diff --git a/api/server/middleware/__tests__/requireJwtAuth.spec.js b/api/server/middleware/__tests__/requireJwtAuth.spec.js
index a884cb5b3f..317e8ae6b4 100644
--- a/api/server/middleware/__tests__/requireJwtAuth.spec.js
+++ b/api/server/middleware/__tests__/requireJwtAuth.spec.js
@@ -8,7 +8,7 @@
  * If the chaining is removed, these tests fail.
  */
 
-const { getTenantId } = require('@librechat/data-schemas');
+const jwt = require('jsonwebtoken');
 
 // ── Mocks ──────────────────────────────────────────────────────────────
 
@@ -36,6 +36,15 @@ jest.mock('passport', () => ({
   }),
 }));
 
+jest.mock('@librechat/data-schemas', () => {
+  const { AsyncLocalStorage } = require('async_hooks');
+  const tenantStorage = new AsyncLocalStorage();
+  return {
+    getTenantId: () => tenantStorage.getStore()?.tenantId,
+    tenantStorage,
+  };
+});
+
 // Mock @librechat/api — the real tenantContextMiddleware is TS and cannot be
 // required directly from CJS tests. This thin wrapper mirrors the real logic
 // (read req.user.tenantId, call tenantStorage.run) using the same data-schemas
@@ -57,13 +66,20 @@ jest.mock('@librechat/api', () => {
 // ── Helpers ─────────────────────────────────────────────────────────────
 
 const requireJwtAuth = require('../requireJwtAuth');
+const { getTenantId } = require('@librechat/data-schemas');
 const { isEnabled } = require('@librechat/api');
 const passport = require('passport');
 
+const jwtSecret = 'test-refresh-secret';
+
 function mockReq(user, extra = {}) {
   return { headers: {}, _mockUser: user, ...extra };
 }
 
+function signedOpenIdUserCookie(userId = 'user-openid') {
+  return jwt.sign({ id: userId }, jwtSecret);
+}
+
 function mockRes() {
   return { status: jest.fn().mockReturnThis(), json: jest.fn().mockReturnThis() };
 }
@@ -82,12 +98,23 @@ function runAuth(user) {
 // ── Tests ──────────────────────────────────────────────────────────────
 
 describe('requireJwtAuth tenant context chaining', () => {
+  const originalJwtSecret = process.env.JWT_REFRESH_SECRET;
+
+  beforeEach(() => {
+    process.env.JWT_REFRESH_SECRET = jwtSecret;
+  });
+
   afterEach(() => {
     mockPassportError = null;
     mockRegisteredStrategies = new Set(['jwt']);
     isEnabled.mockReturnValue(false);
     passport.authenticate.mockClear();
     passport._strategy.mockClear();
+    if (originalJwtSecret === undefined) {
+      delete process.env.JWT_REFRESH_SECRET;
+    } else {
+      process.env.JWT_REFRESH_SECRET = originalJwtSecret;
+    }
   });
 
   it('forwards passport errors to next() without entering tenant middleware', async () => {
@@ -124,7 +151,7 @@ describe('requireJwtAuth tenant context chaining', () => {
     expect(getTenantId()).toBeUndefined();
   });
 
-  it('falls back to OpenID JWT for bearer-only reuse requests', async () => {
+  it('does not fall back to OpenID JWT for bearer-only reuse requests', () => {
     isEnabled.mockReturnValue(true);
     mockRegisteredStrategies.add('openidJwt');
     const req = mockReq(undefined, {
@@ -134,6 +161,32 @@ describe('requireJwtAuth tenant context chaining', () => {
       },
     });
     const res = mockRes();
+    const next = jest.fn();
+
+    requireJwtAuth(req, res, next);
+
+    expect(next).not.toHaveBeenCalled();
+    expect(res.status).toHaveBeenCalledWith(401);
+    expect(req.authStrategy).toBeUndefined();
+    expect(passport.authenticate).toHaveBeenCalledTimes(1);
+    expect(passport.authenticate).toHaveBeenCalledWith(
+      'jwt',
+      { session: false },
+      expect.any(Function),
+    );
+  });
+
+  it('uses OpenID JWT before LibreChat JWT when the OpenID cookie is present', async () => {
+    isEnabled.mockReturnValue(true);
+    mockRegisteredStrategies.add('openidJwt');
+    const req = mockReq(undefined, {
+      headers: { cookie: `token_provider=openid; openid_user_id=${signedOpenIdUserCookie()}` },
+      _mockStrategies: {
+        openidJwt: { user: { id: 'user-openid', tenantId: 'tenant-openid', role: 'user' } },
+        jwt: { user: false, info: { message: 'invalid signature' }, status: 401 },
+      },
+    });
+    const res = mockRes();
     const tenantId = await new Promise((resolve) => {
       requireJwtAuth(req, res, () => {
         resolve(getTenantId());
@@ -143,6 +196,98 @@ describe('requireJwtAuth tenant context chaining', () => {
     expect(tenantId).toBe('tenant-openid');
     expect(req.authStrategy).toBe('openidJwt');
     expect(res.status).not.toHaveBeenCalled();
+    expect(passport.authenticate).toHaveBeenCalledWith(
+      'openidJwt',
+      { session: false },
+      expect.any(Function),
+    );
+  });
+
+  it('does not authenticate OpenID JWT when the reuse cookie belongs to another user', () => {
+    isEnabled.mockReturnValue(true);
+    mockRegisteredStrategies.add('openidJwt');
+    const req = mockReq(undefined, {
+      headers: {
+        cookie: `token_provider=openid; openid_user_id=${signedOpenIdUserCookie('user-a')}`,
+      },
+      _mockStrategies: {
+        openidJwt: { user: { id: 'user-b', tenantId: 'tenant-openid', role: 'user' } },
+        jwt: { user: false, info: { message: 'invalid signature' }, status: 401 },
+      },
+    });
+    const res = mockRes();
+    const next = jest.fn();
+
+    requireJwtAuth(req, res, next);
+
+    expect(next).not.toHaveBeenCalled();
+    expect(res.status).toHaveBeenCalledWith(401);
+    expect(req.authStrategy).toBeUndefined();
+    expect(passport.authenticate).toHaveBeenCalledTimes(2);
+    expect(passport.authenticate).toHaveBeenNthCalledWith(
+      1,
+      'openidJwt',
+      { session: false },
+      expect.any(Function),
+    );
+    expect(passport.authenticate).toHaveBeenNthCalledWith(
+      2,
+      'jwt',
+      { session: false },
+      expect.any(Function),
+    );
+  });
+
+  it('does not use OpenID JWT when the signed OpenID reuse cookie is missing', () => {
+    isEnabled.mockReturnValue(true);
+    mockRegisteredStrategies.add('openidJwt');
+    const req = mockReq(undefined, {
+      headers: { cookie: 'token_provider=openid' },
+      _mockStrategies: {
+        jwt: { user: false, info: { message: 'invalid signature' }, status: 401 },
+        openidJwt: { user: { tenantId: 'tenant-openid', role: 'user' } },
+      },
+    });
+    const res = mockRes();
+    const next = jest.fn();
+
+    requireJwtAuth(req, res, next);
+
+    expect(next).not.toHaveBeenCalled();
+    expect(res.status).toHaveBeenCalledWith(401);
+    expect(req.authStrategy).toBeUndefined();
+    expect(passport.authenticate).toHaveBeenCalledTimes(1);
+    expect(passport.authenticate).toHaveBeenCalledWith(
+      'jwt',
+      { session: false },
+      expect.any(Function),
+    );
+  });
+
+  it('does not use OpenID JWT when the OpenID reuse cookie is invalid', () => {
+    isEnabled.mockReturnValue(true);
+    mockRegisteredStrategies.add('openidJwt');
+    const req = mockReq(undefined, {
+      headers: { cookie: 'token_provider=openid; openid_user_id=invalid-jwt' },
+      _mockStrategies: {
+        jwt: { user: false, info: { message: 'invalid signature' }, status: 401 },
+        openidJwt: { user: { tenantId: 'tenant-openid', role: 'user' } },
+      },
+    });
+    const res = mockRes();
+    const next = jest.fn();
+
+    requireJwtAuth(req, res, next);
+
+    expect(next).not.toHaveBeenCalled();
+    expect(res.status).toHaveBeenCalledWith(401);
+    expect(req.authStrategy).toBeUndefined();
+    expect(passport.authenticate).toHaveBeenCalledTimes(1);
+    expect(passport.authenticate).toHaveBeenCalledWith(
+      'jwt',
+      { session: false },
+      expect.any(Function),
+    );
   });
 
   it('skips OpenID JWT fallback when the strategy was not registered', async () => {
diff --git a/api/server/middleware/requireJwtAuth.js b/api/server/middleware/requireJwtAuth.js
index 5a9e21b6d3..2820de5359 100644
--- a/api/server/middleware/requireJwtAuth.js
+++ b/api/server/middleware/requireJwtAuth.js
@@ -1,10 +1,29 @@
 const cookies = require('cookie');
+const jwt = require('jsonwebtoken');
 const passport = require('passport');
 const { isEnabled, tenantContextMiddleware } = require('@librechat/api');
 
 const hasPassportStrategy = (strategy) =>
   typeof passport._strategy === 'function' && passport._strategy(strategy) != null;
 
+const getValidOpenIdReuseUserId = (parsedCookies) => {
+  const openidUserId = parsedCookies.openid_user_id;
+  if (!openidUserId || !process.env.JWT_REFRESH_SECRET) {
+    return null;
+  }
+
+  try {
+    const payload = jwt.verify(openidUserId, process.env.JWT_REFRESH_SECRET);
+    return typeof payload === 'object' && payload != null && typeof payload.id === 'string'
+      ? payload.id
+      : null;
+  } catch {
+    return null;
+  }
+};
+
+const getAuthenticatedUserId = (user) => user?.id?.toString?.() ?? user?._id?.toString?.();
+
 /**
  * Custom Middleware to handle JWT authentication, with support for OpenID token reuse.
  * Switches between JWT and OpenID authentication based on cookies and environment settings.
@@ -15,13 +34,14 @@ const hasPassportStrategy = (strategy) =>
  */
 const requireJwtAuth = (req, res, next) => {
   const cookieHeader = req.headers.cookie;
-  const tokenProvider = cookieHeader ? cookies.parse(cookieHeader).token_provider : null;
+  const parsedCookies = cookieHeader ? cookies.parse(cookieHeader) : {};
+  const tokenProvider = parsedCookies.token_provider;
   const openidReuseEnabled = isEnabled(process.env.OPENID_REUSE_TOKENS);
   const openidJwtAvailable = openidReuseEnabled && hasPassportStrategy('openidJwt');
-  const strategies =
-    tokenProvider === 'openid' && openidJwtAvailable
-      ? ['openidJwt', 'jwt']
-      : ['jwt', ...(openidJwtAvailable ? ['openidJwt'] : [])];
+  const openIdReuseUserId = getValidOpenIdReuseUserId(parsedCookies);
+  const useOpenIdJwt =
+    tokenProvider === 'openid' && openidJwtAvailable && openIdReuseUserId != null;
+  const strategies = useOpenIdJwt ? ['openidJwt', 'jwt'] : ['jwt'];
 
   const authenticateWithStrategy = (index) => {
     const strategy = strategies[index];
@@ -37,6 +57,12 @@ const requireJwtAuth = (req, res, next) => {
           message: info?.message || 'Unauthorized',
         });
       }
+      if (strategy === 'openidJwt' && getAuthenticatedUserId(user) !== openIdReuseUserId) {
+        if (index + 1 < strategies.length) {
+          return authenticateWithStrategy(index + 1);
+        }
+        return res.status(401).json({ message: 'Unauthorized' });
+      }
       req.user = user;
       req.authStrategy = strategy;
       // req.user is now populated by passport — set up tenant ALS context
diff --git a/api/strategies/openIdJwtStrategy.js b/api/strategies/openIdJwtStrategy.js
index 8af11bf99c..78145f1109 100644
--- a/api/strategies/openIdJwtStrategy.js
+++ b/api/strategies/openIdJwtStrategy.js
@@ -9,10 +9,40 @@ const {
   findOpenIDUser,
   getOpenIdEmail,
   getOpenIdIssuer,
+  normalizeOpenIdIssuer,
   math,
 } = require('@librechat/api');
 const { updateUser, findUser } = require('~/models');
 
+const getOpenIdJwtAudience = () => {
+  const audiences = [process.env.OPENID_CLIENT_ID, process.env.OPENID_AUDIENCE].filter(Boolean);
+  const uniqueAudiences = [...new Set(audiences)];
+
+  return uniqueAudiences.length > 1 ? uniqueAudiences : uniqueAudiences[0];
+};
+
+const escapeRegExp = (value) => value.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+
+const issuerMatchesTemplate = (expectedIssuer, actualIssuer) => {
+  if (!expectedIssuer.includes('{tenantid}')) {
+    return false;
+  }
+
+  const escapedTemplate = expectedIssuer.split('{tenantid}').map(escapeRegExp).join('[^/]+');
+  return new RegExp(`^${escapedTemplate}$`).test(actualIssuer);
+};
+
+const isOpenIdIssuerAllowed = (payload, openIdConfig) => {
+  const actualIssuer = normalizeOpenIdIssuer(payload?.iss);
+  const expectedIssuer = normalizeOpenIdIssuer(openIdConfig.serverMetadata().issuer);
+
+  if (!actualIssuer || !expectedIssuer) {
+    return false;
+  }
+
+  return actualIssuer === expectedIssuer || issuerMatchesTemplate(expectedIssuer, actualIssuer);
+};
+
 /**
  * @function openIdJwtLogin
  * @param {import('openid-client').Configuration} openIdConfig - Configuration object for the JWT strategy.
@@ -47,6 +77,7 @@ const openIdJwtLogin = (openIdConfig) => {
     {
       jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
       secretOrKeyProvider: jwksRsa.passportJwtSecret(jwksRsaOptions),
+      audience: getOpenIdJwtAudience(),
       passReqToCallback: true,
     },
     /**
@@ -56,6 +87,11 @@ const openIdJwtLogin = (openIdConfig) => {
      */
     async (req, payload, done) => {
       try {
+        if (!isOpenIdIssuerAllowed(payload, openIdConfig)) {
+          done(null, false, { message: 'Invalid issuer' });
+          return;
+        }
+
         const authHeader = req.headers.authorization;
         const rawToken = authHeader?.replace('Bearer ', '');
         const openidIssuer = getOpenIdIssuer(payload, openIdConfig);
diff --git a/api/strategies/openIdJwtStrategy.spec.js b/api/strategies/openIdJwtStrategy.spec.js
index e3bc9f6e28..59229a3d15 100644
--- a/api/strategies/openIdJwtStrategy.spec.js
+++ b/api/strategies/openIdJwtStrategy.spec.js
@@ -1,9 +1,11 @@
 const { SystemRoles } = require('librechat-data-provider');
 
-// --- Capture the verify callback from JwtStrategy ---
+// --- Capture JwtStrategy inputs ---
+let capturedStrategyOptions;
 let capturedVerifyCallback;
 jest.mock('passport-jwt', () => ({
-  Strategy: jest.fn((_opts, verifyCallback) => {
+  Strategy: jest.fn((opts, verifyCallback) => {
+    capturedStrategyOptions = opts;
     capturedVerifyCallback = verifyCallback;
     return { name: 'jwt' };
   }),
@@ -25,6 +27,7 @@ jest.mock('@librechat/api', () => ({
   findOpenIDUser: jest.fn(),
   getOpenIdEmail: jest.requireActual('@librechat/api').getOpenIdEmail,
   getOpenIdIssuer: jest.fn(() => 'https://issuer.example.com'),
+  normalizeOpenIdIssuer: jest.requireActual('@librechat/api').normalizeOpenIdIssuer,
   math: jest.fn((val, fallback) => fallback),
 }));
 jest.mock('~/models', () => ({
@@ -47,6 +50,28 @@ const { findOpenIDUser } = require('@librechat/api');
 const openIdJwtLogin = require('./openIdJwtStrategy');
 const { findUser, updateUser } = require('~/models');
 
+function withEnv(env, callback) {
+  const previous = Object.fromEntries(Object.keys(env).map((key) => [key, process.env[key]]));
+  Object.entries(env).forEach(([key, value]) => {
+    if (value === undefined) {
+      delete process.env[key];
+      return;
+    }
+    process.env[key] = value;
+  });
+  try {
+    callback();
+  } finally {
+    Object.entries(previous).forEach(([key, value]) => {
+      if (value === undefined) {
+        delete process.env[key];
+        return;
+      }
+      process.env[key] = value;
+    });
+  }
+}
+
 // Helper: build a mock openIdConfig
 const mockOpenIdConfig = {
   serverMetadata: () => ({
@@ -67,6 +92,79 @@ async function invokeVerify(req, payload) {
   });
 }
 
+describe('openIdJwtStrategy – token validation', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('requires OpenID JWTs to match the configured client audience and issuer', () => {
+    withEnv({ OPENID_CLIENT_ID: 'librechat-client-id', OPENID_AUDIENCE: undefined }, () => {
+      openIdJwtLogin(mockOpenIdConfig);
+    });
+
+    expect(capturedStrategyOptions).toMatchObject({
+      audience: 'librechat-client-id',
+      passReqToCallback: true,
+    });
+    expect(capturedStrategyOptions).not.toHaveProperty('issuer');
+  });
+
+  it('also accepts OPENID_AUDIENCE for providers that mint resource-bound JWTs', () => {
+    withEnv({ OPENID_CLIENT_ID: 'librechat-client-id', OPENID_AUDIENCE: 'api://librechat' }, () => {
+      openIdJwtLogin(mockOpenIdConfig);
+    });
+
+    expect(capturedStrategyOptions).toMatchObject({
+      audience: ['librechat-client-id', 'api://librechat'],
+    });
+  });
+
+  it('rejects OpenID JWTs whose issuer does not match the configured issuer', async () => {
+    findOpenIDUser.mockResolvedValue({ user: null, error: null, migration: false });
+    openIdJwtLogin(mockOpenIdConfig);
+
+    const req = { headers: { authorization: 'Bearer tok' }, session: {} };
+    const { user, info } = await invokeVerify(req, {
+      sub: 'oidc-123',
+      email: 'test@example.com',
+      iss: 'https://other-issuer.example.com',
+      exp: 9999999999,
+    });
+
+    expect(user).toBe(false);
+    expect(info).toEqual({ message: 'Invalid issuer' });
+    expect(findOpenIDUser).not.toHaveBeenCalled();
+  });
+
+  it('allows Microsoft Entra tenant issuer values for tenant-independent metadata', async () => {
+    const entraConfig = {
+      serverMetadata: () => ({
+        issuer: 'https://login.microsoftonline.com/{tenantid}/v2.0',
+        jwks_uri: 'https://login.microsoftonline.com/common/discovery/v2.0/keys',
+      }),
+    };
+    const user = {
+      _id: { toString: () => 'user-abc' },
+      role: SystemRoles.USER,
+      provider: 'openid',
+    };
+    findOpenIDUser.mockResolvedValue({ user, error: null, migration: false });
+    updateUser.mockResolvedValue({});
+    openIdJwtLogin(entraConfig);
+
+    const req = { headers: { authorization: 'Bearer tok' }, session: {} };
+    const { user: result } = await invokeVerify(req, {
+      sub: 'oidc-123',
+      email: 'test@example.com',
+      iss: 'https://login.microsoftonline.com/11111111-2222-3333-4444-555555555555/v2.0',
+      exp: 9999999999,
+    });
+
+    expect(result).toBeTruthy();
+    expect(findOpenIDUser).toHaveBeenCalled();
+  });
+});
+
 describe('openIdJwtStrategy – token source handling', () => {
   const baseUser = {
     _id: { toString: () => 'user-abc' },
@@ -74,7 +172,12 @@ describe('openIdJwtStrategy – token source handling', () => {
     provider: 'openid',
   };
 
-  const payload = { sub: 'oidc-123', email: 'test@example.com', exp: 9999999999 };
+  const payload = {
+    sub: 'oidc-123',
+    email: 'test@example.com',
+    iss: 'https://issuer.example.com',
+    exp: 9999999999,
+  };
 
   beforeEach(() => {
     jest.clearAllMocks();
@@ -204,6 +307,7 @@ describe('openIdJwtStrategy – OPENID_EMAIL_CLAIM', () => {
     email: 'test@example.com',
     preferred_username: 'testuser',
     upn: 'test@corp.example.com',
+    iss: 'https://issuer.example.com',
     exp: 9999999999,
   };
 
@@ -349,6 +453,7 @@ describe('openIdJwtStrategy – OPENID_EMAIL_CLAIM', () => {
       sub: 'oidc-new-sub',
       preferred_username: 'legacy@corp.com',
       upn: 'legacy@corp.com',
+      iss: 'https://issuer.example.com',
       exp: 9999999999,
     };