diff --git a/src/__tests__/OnboardingScreen.test.tsx b/src/__tests__/OnboardingScreen.test.tsx
index e8363fe..6a67ea9 100644
--- a/src/__tests__/OnboardingScreen.test.tsx
+++ b/src/__tests__/OnboardingScreen.test.tsx
@@ -304,6 +304,44 @@ describe('OnboardingScreen', () => {
     expect(authenticate).not.toHaveBeenCalled();
   });
 
+  it('does not authenticate when the wallet is disconnected but a public key exists', async () => {
+    walletStoreState = { isConnected: false, publicKey: 'GNOTCONNECTED' };
+
+    tree = await renderScreen();
+
+    expect(authenticate).not.toHaveBeenCalled();
+  });
+
+  it('does not re-authenticate an unchanged connected wallet on re-render', async () => {
+    walletStoreState = { isConnected: true, publicKey: 'GSAME' };
+
+    tree = await renderScreen();
+
+    expect(authenticate).toHaveBeenCalledWith('GSAME');
+
+    walletStoreState = { isConnected: true, publicKey: 'GSAME' };
+    await act(async () => {
+      tree!.update(<OnboardingScreen />);
+    });
+
+    expect(authenticate).toHaveBeenCalledTimes(1);
+  });
+
+  it('authenticates again when the connected public key changes', async () => {
+    walletStoreState = { isConnected: true, publicKey: 'GOLD' };
+
+    tree = await renderScreen();
+
+    expect(authenticate).toHaveBeenCalledWith('GOLD');
+
+    walletStoreState = { isConnected: true, publicKey: 'GNEW' };
+    await act(async () => {
+      tree!.update(<OnboardingScreen />);
+    });
+
+    expect(authenticate).toHaveBeenCalledWith('GNEW');
+  });
+
   it('displays wallet connection errors', async () => {
     walletHookState.error = 'Freighter extension not detected';
 
diff --git a/src/__tests__/useAuth.test.ts b/src/__tests__/useAuth.test.ts
new file mode 100644
index 0000000..f81bc1a
--- /dev/null
+++ b/src/__tests__/useAuth.test.ts
@@ -0,0 +1,138 @@
+import { renderHook, act } from '@testing-library/react';
+import useAuth from '../hooks/useAuth';
+import * as api from '../api';
+import * as stellar from '../stellar';
+import * as lobstr from '../lobstr';
+import * as walletVault from '../walletVault';
+import { useWalletStore } from '../stores/walletStore';
+import { useUserStore } from '../stores/userStore';
+
+jest.mock('../api');
+jest.mock('../stellar');
+jest.mock('../lobstr');
+jest.mock('../walletVault');
+jest.mock('../stores/walletStore');
+jest.mock('../stores/userStore');
+
+let w = {}, u = {};
+const wh = useWalletStore as any, uh = useUserStore as any;
+
+beforeEach(() => {
+  jest.clearAllMocks();
+  w = { address: 'G1', walletType: 'freighter' };
+  u = { token: null, profile: null };
+  wh.mockImplementation((sel?: any) => sel ? sel(w) : w);
+  wh.getState = () => w;
+  wh.setState = (up: any) => w = typeof up === 'function' ? up(w) : { ...w, ...up };
+  uh.mockImplementation((sel?: any) => sel ? sel(u) : u);
+  uh.getState = () => u;
+  uh.setState = (up: any) => u = typeof up === 'function' ? up(u) : { ...u, ...up };
+  (api.getAuthChallenge as jest.Mock).mockResolved('ch');
+  (api.loginWithWallet as jest.Mock).mockResolved('jwt');
+  (api.fetchUserProfile as jest.Mock).mockResolved({});
+  (stellar.signChallengeXDR as jest.Mock).mockResolved('sig');
+  (lobstr.openLobstrForSigning as jest.Mock).mockResolved('lob');
+  (walletVault.getInAppSecret as jest.Mock).mockResolved('sec');
+});
+const render = () => renderHook(() => useAuth());
+const login = async (r: any) => act(async () => { await r.current.login(); });
+
+describe('useAuth', () => {
+  it('lobstr', async () => {
+    w.walletType = 'lobstr'; w.address = 'GLOB';
+    const r = render(); await login(r);
+    expect(lobstr.openLobstrForSigning).toHaveBeenCalledWith('ch');
+    expect(api.loginWithWallet).toHaveBeenCalledWith('lob');
+  });
+
+  it('freighter', async () => {
+    w.walletType = 'freighter'; w.address = 'GFRE';
+    const r = render(); await login(r);
+    expect(stellar.signChallengeXDR).toHaveBeenCalledWith('ch', { address: 'GFRE', walletType: 'freighter' });
+  });
+
+  it('keypair', async () => {
+    w.walletType = 'keypair'; w.address = 'GKEY';
+    const r = render(); await login(r);
+    expect(walletVault.getInAppSecret).toHaveBeenCalled();
+    expect(stellar.signChallengeXDR).toHaveBeenCalledWith('ch', { secretKey: 'sec' });
+  });
+
+  it('missing secret', async () => {
+    w.walletType = 'keypair'; w.address = 'GKEY';
+    (walletVault.getInAppSecret as jest.Mock).mockResolved(null);
+    const r = render();
+    await expect(r.current.login()).rejects.toThrow();
+  });
+
+  it('network error on challenge', async () => {
+    (api.getAuthChallenge as jest.Mock).mockRejected(new Error('network'));
+    const r = render();
+    await expect(r.current.login()).rejects.toThrow('network');
+  });
+
+  it('network error on login', async () => {
+    w.walletType = 'freighter'; w.address = 'GFRE';
+    (api.loginWithWallet as jest.Mock).mockRejected(new Error('network'));
+    const r = render();
+    await expect(r.current.login()).rejects.toThrow('network');
+  });
+
+  it('signing error', async () => {
+    w.walletType = 'freighter'; w.address = 'GFRE';
+    (stellar.signChallengeXDR as jest.Mock).mockRejected(new Error('signing'));
+    const r = render();
+    await expect(r.current.login()).rejects.toThrow('signing');
+  });
+
+  it('stores JWT and profile', async () => {
+    w.walletType = 'freighter'; w.address = 'GFRE';
+    (api.fetchUserProfile as jest.Mock).mockResolved({ id: 'u1', stats: { games: 1 } });
+    const r = render(); await login(r);
+    expect(u.token).toBe('jwt');
+    expect(u.profile).toEqual({ id: 'u1', stats: { games: 1 } });
+  });
+
+  it('does not set profile on fetch error', async () => {
+    w.walletType = 'freighter'; w.address = 'GFRE';
+    (api.fetchUserProfile as jest.Mock).mockRejected(new Error('profile'));
+    const r = render(); await login(r);
+    expect(u.profile).toBe(null);
+  });
+
+  it('preserves stats on partial profile', async () => {
+    w.walletType = 'freighter'; w.address = 'GFRE';
+    u.profile = { id: 'u1', stats: { games: 10, wins: 5 } };
+    (api.fetchUserProfile as jest.Mock).mockResolved({ id: 'u1', stats: { games: 10 } });
+    const r = render(); await login(r);
+    expect(u.profile.stats).toEqual({ games: 10, wins: 5 });
+  });
+
+  it('syncProfile fetches profile', async () => {
+    u.token = 'token';
+    (api.fetchUserProfile as jest.Mock).mockResolved({ id: 'x', stats: { games: 2 } });
+    const r = render(); await act(async () => { await r.current.syncProfile(); });
+    expect(api.fetchUserProfile).toHaveBeenCalledWith('token');
+    expect(u.profile).toEqual({ id: 'x', stats: { games: 2 } });
+  });
+
+  it('syncProfile preserves stats on partial data', async () => {
+    u.token = 'token';
+    u.profile = { id: 'x', stats: { games: 10, wins: 3 } };
+    (api.fetchUserProfile as jest.Mock).mockResolved({ id: 'x', stats: { games: 10 } });
+    const r = render(); await act(async () => { await r.current.syncProfile(); });
+    expect(u.profile.stats).toEqual({ games: 10, wins: 3 });
+  });
+
+  it('syncProfile does nothing without token', async () => {
+    const r = render(); await act(async () => { await r.current.syncProfile(); });
+    expect(api.fetchUserProfile).not.toHaveBeenCalled();
+  });
+
+  it('syncProfile rejects on fetch error', async () => {
+    u.token = 'token';
+    (api.fetchUserProfile as jest.Mock).mockRejected(new Error('profile'));
+    const r = render();
+    await expect(r.current.syncProfile()).rejects.toThrow('profile');
+  });
+});
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