fix: Better Auth integration - map sign-in/email to backend login, exclude auth from rewrites

frontend/next.config.js

@@ -12,8 +12,12 @@ const nextConfig = {
         destination: 'http://localhost:5000/:path*',
       },
       {
-        source: '/api/:path*',
-        destination: 'http://localhost:8000/api/:path*',
+        source: '/api/todos/:path*',
+        destination: 'http://localhost:8000/api/todos/:path*',
+      },
+      {
+        source: '/health',
+        destination: 'http://localhost:8000/health',
       },
     ];
   },

frontend/pages/api/auth/[...all].ts

@@ -1,10 +1,25 @@
 /**
  * Better Auth API route handler.
- * Proxies auth requests to FastAPI backend.
+ * Maps Better Auth endpoints to FastAPI backend auth endpoints.
  */
 import type { NextApiRequest, NextApiResponse } from 'next';
 
-const BACKEND_URL = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:8000';
+const BACKEND_URL = 'http://localhost:8000';
+
+/**
+ * Map Better Auth paths to backend paths.
+ * Better Auth uses: /api/auth/sign-in/email, /api/auth/sign-up/email
+ * Backend uses: /api/auth/login, /api/auth/signup
+ */
+function mapAuthPath(path: string): string {
+  if (path === 'sign-in/email' || path === 'sign-in') {
+    return 'login';
+  }
+  if (path === 'sign-up/email' || path === 'sign-up') {
+    return 'signup';
+  }
+  return path;
+}
 
 export default async function handler(
   req: NextApiRequest,
@@ -12,9 +27,10 @@ export default async function handler(
 ) {
   const { all } = req.query;
   const path = Array.isArray(all) ? all.join('/') : all || '';
+  const mappedPath = mapAuthPath(path);
 
   try {
-    const backendUrl = `${BACKEND_URL}/api/auth/${path}`;
+    const backendUrl = `${BACKEND_URL}/api/auth/${mappedPath}`;
     const response = await fetch(backendUrl, {
       method: req.method || 'GET',
       headers: {
@@ -33,4 +49,4 @@ export default async function handler(
   } catch (error) {
     res.status(500).json({ error: 'Auth service unavailable' });
   }
-}
+}

frontend/pages/login.tsx

@@ -1,9 +1,10 @@
 /**
- * Login page with modern UI - uses backend /api/auth/login endpoint.
+ * Login page with modern UI using Better Auth signIn.email().
  */
 import { useState, FormEvent } from 'react';
 import { useRouter } from 'next/router';
-import { apiCall, setToken } from '@/lib/api';
+import { signIn } from '@/lib/auth';
+import { setToken } from '@/lib/api';
 
 export default function Login() {
   const router = useRouter();
@@ -18,6 +19,20 @@ export default function Login() {
     setLoading(true);
 
     try {
+      // Better Auth signIn - calls /api/auth/sign-in/email
+      // which maps to backend /api/auth/login via [...all].ts
+      const result = await signIn.email({ email, password });
+      if (result?.data?.token) {
+        setToken(result.data.token);
+        router.push('/todos');
+        return;
+      }
+      if (result?.error) {
+        throw new Error(result.error.message || 'Login failed');
+      }
+
+      // Fallback: direct API call to backend
+      const { apiCall } = await import('@/lib/api');
       const response = await apiCall('/api/auth/login', 'POST', { email, password }, false);
       setToken(response.token);
       router.push('/todos');