStore.getState() as unknown as Record<string, unknown>)[key]).toBe(value);
+  });
+
+  it.each([
+    ['setMaxCacheMb', 'maxCacheMb', 2048],
+    ['setHotCacheMaxMb', 'hotCacheMaxMb', 1024],
+    ['setHotCacheDebounceSec', 'hotCacheDebounceSec', 60],
+    ['setPreloadCustomSeconds', 'preloadCustomSeconds', 45],
+    ['setFsPortraitDim', 'fsPortraitDim', 64],
+  ])('%s stores a numeric value', (setter, key, value) => {
+    (useAuthStore.getState() as unknown as Record<string, (v: unknown) => void>)[setter](value);
+    expect((useAuthStore.getState() as unknown as Record<string, unknown>)[key]).toBe(value);
+  });
+
+  it.each([
+    ['setDownloadFolder', 'downloadFolder', '/tmp/downloads'],
+    ['setOfflineDownloadDir', 'offlineDownloadDir', '/tmp/offline'],
+    ['setHotCacheDownloadDir', 'hotCacheDownloadDir', '/tmp/hot'],
+    ['setLastSeenChangelogVersion', 'lastSeenChangelogVersion', '1.46.0'],
+    ['setDiscordTemplateDetails', 'discordTemplateDetails', '{artist} — {title}'],
+    ['setDiscordTemplateState', 'discordTemplateState', '{album}'],
+    ['setDiscordTemplateLargeText', 'discordTemplateLargeText', 'Hi'],
+  ])('%s stores a string value', (setter, key, value) => {
+    (useAuthStore.getState() as unknown as Record<string, (v: unknown) => void>)[setter](value);
+    expect((useAuthStore.getState() as unknown as Record<string, unknown>)[key]).toBe(value);
+  });
+});
+
+describe('setters with validation / clamping', () => {
+  it('setTrackPreviewStartRatio clamps to [0, 0.9]', () => {
+    useAuthStore.getState().setTrackPreviewStartRatio(1.5);
+    expect(useAuthStore.getState().trackPreviewStartRatio).toBe(0.9);
+
+    useAuthStore.getState().setTrackPreviewStartRatio(-0.5);
+    expect(useAuthStore.getState().trackPreviewStartRatio).toBe(0);
+
+    useAuthStore.getState().setTrackPreviewStartRatio(0.33);
+    expect(useAuthStore.getState().trackPreviewStartRatio).toBe(0.33);
+  });
+
+  it('setTrackPreviewDurationSec clamps to [5, 120] and rounds to whole seconds', () => {
+    useAuthStore.getState().setTrackPreviewDurationSec(300);
+    expect(useAuthStore.getState().trackPreviewDurationSec).toBe(120);
+
+    useAuthStore.getState().setTrackPreviewDurationSec(2);
+    expect(useAuthStore.getState().trackPreviewDurationSec).toBe(5);
+
+    useAuthStore.getState().setTrackPreviewDurationSec(30.7);
+    expect(useAuthStore.getState().trackPreviewDurationSec).toBe(31);
+  });
+
+  it('setTrackPreviewsEnabled coerces truthy/falsy to boolean', () => {
+    useAuthStore.getState().setTrackPreviewsEnabled('yes' as unknown as boolean);
+    expect(useAuthStore.getState().trackPreviewsEnabled).toBe(true);
+
+    useAuthStore.getState().setTrackPreviewsEnabled(0 as unknown as boolean);
+    expect(useAuthStore.getState().trackPreviewsEnabled).toBe(false);
+  });
+
+  it('setTrackPreviewLocation toggles a single location entry by key', () => {
+    const before = useAuthStore.getState().trackPreviewLocations;
+    const firstKey = Object.keys(before)[0] as keyof typeof before;
+    useAuthStore.getState().setTrackPreviewLocation(firstKey, !before[firstKey]);
+    expect(useAuthStore.getState().trackPreviewLocations[firstKey]).toBe(!before[firstKey]);
+  });
+
+  it('setLoudnessPreAnalysisAttenuationDb rejects non-finite input', () => {
+    const before = useAuthStore.getState().loudnessPreAnalysisAttenuationDb;
+    useAuthStore.getState().setLoudnessPreAnalysisAttenuationDb(Number.NaN);
+    expect(useAuthStore.getState().loudnessPreAnalysisAttenuationDb).toBe(before);
+
+    useAuthStore.getState().setLoudnessPreAnalysisAttenuationDb(Number.POSITIVE_INFINITY);
+    expect(useAuthStore.getState().loudnessPreAnalysisAttenuationDb).toBe(before);
+  });
+
+  it('resetLoudnessPreAnalysisAttenuationDbDefault restores the canonical default', () => {
+    useAuthStore.getState().setLoudnessPreAnalysisAttenuationDb(-2);
+    useAuthStore.getState().resetLoudnessPreAnalysisAttenuationDbDefault();
+    expect(useAuthStore.getState().loudnessPreAnalysisAttenuationDb).toBe(-4.5);
+  });
+});
+
+describe('replay-gain related setters (write through to player store)', () => {
+  it('setReplayGainEnabled writes the flag (and pings updateReplayGainForCurrentTrack)', () => {
+    useAuthStore.getState().setReplayGainEnabled(true);
+    expect(useAuthStore.getState().replayGainEnabled).toBe(true);
+    useAuthStore.getState().setReplayGainEnabled(false);
+    expect(useAuthStore.getState().replayGainEnabled).toBe(false);
+  });
+
+  it('setNormalizationEngine accepts off / replaygain / loudness', () => {
+    useAuthStore.getState().setNormalizationEngine('replaygain');
+    expect(useAuthStore.getState().normalizationEngine).toBe('replaygain');
+    useAuthStore.getState().setNormalizationEngine('loudness');
+    expect(useAuthStore.getState().normalizationEngine).toBe('loudness');
+    useAuthStore.getState().setNormalizationEngine('off');
+    expect(useAuthStore.getState().normalizationEngine).toBe('off');
+  });
+
+  it('setReplayGainMode supports track / album / auto', () => {
+    useAuthStore.getState().setReplayGainMode('track');
+    expect(useAuthStore.getState().replayGainMode).toBe('track');
+    useAuthStore.getState().setReplayGainMode('album');
+    expect(useAuthStore.getState().replayGainMode).toBe('album');
+    useAuthStore.getState().setReplayGainMode('auto');
+    expect(useAuthStore.getState().replayGainMode).toBe('auto');
+  });
+
+  it('setReplayGainPreGainDb / setReplayGainFallbackDb store dB values', () => {
+    useAuthStore.getState().setReplayGainPreGainDb(-3);
+    useAuthStore.getState().setReplayGainFallbackDb(-7);
+    expect(useAuthStore.getState().replayGainPreGainDb).toBe(-3);
+    expect(useAuthStore.getState().replayGainFallbackDb).toBe(-7);
+  });
+
+  it('setLoudnessTargetLufs stores the target', () => {
+    useAuthStore.getState().setLoudnessTargetLufs(-14);
+    expect(useAuthStore.getState().loudnessTargetLufs).toBe(-14);
+  });
+});
+
+describe('preload mode + discord cover source setters', () => {
+  it('setPreloadMode accepts off / balanced / early / custom', () => {
+    for (const mode of ['off', 'balanced', 'early', 'custom'] as const) {
+      useAuthStore.getState().setPreloadMode(mode);
+      expect(useAuthStore.getState().preloadMode).toBe(mode);
+    }
+  });
+
+  it('setDiscordCoverSource accepts none / apple / server', () => {
+    for (const src of ['none', 'apple', 'server'] as const) {
+      useAuthStore.getState().setDiscordCoverSource(src);
+      expect(useAuthStore.getState().discordCoverSource).toBe(src);
+    }
+  });
+
+  it('setLoggingMode accepts off / normal / debug', () => {
+    for (const mode of ['off', 'normal', 'debug'] as const) {
+      useAuthStore.getState().setLoggingMode(mode);
+      expect(useAuthStore.getState().loggingMode).toBe(mode);
+    }
+  });
+});
+
+describe('per-server bookkeeping setters', () => {
+  it('setEntityRatingSupport scopes the value to the given serverId', () => {
+    useAuthStore.getState().setEntityRatingSupport('srv-1', 'full');
+    useAuthStore.getState().setEntityRatingSupport('srv-2', 'track_only');
+    expect(useAuthStore.getState().entityRatingSupportByServer).toEqual({
+      'srv-1': 'full',
+      'srv-2': 'track_only',
+    });
+  });
+
+  it('setAudiomuseNavidromeEnabled adds positive opt-ins and removes disabled entries', () => {
+    useAuthStore.getState().setAudiomuseNavidromeEnabled('srv-1', true);
+    useAuthStore.getState().setAudiomuseNavidromeEnabled('srv-2', true);
+    expect(useAuthStore.getState().audiomuseNavidromeByServer).toEqual({
+      'srv-1': true,
+      'srv-2': true,
+    });
+
+    // Disabling removes the entry rather than storing `false` — the map
+    // tracks positive opt-ins only.
+    useAuthStore.getState().setAudiomuseNavidromeEnabled('srv-1', false);
+    expect(useAuthStore.getState().audiomuseNavidromeByServer).toEqual({
+      'srv-2': true,
+    });
+  });
+
+  it('setAudiomuseNavidromeIssue scopes by serverId', () => {
+    useAuthStore.getState().setAudiomuseNavidromeIssue('srv-1', true);
+    expect(useAuthStore.getState().audiomuseNavidromeIssueByServer).toEqual({
+      'srv-1': true,
+    });
+  });
+});
+
+describe('genre blacklist + audio output device', () => {
+  it('setCustomGenreBlacklist replaces the list', () => {
+    useAuthStore.getState().setCustomGenreBlacklist(['Audiobook', 'Podcast']);
+    expect(useAuthStore.getState().customGenreBlacklist).toEqual(['Audiobook', 'Podcast']);
+
+    useAuthStore.getState().setCustomGenreBlacklist([]);
+    expect(useAuthStore.getState().customGenreBlacklist).toEqual([]);
+  });
+
+  it('setAudioOutputDevice stores the device id or null', () => {
+    useAuthStore.getState().setAudioOutputDevice('hw:0,0');
+    expect(useAuthStore.getState().audioOutputDevice).toBe('hw:0,0');
+
+    useAuthStore.getState().setAudioOutputDevice(null);
+    expect(useAuthStore.getState().audioOutputDevice).toBeNull();
+  });
+});
+
+describe('lyrics source setters', () => {
+  it('setLyricsSources replaces the source list verbatim', () => {
+    const sources = [
+      { id: 'lrclib' as const, enabled: true },
+      { id: 'server' as const, enabled: false },
+      { id: 'netease' as const, enabled: true },
+    ];
+    useAuthStore.getState().setLyricsSources(sources);
+    expect(useAuthStore.getState().lyricsSources).toEqual(sources);
+  });
+
+  it('setLyricsMode + setFsLyricsStyle + setSidebarLyricsStyle write enum values through', () => {
+    useAuthStore.getState().setLyricsMode('lyricsplus');
+    expect(useAuthStore.getState().lyricsMode).toBe('lyricsplus');
+
+    useAuthStore.getState().setFsLyricsStyle('apple');
+    expect(useAuthStore.getState().fsLyricsStyle).toBe('apple');
+
+    useAuthStore.getState().setSidebarLyricsStyle('apple');
+    expect(useAuthStore.getState().sidebarLyricsStyle).toBe('apple');
+  });
+});
+
+describe('mix filter setters — clamp to allowed range', () => {
+  it('setMixMinRatingSong / Album / Artist clamp out-of-range stars', () => {
+    useAuthStore.getState().setMixMinRatingSong(10);
+    useAuthStore.getState().setMixMinRatingAlbum(-3);
+    useAuthStore.getState().setMixMinRatingArtist(0);
+    const s = useAuthStore.getState();
+    // The clamp function bounds to 0–5; values outside that range get pulled in.
+    expect(s.mixMinRatingSong).toBeGreaterThanOrEqual(0);
+    expect(s.mixMinRatingSong).toBeLessThanOrEqual(5);
+    expect(s.mixMinRatingAlbum).toBeGreaterThanOrEqual(0);
+    expect(s.mixMinRatingAlbum).toBeLessThanOrEqual(5);
+    expect(s.mixMinRatingArtist).toBeGreaterThanOrEqual(0);
+    expect(s.mixMinRatingArtist).toBeLessThanOrEqual(5);
+  });
+
+  it('setRandomMixSize clamps to a sensible range', () => {
+    useAuthStore.getState().setRandomMixSize(10_000);
+    const huge = useAuthStore.getState().randomMixSize;
+    expect(huge).toBeLessThan(10_000);
+
+    useAuthStore.getState().setRandomMixSize(-5);
+    expect(useAuthStore.getState().randomMixSize).toBeGreaterThanOrEqual(0);
+  });
+});