diff --git a/packages/backend/src/routes/auth/index.ts b/packages/backend/src/routes/auth/index.ts
index 1c0c2d2..d2a7d45 100644
--- a/packages/backend/src/routes/auth/index.ts
+++ b/packages/backend/src/routes/auth/index.ts
@@ -12,6 +12,14 @@ import { createJwtAuthMiddleware } from '../../middleware/jwt-auth.middleware';
 import type { AppServiceMap } from '../../services';
 import type { ServiceProvider } from '../../services/app.services';
 
+// OAuth state data structure
+interface OAuthStateData {
+  device_code?: string;
+  desktop?: boolean;
+  callback?: string;
+  include_provider_token?: boolean;
+}
+
 export const getAuthRouter = (serviceProvider: ServiceProvider<AppServiceMap>) => {
   const router = Router();
 
@@ -38,14 +46,27 @@ export const getAuthRouter = (serviceProvider: ServiceProvider<AppServiceMap>) =
       // Store device code in session state if coming from device flow
       const deviceUserCode = req.query.device_code as string | undefined;
 
+      // Desktop OAuth parameters
+      const desktop = req.query.desktop === 'true';
+      const callback = req.query.callback as string | undefined;
+      const includeProviderToken = req.query.include_provider_token === 'true';
+
       logger.info('GitHub OAuth initiated', {
         ip: req.ip,
         userAgent: req.get('User-Agent'),
         isDeviceFlow: !!deviceUserCode,
+        isDesktop: desktop,
       });
 
-      // Pass device code via state parameter
-      const state = deviceUserCode ? JSON.stringify({ device_code: deviceUserCode }) : undefined;
+      // Build state parameter with all flow information
+      const stateData: OAuthStateData = {};
+      if (deviceUserCode) stateData.device_code = deviceUserCode;
+      if (desktop) {
+        stateData.desktop = true;
+        stateData.callback = callback;
+        stateData.include_provider_token = includeProviderToken;
+      }
+      const state = Object.keys(stateData).length > 0 ? JSON.stringify(stateData) : undefined;
 
       passport.authenticate('github', {
         scope: ['user:email'],
@@ -81,25 +102,58 @@ export const getAuthRouter = (serviceProvider: ServiceProvider<AppServiceMap>) =
           email: req.user.email,
         });
 
-        // Check if this is from device flow
-        let deviceUserCode: string | undefined;
+        // Parse state parameter for flow information
+        let stateData: OAuthStateData = {};
         try {
           const state = req.query.state as string;
           if (state) {
-            const stateData = JSON.parse(state);
-            deviceUserCode = stateData.device_code;
+            stateData = JSON.parse(state) as OAuthStateData;
           }
         } catch {
-          // Not a device flow or invalid state
+          // Invalid or missing state
         }
 
         const frontendFqdn = config.get('FRONTEND_FQDN', 'localhost:3000');
         const protocol = process.env.NODE_ENV === 'production' ? 'https' : 'http';
 
-        if (deviceUserCode) {
+        // Check for desktop flow
+        if (stateData.desktop && stateData.callback) {
+          // Validate callback is localhost
+          try {
+            const callbackUrl = new URL(stateData.callback);
+            if (callbackUrl.hostname !== 'localhost' && callbackUrl.hostname !== '127.0.0.1') {
+              logger.warn('Invalid desktop callback URL - not localhost', {
+                callback: stateData.callback,
+              });
+              return res.status(400).json({ error: 'Invalid callback URL - must be localhost' });
+            }
+
+            // Build redirect URL with token
+            callbackUrl.searchParams.set('token', token);
+
+            // Include provider token if requested
+            if (stateData.include_provider_token && req.user.providerToken) {
+              callbackUrl.searchParams.set('github_token', req.user.providerToken);
+            }
+
+            logger.info('Redirecting to desktop callback', { callback: callbackUrl.toString() });
+            return res.redirect(callbackUrl.toString());
+          } catch (error) {
+            logger.error('Error parsing desktop callback URL', {
+              error,
+              callback: stateData.callback,
+            });
+            return res.status(400).json({ error: 'Invalid callback URL format' });
+          }
+        }
+
+        // Check if this is from device flow
+        if (stateData.device_code) {
           // Redirect to device authorization page with token
-          const redirectUrl = `${protocol}://${frontendFqdn}/device/authorize?token=${token}&code=${deviceUserCode}`;
-          logger.info('Redirecting to device authorization', { deviceUserCode });
+          const redirectUrl = `${protocol}://${frontendFqdn}/device/authorize?token=${token}&code=${stateData.device_code}`;
+          logger.info('Redirecting to device authorization', {
+            deviceUserCode: stateData.device_code,
+          });
           return res.redirect(redirectUrl);
         }
 
@@ -119,12 +173,31 @@ export const getAuthRouter = (serviceProvider: ServiceProvider<AppServiceMap>) =
   router.get('/google', async (req: Request, res: Response, next) => {
     try {
       const logger = await serviceProvider.get('logger');
+
+      // Desktop OAuth parameters
+      const desktop = req.query.desktop === 'true';
+      const callback = req.query.callback as string | undefined;
+      const includeProviderToken = req.query.include_provider_token === 'true';
+
       logger.info('Google OAuth initiated', {
         ip: req.ip,
         userAgent: req.get('User-Agent'),
+        isDesktop: desktop,
       });
 
-      passport.authenticate('google', { scope: ['profile', 'email'] })(req, res, next);
+      // Build state parameter with desktop flow information
+      const stateData: OAuthStateData = {};
+      if (desktop) {
+        stateData.desktop = true;
+        stateData.callback = callback;
+        stateData.include_provider_token = includeProviderToken;
+      }
+      const state = Object.keys(stateData).length > 0 ? JSON.stringify(stateData) : undefined;
+
+      passport.authenticate('google', {
+        scope: ['profile', 'email'],
+        state,
+      })(req, res, next);
     } catch (error) {
       next(error);
     }
@@ -155,9 +228,52 @@ export const getAuthRouter = (serviceProvider: ServiceProvider<AppServiceMap>) =
           email: req.user.email,
         });
 
-        // Redirect to frontend with token
+        // Parse state parameter for flow information
+        let stateData: OAuthStateData = {};
+        try {
+          const state = req.query.state as string;
+          if (state) {
+            stateData = JSON.parse(state) as OAuthStateData;
+          }
+        } catch {
+          // Invalid or missing state
+        }
+
         const frontendFqdn = config.get('FRONTEND_FQDN', 'localhost:3000');
         const protocol = process.env.NODE_ENV === 'production' ? 'https' : 'http';
+
+        // Check for desktop flow
+        if (stateData.desktop && stateData.callback) {
+          // Validate callback is localhost
+          try {
+            const callbackUrl = new URL(stateData.callback);
+            if (callbackUrl.hostname !== 'localhost' && callbackUrl.hostname !== '127.0.0.1') {
+              logger.warn('Invalid desktop callback URL - not localhost', {
+                callback: stateData.callback,
+              });
+              return res.status(400).json({ error: 'Invalid callback URL - must be localhost' });
+            }
+
+            // Build redirect URL with token
+            callbackUrl.searchParams.set('token', token);
+
+            // Include provider token if requested
+            if (stateData.include_provider_token && req.user.providerToken) {
+              callbackUrl.searchParams.set('google_token', req.user.providerToken);
+            }
+
+            logger.info('Redirecting to desktop callback', { callback: callbackUrl.toString() });
+            return res.redirect(callbackUrl.toString());
+          } catch (error) {
+            logger.error('Error parsing desktop callback URL', {
+              error,
+              callback: stateData.callback,
+            });
+            return res.status(400).json({ error: 'Invalid callback URL format' });
+          }
+        }
+
+        // Redirect to frontend with token
         const redirectUrl = `${protocol}://${frontendFqdn}/auth/callback?token=${token}`;
         res.redirect(redirectUrl);
       } catch (error) {
@@ -173,12 +289,31 @@ export const getAuthRouter = (serviceProvider: ServiceProvider<AppServiceMap>) =
   router.get('/microsoft', async (req: Request, res: Response, next) => {
     try {
       const logger = await serviceProvider.get('logger');
+
+      // Desktop OAuth parameters
+      const desktop = req.query.desktop === 'true';
+      const callback = req.query.callback as string | undefined;
+      const includeProviderToken = req.query.include_provider_token === 'true';
+
       logger.info('Microsoft OAuth initiated', {
         ip: req.ip,
         userAgent: req.get('User-Agent'),
+        isDesktop: desktop,
       });
 
-      passport.authenticate('microsoft', { scope: ['user.read'] })(req, res, next);
+      // Build state parameter with desktop flow information
+      const stateData: OAuthStateData = {};
+      if (desktop) {
+        stateData.desktop = true;
+        stateData.callback = callback;
+        stateData.include_provider_token = includeProviderToken;
+      }
+      const state = Object.keys(stateData).length > 0 ? JSON.stringify(stateData) : undefined;
+
+      passport.authenticate('microsoft', {
+        scope: ['user.read'],
+        state,
+      })(req, res, next);
     } catch (error) {
       next(error);
     }
@@ -209,9 +344,52 @@ export const getAuthRouter = (serviceProvider: ServiceProvider<AppServiceMap>) =
           email: req.user.email,
         });
 
-        // Redirect to frontend with token
+        // Parse state parameter for flow information
+        let stateData: OAuthStateData = {};
+        try {
+          const state = req.query.state as string;
+          if (state) {
+            stateData = JSON.parse(state) as OAuthStateData;
+          }
+        } catch {
+          // Invalid or missing state
+        }
+
         const frontendFqdn = config.get('FRONTEND_FQDN', 'localhost:3000');
         const protocol = process.env.NODE_ENV === 'production' ? 'https' : 'http';
+
+        // Check for desktop flow
+        if (stateData.desktop && stateData.callback) {
+          // Validate callback is localhost
+          try {
+            const callbackUrl = new URL(stateData.callback);
+            if (callbackUrl.hostname !== 'localhost' && callbackUrl.hostname !== '127.0.0.1') {
+              logger.warn('Invalid desktop callback URL - not localhost', {
+                callback: stateData.callback,
+              });
+              return res.status(400).json({ error: 'Invalid callback URL - must be localhost' });
+            }
+
+            // Build redirect URL with token
+            callbackUrl.searchParams.set('token', token);
+
+            // Include provider token if requested
+            if (stateData.include_provider_token && req.user.providerToken) {
+              callbackUrl.searchParams.set('microsoft_token', req.user.providerToken);
+            }
+
+            logger.info('Redirecting to desktop callback', { callback: callbackUrl.toString() });
+            return res.redirect(callbackUrl.toString());
+          } catch (error) {
+            logger.error('Error parsing desktop callback URL', {
+              error,
+              callback: stateData.callback,
+            });
+            return res.status(400).json({ error: 'Invalid callback URL format' });
+          }
+        }
+
+        // Redirect to frontend with token
         const redirectUrl = `${protocol}://${frontendFqdn}/auth/callback?token=${token}`;
         res.redirect(redirectUrl);
       } catch (error) {
diff --git a/packages/backend/src/services/oauth/oauth.service.ts b/packages/backend/src/services/oauth/oauth.service.ts
index 4e5018d..8787b7d 100644
--- a/packages/backend/src/services/oauth/oauth.service.ts
+++ b/packages/backend/src/services/oauth/oauth.service.ts
@@ -1,10 +1,18 @@
 import passport from 'passport';
-import { Strategy as GitHubStrategy } from 'passport-github2';
-import { Strategy as GoogleStrategy } from 'passport-google-oauth20';
+import { Profile as GitHubProfile, Strategy as GitHubStrategy } from 'passport-github2';
+import { Profile as GoogleProfile, Strategy as GoogleStrategy } from 'passport-google-oauth20';
 import { Strategy as MicrosoftStrategy } from 'passport-microsoft';
 import type { ConfigService, LoggerService, Service } from '../app.services';
 import type { UserService } from '../user';
 
+// Microsoft profile interface (passport-microsoft doesn't export Profile type)
+interface MicrosoftProfile {
+  id: string;
+  displayName?: string;
+  emails?: Array<{ value: string }>;
+  photos?: Array<{ value: string }>;
+}
+
 export interface OAuthService extends Service {
   /**
    * Configure all OAuth strategies
@@ -40,9 +48,9 @@ export const createOAuthService = (
               scope: ['user:email'],
             },
             async (
-              _accessToken: string,
+              accessToken: string,
               _refreshToken: string,
-              profile: any,
+              profile: GitHubProfile,
               done: (error: Error | null, user?: Express.User | false) => void
             ) => {
               try {
@@ -71,6 +79,7 @@ export const createOAuthService = (
                   role: userDoc.role,
                   createdAt: userDoc.createdAt,
                   updatedAt: userDoc.updatedAt,
+                  providerToken: accessToken, // Store provider token for desktop flow
                 };
 
                 logger.info('GitHub OAuth successful', {
@@ -107,7 +116,12 @@ export const createOAuthService = (
               callbackURL: googleCallbackUrl,
               scope: ['profile', 'email'],
             },
-            async (_accessToken, _refreshToken, profile, done) => {
+            async (
+              accessToken: string,
+              _refreshToken: string,
+              profile: GoogleProfile,
+              done: (error: Error | null, user?: Express.User | false) => void
+            ) => {
               try {
                 const email = profile.emails?.[0]?.value;
                 if (!email) {
@@ -133,6 +147,7 @@ export const createOAuthService = (
                   role: userDoc.role,
                   createdAt: userDoc.createdAt,
                   updatedAt: userDoc.updatedAt,
+                  providerToken: accessToken, // Store provider token for desktop flow
                 };
 
                 logger.info('Google OAuth successful', {
@@ -175,9 +190,9 @@ export const createOAuthService = (
               scope: ['user.read'],
             },
             async (
-              _accessToken: string,
+              accessToken: string,
               _refreshToken: string,
-              profile: any,
+              profile: MicrosoftProfile,
               done: (error: Error | null, user?: Express.User | false) => void
             ) => {
               try {
@@ -205,6 +220,7 @@ export const createOAuthService = (
                   role: userDoc.role,
                   createdAt: userDoc.createdAt,
                   updatedAt: userDoc.updatedAt,
+                  providerToken: accessToken, // Store provider token for desktop flow
                 };
 
                 logger.info('Microsoft OAuth successful', {
diff --git a/packages/backend/src/types/express.d.ts b/packages/backend/src/types/express.d.ts
index 80f17f8..5c48652 100644
--- a/packages/backend/src/types/express.d.ts
+++ b/packages/backend/src/types/express.d.ts
@@ -39,6 +39,9 @@ declare global {
         };
       };
 
+      // Provider token (for desktop OAuth flow)
+      providerToken?: string;
+
       // Authorization
       role: 'user' | 'admin';
 
diff --git a/packages/frontend/src/app/desktop-login/page.tsx b/packages/frontend/src/app/desktop-login/page.tsx
new file mode 100644
index 0000000..bd84071
--- /dev/null
+++ b/packages/frontend/src/app/desktop-login/page.tsx
@@ -0,0 +1,116 @@
+'use client';
+
+import Link from 'next/link';
+import { useSearchParams } from 'next/navigation';
+import { Suspense } from 'react';
+import { LoginButton } from '../../components/auth/LoginButton';
+
+function DesktopLoginContent() {
+  const searchParams = useSearchParams();
+  const callback = searchParams.get('callback') || 'http://localhost:3739/callback';
+
+  const handleLogin = (provider: 'google' | 'github' | 'microsoft') => {
+    const params = new URLSearchParams({
+      desktop: 'true',
+      callback,
+      include_provider_token: 'true',
+    });
+
+    window.location.href = `/api/auth/${provider}?${params.toString()}`;
+  };
+
+  return (
+    <div className="min-h-screen flex items-center justify-center bg-gradient-to-br from-blue-50 to-indigo-100 p-4">
+      <div className="bg-white rounded-2xl shadow-2xl max-w-md w-full p-8">
+        {/* Header */}
+        <div className="text-center mb-8">
+          <div className="inline-flex items-center justify-center w-16 h-16 bg-blue-600 rounded-full mb-4">
+            <svg
+              className="w-8 h-8 text-white"
+              fill="none"
+              stroke="currentColor"
+              viewBox="0 0 24 24"
+            >
+              <path
+                strokeLinecap="round"
+                strokeLinejoin="round"
+                strokeWidth={2}
+                d="M9.75 17L9 20l-1 1h8l-1-1-.75-3M3 13h18M5 17h14a2 2 0 002-2V5a2 2 0 00-2-2H5a2 2 0 00-2 2v10a2 2 0 002 2z"
+              />
+            </svg>
+          </div>
+          <h1 className="text-3xl font-bold text-gray-900 mb-2">Sign in to Agentage Desktop</h1>
+          <p className="text-gray-600">Choose your preferred authentication method</p>
+        </div>
+
+        {/* Login Buttons */}
+        <div className="space-y-3 mb-6">
+          <LoginButton provider="google" onClick={() => handleLogin('google')} className="w-full" />
+          <LoginButton provider="github" onClick={() => handleLogin('github')} className="w-full" />
+          <LoginButton
+            provider="microsoft"
+            onClick={() => handleLogin('microsoft')}
+            className="w-full"
+          />
+        </div>
+
+        {/* Info Box */}
+        <div className="bg-blue-50 border border-blue-200 rounded-lg p-4 mb-6">
+          <div className="flex items-start">
+            <svg
+              className="w-5 h-5 text-blue-600 mt-0.5 mr-3 flex-shrink-0"
+              fill="none"
+              stroke="currentColor"
+              viewBox="0 0 24 24"
+            >
+              <path
+                strokeLinecap="round"
+                strokeLinejoin="round"
+                strokeWidth={2}
+                d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"
+              />
+            </svg>
+            <div>
+              <p className="text-sm text-blue-800 font-medium mb-1">
+                Secure Desktop Authentication
+              </p>
+              <p className="text-xs text-blue-700">
+                After signing in, you'll be redirected back to the Agentage Desktop application on
+                your computer.
+              </p>
+            </div>
+          </div>
+        </div>
+
+        {/* Terms */}
+        <p className="text-xs text-gray-500 text-center">
+          By signing in, you agree to our{' '}
+          <Link href="/terms" className="text-blue-600 hover:underline">
+            Terms of Service
+          </Link>{' '}
+          and{' '}
+          <Link href="/privacy" className="text-blue-600 hover:underline">
+            Privacy Policy
+          </Link>
+        </p>
+      </div>
+    </div>
+  );
+}
+
+export default function DesktopLoginPage() {
+  return (
+    <Suspense
+      fallback={
+        <div className="min-h-screen flex items-center justify-center bg-gradient-to-br from-blue-50 to-indigo-100">
+          <div className="text-center">
+            <div className="inline-block animate-spin rounded-full h-12 w-12 border-b-2 border-blue-600 mb-4"></div>
+            <p className="text-gray-600 text-lg">Loading...</p>
+          </div>
+        </div>
+      }
+    >
+      <DesktopLoginContent />
+    </Suspense>
+  );
+}