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FastAPI AI Kit
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Better Auth Integration

Layer Better Auth in front of the kit's API when you need social/passkey login.

FastAPI AI Kit's built-in auth is JWT + API keys, aimed at API-to-API and programmatic access. Better Auth is a TypeScript auth library for user-facing sign-in flows (OAuth, passkeys, magic links). The two solve different problems and typically sit at different layers.

Setup in 4 steps

  1. 1Run Better Auth in your Next.js/Node frontend for user sign-in (OAuth, passkeys, email)
  2. 2After sign-in, have your frontend exchange the Better Auth session for a kit-issued API key or short-lived JWT
  3. 3The FastAPI backend keeps validating its own JWT/API keys — no auth library needed on the Python side
  4. 4Map Better Auth user IDs to the kit's API key records for per-user usage tracking

What's included

  • Keeps user-facing auth (social login, passkeys) in the frontend where Better Auth is strongest
  • Keeps API auth (rate limiting, billing, per-key tiers) in the kit where it's already built
  • No need to reimplement OAuth flows in Python
  • Per-user Stripe metering still works — you just map Better Auth's user ID to a kit API key

Code example

example.py
// Frontend: after Better Auth sign-in, mint a kit API key
const session = await auth.api.getSession({ headers });
const res = await fetch("/internal/api-keys/issue", {
  method: "POST",
  body: JSON.stringify({ external_user_id: session.user.id }),
});
const { api_key } = await res.json();
// Use api_key for subsequent calls to the FastAPI AI Kit backend

Full documentation: /docs/authentication

Better Auth integration pre-wired and ready.

FastAPI AI Kit ships with Better Auth configured out of the box. No manual setup required.

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