🔒 fix: Request interceptor for Shared Link Page Scenarios (#12036)

* ♻️ refactor: Centralize `buildLoginRedirectUrl` in data-provider

Move `buildLoginRedirectUrl` from `client/src/utils/redirect.ts` into
`packages/data-provider/src/api-endpoints.ts` so the axios 401
interceptor (and any other data-provider consumer) can use the canonical
implementation with the LOGIN_PATH_RE guard and BASE_URL awareness.

The client module now re-exports from `librechat-data-provider`, keeping
all existing imports working unchanged.

* 🔒 fix: Shared link 401 interceptor bypass and redirect loop (#12033)

Fixes three issues in the axios 401 response interceptor that prevented
private shared links (ALLOW_SHARED_LINKS_PUBLIC=false) from working:

1. `window.location.href.includes('share/')` matched the full URL
   (including query params and hash), causing false positives. Changed
   to `window.location.pathname.startsWith('/share/')`.

2. When token refresh returned no token on a share page, the
   interceptor logged and fell through without redirecting, causing an
   infinite retry loop via React Query. Now redirects to login using
   `buildLoginRedirectUrl()` which preserves the share URL for
   post-login navigation.

3. `processQueue` was never called in the no-token branch, leaving
   queued requests with dangling promise callbacks. Added
   `processQueue(error, null)` before the redirect.

* ✅ test: Comprehensive 401 interceptor tests for shared link auth flow

Rewrite interceptor test suite to cover all shared link auth scenarios:

- Unauthenticated user on share page with failed refresh → redirect
- Authenticated user on share page with failed refresh → redirect
- share/ in query params does NOT bypass the auth header guard
- Login path guard: redirect to plain /login (no redirect_to loop)
- Refresh success: assert exact call count (toBe(3) vs toBeGreaterThan)

Test reliability improvements:
- window.location teardown moved to afterEach (no state leak on failure)
- expect.assertions(N) on all tests (catch silent false passes)
- Shared setWindowLocation helper for consistent location mocking

* ♻️ refactor: Import `buildLoginRedirectUrl` directly from data-provider

Update `AuthContext.tsx` and `useAuthRedirect.ts` to import
`buildLoginRedirectUrl` from `librechat-data-provider` instead of
re-exporting through `~/utils/redirect.ts`.

Convert `redirect.ts` to ESM-style inline exports and remove the
re-export of `buildLoginRedirectUrl`.

* ✅ test: Move `buildLoginRedirectUrl` tests to data-provider

Tests for `buildLoginRedirectUrl` now live alongside the implementation
in `packages/data-provider/specs/api-endpoints.spec.ts`.

Removed the duplicate describe block from the client redirect test file
since it no longer owns that function.

packages/data-provider/specs/api-endpoints.spec.ts

@@ -0,0 +1,86 @@
+/**
+ * @jest-environment jsdom
+ */
+import { buildLoginRedirectUrl } from '../src/api-endpoints';
+
+describe('buildLoginRedirectUrl', () => {
+  let savedLocation: Location;
+
+  beforeEach(() => {
+    savedLocation = window.location;
+    Object.defineProperty(window, 'location', {
+      value: { pathname: '/c/abc123', search: '?model=gpt-4', hash: '#msg-5' },
+      writable: true,
+    });
+  });
+
+  afterEach(() => {
+    Object.defineProperty(window, 'location', { value: savedLocation, writable: true });
+  });
+
+  it('builds a login URL from explicit args', () => {
+    const result = buildLoginRedirectUrl('/c/new', '?q=hello', '');
+    expect(result).toBe('/login?redirect_to=%2Fc%2Fnew%3Fq%3Dhello');
+  });
+
+  it('encodes complex paths with query and hash', () => {
+    const result = buildLoginRedirectUrl('/c/new', '?q=hello&submit=true', '#section');
+    expect(result).toContain('redirect_to=');
+    const encoded = result.split('redirect_to=')[1];
+    expect(decodeURIComponent(encoded)).toBe('/c/new?q=hello&submit=true#section');
+  });
+
+  it('falls back to window.location when no args provided', () => {
+    const result = buildLoginRedirectUrl();
+    const encoded = result.split('redirect_to=')[1];
+    expect(decodeURIComponent(encoded)).toBe('/c/abc123?model=gpt-4#msg-5');
+  });
+
+  it('falls back to "/" when all location parts are empty', () => {
+    Object.defineProperty(window, 'location', {
+      value: { pathname: '', search: '', hash: '' },
+      writable: true,
+    });
+    const result = buildLoginRedirectUrl();
+    expect(result).toBe('/login?redirect_to=%2F');
+  });
+
+  it('returns plain /login when pathname is /login (prevents recursive redirect)', () => {
+    const result = buildLoginRedirectUrl('/login', '?redirect_to=%2Fc%2Fnew', '');
+    expect(result).toBe('/login');
+  });
+
+  it('returns plain /login when window.location is already /login', () => {
+    Object.defineProperty(window, 'location', {
+      value: { pathname: '/login', search: '?redirect_to=%2Fc%2Fabc', hash: '' },
+      writable: true,
+    });
+    const result = buildLoginRedirectUrl();
+    expect(result).toBe('/login');
+  });
+
+  it('returns plain /login for /login sub-paths', () => {
+    const result = buildLoginRedirectUrl('/login/2fa', '', '');
+    expect(result).toBe('/login');
+  });
+
+  it('returns plain /login for basename-prefixed /login (e.g. /librechat/login)', () => {
+    Object.defineProperty(window, 'location', {
+      value: { pathname: '/librechat/login', search: '?redirect_to=%2Fc%2Fabc', hash: '' },
+      writable: true,
+    });
+    const result = buildLoginRedirectUrl();
+    expect(result).toBe('/login');
+  });
+
+  it('returns plain /login for basename-prefixed /login sub-paths', () => {
+    const result = buildLoginRedirectUrl('/librechat/login/2fa', '', '');
+    expect(result).toBe('/login');
+  });
+
+  it('does NOT match paths where "login" is a substring of a segment', () => {
+    const result = buildLoginRedirectUrl('/c/loginhistory', '', '');
+    expect(result).toContain('redirect_to=');
+    expect(decodeURIComponent(result.split('redirect_to=')[1])).toBe('/c/loginhistory');
+  });
+});

packages/data-provider/specs/request-interceptor.spec.ts

@@ -13,20 +13,20 @@ import { setTokenHeader } from '../src/headers-helpers';
  * a refresh POST or is immediately rejected.
  */
 
-/** Mock the axios adapter to simulate responses without HTTP */
 const mockAdapter = jest.fn();
 let originalAdapter: typeof axios.defaults.adapter;
+let savedLocation: Location;
 
 beforeAll(async () => {
   originalAdapter = axios.defaults.adapter;
   axios.defaults.adapter = mockAdapter;
 
-  /** Import triggers interceptor registration */
   await import('../src/request');
 });
 
 beforeEach(() => {
   mockAdapter.mockReset();
+  savedLocation = window.location;
 });
 
 afterAll(() => {
@@ -35,14 +35,24 @@ afterAll(() => {
 
 afterEach(() => {
   delete axios.defaults.headers.common['Authorization'];
+  Object.defineProperty(window, 'location', {
+    value: savedLocation,
+    writable: true,
+  });
 });
 
+function setWindowLocation(overrides: Partial<Location>) {
+  Object.defineProperty(window, 'location', {
+    value: { ...window.location, ...overrides },
+    writable: true,
+  });
+}
+
 describe('axios 401 interceptor — Authorization header guard', () => {
   it('skips refresh and rejects when Authorization header is cleared', async () => {
-    /** Simulate a cleared header (as done by setTokenHeader(undefined) during logout) */
+    expect.assertions(1);
     setTokenHeader(undefined);
 
-    /** Set up adapter: first call returns 401, second would be the refresh */
     mockAdapter.mockRejectedValueOnce({
       response: { status: 401 },
       config: { url: '/api/messages', headers: {} },
@@ -54,23 +64,213 @@ describe('axios 401 interceptor — Authorization header guard', () => {
       // expected rejection
     }
 
-    /**
-     * If the interceptor skipped refresh, only 1 call was made (the original).
-     * If it attempted refresh, there would be 2+ calls (original + refresh POST).
-     */
     expect(mockAdapter).toHaveBeenCalledTimes(1);
   });
 
-  it('attempts refresh when Authorization header is present', async () => {
-    setTokenHeader('valid-token');
+  it('attempts refresh on shared link page even without Authorization header', async () => {
+    expect.assertions(2);
+    setTokenHeader(undefined);
+
+    setWindowLocation({
+      href: 'http://localhost/share/abc123',
+      pathname: '/share/abc123',
+      search: '',
+      hash: '',
+    } as Partial<Location>);
 
-    /** First call: 401 on the original request */
     mockAdapter.mockRejectedValueOnce({
       response: { status: 401 },
-      config: { url: '/api/messages', headers: {}, _retry: false },
+      config: { url: '/api/share/abc123', headers: {} },
+    });
+
+    mockAdapter.mockResolvedValueOnce({
+      data: { token: 'new-token' },
+      status: 200,
+      headers: {},
+      config: {},
+    });
+
+    mockAdapter.mockResolvedValueOnce({
+      data: { sharedLink: {} },
+      status: 200,
+      headers: {},
+      config: {},
+    });
+
+    try {
+      await axios.get('/api/share/abc123');
+    } catch {
+      // may reject depending on exact flow
+    }
+
+    expect(mockAdapter.mock.calls.length).toBe(3);
+
+    const refreshCall = mockAdapter.mock.calls[1];
+    expect(refreshCall[0].url).toContain('api/auth/refresh');
+  });
+
+  it('does not bypass guard when share/ appears only in query params', async () => {
+    expect.assertions(1);
+    setTokenHeader(undefined);
+
+    setWindowLocation({
+      href: 'http://localhost/c/chat?ref=share/token',
+      pathname: '/c/chat',
+      search: '?ref=share/token',
+      hash: '',
+    } as Partial<Location>);
+
+    mockAdapter.mockRejectedValueOnce({
+      response: { status: 401 },
+      config: { url: '/api/messages', headers: {} },
+    });
+
+    try {
+      await axios.get('/api/messages');
+    } catch {
+      // expected rejection
+    }
+
+    expect(mockAdapter).toHaveBeenCalledTimes(1);
+  });
+
+  it('redirects to login with redirect_to when unauthenticated on share page and refresh fails', async () => {
+    expect.assertions(1);
+    setTokenHeader(undefined);
+
+    setWindowLocation({
+      href: 'http://localhost/share/abc123',
+      pathname: '/share/abc123',
+      search: '',
+      hash: '',
+    } as Partial<Location>);
+
+    mockAdapter.mockRejectedValueOnce({
+      response: { status: 401 },
+      config: { url: '/api/share/abc123', headers: {} },
+    });
+
+    mockAdapter.mockResolvedValueOnce({
+      data: { token: '' },
+      status: 200,
+      headers: {},
+      config: {},
+    });
+
+    try {
+      await axios.get('/api/share/abc123');
+    } catch {
+      // expected rejection
+    }
+
+    expect(window.location.href).toBe('/login?redirect_to=%2Fshare%2Fabc123');
+  });
+
+  it('redirects to login with redirect_to when authenticated and refresh returns no token on share page', async () => {
+    expect.assertions(1);
+    setTokenHeader('some-token');
+
+    setWindowLocation({
+      href: 'http://localhost/share/abc123',
+      pathname: '/share/abc123',
+      search: '',
+      hash: '',
+    } as Partial<Location>);
+
+    mockAdapter.mockRejectedValueOnce({
+      response: { status: 401 },
+      config: { url: '/api/share/abc123', headers: {} },
+    });
+
+    mockAdapter.mockResolvedValueOnce({
+      data: { token: '' },
+      status: 200,
+      headers: {},
+      config: {},
+    });
+
+    try {
+      await axios.get('/api/share/abc123');
+    } catch {
+      // expected rejection
+    }
+
+    expect(window.location.href).toBe('/login?redirect_to=%2Fshare%2Fabc123');
+  });
+
+  it('redirects to login with redirect_to when refresh returns no token on regular page', async () => {
+    expect.assertions(1);
+    setTokenHeader('some-token');
+
+    setWindowLocation({
+      href: 'http://localhost/c/some-conversation',
+      pathname: '/c/some-conversation',
+      search: '',
+      hash: '',
+    } as Partial<Location>);
+
+    mockAdapter.mockRejectedValueOnce({
+      response: { status: 401 },
+      config: { url: '/api/messages', headers: {} },
+    });
+
+    mockAdapter.mockResolvedValueOnce({
+      data: { token: '' },
+      status: 200,
+      headers: {},
+      config: {},
+    });
+
+    try {
+      await axios.get('/api/messages');
+    } catch {
+      // expected rejection
+    }
+
+    expect(window.location.href).toBe('/login?redirect_to=%2Fc%2Fsome-conversation');
+  });
+
+  it('redirects to plain /login without redirect_to when already on a login path', async () => {
+    expect.assertions(1);
+    setTokenHeader('some-token');
+
+    setWindowLocation({
+      href: 'http://localhost/login/2fa',
+      pathname: '/login/2fa',
+      search: '',
+      hash: '',
+    } as Partial<Location>);
+
+    mockAdapter.mockRejectedValueOnce({
+      response: { status: 401 },
+      config: { url: '/api/messages', headers: {} },
+    });
+
+    mockAdapter.mockResolvedValueOnce({
+      data: { token: '' },
+      status: 200,
+      headers: {},
+      config: {},
+    });
+
+    try {
+      await axios.get('/api/messages');
+    } catch {
+      // expected rejection
+    }
+
+    expect(window.location.href).toBe('/login');
+  });
+
+  it('attempts refresh when Authorization header is present', async () => {
+    expect.assertions(2);
+    setTokenHeader('valid-token');
+
+    mockAdapter.mockRejectedValueOnce({
+      response: { status: 401 },
+      config: { url: '/api/messages', headers: {}, _retry: false },
     });
 
-    /** Second call: the refresh endpoint succeeds */
     mockAdapter.mockResolvedValueOnce({
       data: { token: 'new-token' },
       status: 200,
@@ -78,7 +278,6 @@ describe('axios 401 interceptor — Authorization header guard', () => {
       config: {},
     });
 
-    /** Third call: retried original request succeeds */
     mockAdapter.mockResolvedValueOnce({
       data: { messages: [] },
       status: 200,
@@ -92,10 +291,8 @@ describe('axios 401 interceptor — Authorization header guard', () => {
       // may reject depending on exact flow
     }
 
-    /** More than 1 call means the interceptor attempted refresh */
-    expect(mockAdapter.mock.calls.length).toBeGreaterThan(1);
+    expect(mockAdapter.mock.calls.length).toBe(3);
 
-    /** Verify the second call targeted the refresh endpoint */
     const refreshCall = mockAdapter.mock.calls[1];
     expect(refreshCall[0].url).toContain('api/auth/refresh');
   });