Agent Skills: Better Auth Core (TypeScript)

Better Auth Core (TypeScript)

Goals

• Set up a Better Auth instance with environment variables and data layer wiring.
• Wire server handlers and a client instance.
• Use sessions and server-side API methods safely.
• Keep data-layer choices pluggable (drivers or adapters).

Quick start

1. Install better-auth.
2. Set BETTER_AUTH_SECRET (32+ chars) and BETTER_AUTH_URL.
3. Create auth.ts and export auth.
4. Provide database (driver or adapter) or omit for stateless sessions.
5. Mount a handler (auth.handler or a framework helper).
6. Create a client with createAuthClient.

import { betterAuth } from "better-auth";

export const auth = betterAuth({
  database: myDatabaseOrAdapter, // driver or adapter; omit for stateless mode
  emailAndPassword: { enabled: true },
  socialProviders: {
    github: {
      clientId: process.env.GITHUB_CLIENT_ID as string,
      clientSecret: process.env.GITHUB_CLIENT_SECRET as string,
    },
  },
});

Core setup checklist

• Export the instance as auth (or default export) so helpers find it.
• Keep BETTER_AUTH_URL in sync with the public base URL.
• Pass the full base URL to the client if you change the /api/auth base path.
• Add database migrations before enabling plugins that require tables.

Server API usage

• Call server endpoints via auth.api.* with { body, headers, query }.
• Use asResponse: true if you need a Response object.
• Use returnHeaders: true to access Set-Cookie headers.

import { auth } from "./auth";

const session = await auth.api.getSession({
  headers: request.headers,
});

const response = await auth.api.signInEmail({
  body: { email, password },
  asResponse: true,
});

Session access

• Client: authClient.useSession() or authClient.getSession().
• Server: auth.api.getSession({ headers }).

TypeScript tips

• Infer types with auth.$Infer and authClient.$Infer.
• Use inferAdditionalFields on the client when you extend the user schema.

References

• toolchains/platforms/auth/better-auth/better-auth-core/references/setup-database.md
• toolchains/platforms/auth/better-auth/better-auth-core/references/client-server.md
• toolchains/platforms/auth/better-auth/better-auth-core/references/typescript.md