feat: Migrate from NextAuth to Better Auth since the future of Auth.js is clearly Better Auth

README.md

@@ -31,8 +31,9 @@
 - Data Persistence
   - [Neon Serverless Postgres](https://vercel.com/marketplace/neon) for saving chat history and user data
   - [Vercel Blob](https://vercel.com/storage/blob) for efficient file storage
-- [Auth.js](https://authjs.dev)
-  - Simple and secure authentication
+- [BetterAuth](https://www.better-auth.com)
+  - Modern, type-safe authentication with email/password support
+  - Built-in session management with customizable password hashing
 
 ## Model Providers
 

app/(auth)/actions.ts

@@ -1,19 +1,18 @@
-"use server";
+"use server"
 
-import { z } from "zod";
-
-import { createUser, getUser } from "@/lib/db/queries";
-
-import { signIn } from "./auth";
+import { z } from "zod"
+import { auth } from "@/lib/auth"
+import { createUser, getUser } from "@/lib/db/queries"
+import { headers } from "next/headers"
 
 const authFormSchema = z.object({
   email: z.string().email(),
   password: z.string().min(6),
-});
+})
 
 export type LoginActionState = {
-  status: "idle" | "in_progress" | "success" | "failed" | "invalid_data";
-};
+  status: "idle" | "in_progress" | "success" | "failed" | "invalid_data"
+}
 
 export const login = async (
   _: LoginActionState,
@@ -23,23 +22,26 @@ export const login = async (
     const validatedData = authFormSchema.parse({
       email: formData.get("email"),
       password: formData.get("password"),
-    });
+    })
 
-    await signIn("credentials", {
-      email: validatedData.email,
-      password: validatedData.password,
-      redirect: false,
-    });
+    const response = await auth.api.signInEmail({
+      body: validatedData,
+      headers: await headers(),
+      asResponse: true
+    })
 
-    return { status: "success" };
+    if (!response.ok) {
+      return { status: "failed" }
+    }
+
+    return { status: "success" }
   } catch (error) {
     if (error instanceof z.ZodError) {
-      return { status: "invalid_data" };
+      return { status: "invalid_data" }
     }
-
-    return { status: "failed" };
+    return { status: "failed" }
   }
-};
+}
 
 export type RegisterActionState = {
   status:
@@ -48,8 +50,8 @@ export type RegisterActionState = {
     | "success"
     | "failed"
     | "user_exists"
-    | "invalid_data";
-};
+    | "invalid_data"
+}
 
 export const register = async (
   _: RegisterActionState,
@@ -59,26 +61,33 @@ export const register = async (
     const validatedData = authFormSchema.parse({
       email: formData.get("email"),
       password: formData.get("password"),
-    });
+    })
 
-    const [user] = await getUser(validatedData.email);
+    // Check if user exists
+    const [existingUser] = await getUser(validatedData.email)
+    if (existingUser) {
+      return { status: "user_exists" }
+    }
+
+    // Create user in database first
+    await createUser(validatedData.email, validatedData.password)
 
-    if (user) {
-      return { status: "user_exists" } as RegisterActionState;
+    // Then sign them in
+    const response = await auth.api.signInEmail({
+      body: validatedData,
+      headers: await headers(),
+      asResponse: true
+    })
+
+    if (!response.ok) {
+      return { status: "failed" }
     }
-    await createUser(validatedData.email, validatedData.password);
-    await signIn("credentials", {
-      email: validatedData.email,
-      password: validatedData.password,
-      redirect: false,
-    });
 
-    return { status: "success" };
+    return { status: "success" }
   } catch (error) {
     if (error instanceof z.ZodError) {
-      return { status: "invalid_data" };
+      return { status: "invalid_data" }
     }
-
-    return { status: "failed" };
+    return { status: "failed" }
   }
-};
+}

app/(auth)/api/auth/guest/route.ts

@@ -1,21 +1,51 @@
-import { NextResponse } from "next/server";
-import { getToken } from "next-auth/jwt";
-import { signIn } from "@/app/(auth)/auth";
-import { isDevelopmentEnvironment } from "@/lib/constants";
+import { headers } from "next/headers";
+import { NextResponse } from "next/server"
+import { auth } from "@/lib/auth"
+import { createGuestUser } from "@/lib/db/queries"
 
 export async function GET(request: Request) {
-  const { searchParams } = new URL(request.url);
-  const redirectUrl = searchParams.get("redirectUrl") || "/";
+  const { searchParams } = new URL(request.url)
+  const redirectUrl = searchParams.get("redirectUrl") || "/"
 
-  const token = await getToken({
-    req: request,
-    secret: process.env.AUTH_SECRET,
-    secureCookie: !isDevelopmentEnvironment,
-  });
+  try {
+    // Check if already authenticated
+    const session = await auth.api.getSession({
+      headers: request.headers
+    })
 
-  if (token) {
-    return NextResponse.redirect(new URL("/", request.url));
-  }
+    if (session) {
+      return NextResponse.redirect(new URL("/", request.url))
+    }
+
+    // Create guest user
+    const [guestUser] = await createGuestUser()
+
+    // Sign in the guest user programmatically
+    // This approach manually creates a session for the guest user
+    const signInResponse = await auth.api.signInEmail({
+      body: {
+        email: guestUser.email!,
+        password: "guest-password", // Use a consistent guest password
+      },
+      asResponse: true
+    })
+
+    if (signInResponse.ok) {
+      // Forward the session cookies from the sign-in response
+      const response = NextResponse.redirect(new URL(redirectUrl, request.url))
 
-  return signIn("guest", { redirect: true, redirectTo: redirectUrl });
+      // Copy auth cookies from the sign-in response
+      const authCookies = signInResponse.headers.get('set-cookie')
+      if (authCookies) {
+        response.headers.set('set-cookie', authCookies)
+      }
+
+      return response
+    }
+
+    throw new Error('Guest sign-in failed')
+  } catch (error) {
+    console.error('Guest authentication error:', error)
+    return NextResponse.redirect(new URL("/login", request.url))
+  }
 }

app/(auth)/login/page.tsx

@@ -2,7 +2,7 @@
 
 import Link from "next/link";
 import { useRouter } from "next/navigation";
-import { useSession } from "next-auth/react";
+import { useSession } from "@/lib/auth-client";
 import { useActionState, useEffect, useState } from "react";
 
 import { AuthForm } from "@/components/auth-form";
@@ -23,7 +23,7 @@ export default function Page() {
     }
   );
 
-  const { update: updateSession } = useSession();
+  const { data: session, isPending } = useSession();
 
   useEffect(() => {
     if (state.status === "failed") {
@@ -38,11 +38,10 @@ export default function Page() {
       });
     } else if (state.status === "success") {
       setIsSuccessful(true);
-      updateSession();
       router.refresh();
     }
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [state.status, router.refresh, updateSession]);
+  }, [state.status, router]);
 
   const handleSubmit = (formData: FormData) => {
     setEmail(formData.get("email") as string);

app/(auth)/register/page.tsx

@@ -2,7 +2,7 @@
 
 import Link from "next/link";
 import { useRouter } from "next/navigation";
-import { useSession } from "next-auth/react";
+import { useSession } from "@/lib/auth-client";
 import { useActionState, useEffect, useState } from "react";
 import { AuthForm } from "@/components/auth-form";
 import { SubmitButton } from "@/components/submit-button";
@@ -22,7 +22,7 @@ export default function Page() {
     }
   );
 
-  const { update: updateSession } = useSession();
+  const { data: session, isPending } = useSession();
 
   useEffect(() => {
     if (state.status === "user_exists") {
@@ -38,11 +38,10 @@ export default function Page() {
       toast({ type: "success", description: "Account created successfully!" });
 
       setIsSuccessful(true);
-      updateSession();
       router.refresh();
     }
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [state.status, router.refresh, updateSession]);
+  }, [state.status, router]);
 
   const handleSubmit = (formData: FormData) => {
     setEmail(formData.get("email") as string);

app/(chat)/api/chat/[id]/stream/route.ts

@@ -1,6 +1,7 @@
+import { headers } from "next/headers";
 import { createUIMessageStream, JsonToSseTransformStream } from "ai";
 import { differenceInSeconds } from "date-fns";
-import { auth } from "@/app/(auth)/auth";
+import { auth } from "@/lib/auth";
 import {
   getChatById,
   getMessagesByChatId,
@@ -28,7 +29,7 @@ export async function GET(
     return new ChatSDKError("bad_request:api").toResponse();
   }
 
-  const session = await auth();
+  const session = await auth.api.getSession({ headers: await headers() });
 
   if (!session?.user) {
     return new ChatSDKError("unauthorized:chat").toResponse();