Better Auth Knowledge Patch

Better Auth Knowledge Patch

Use this skill when implementing, upgrading, debugging, or reviewing Better Auth applications. Start with the quick references below, then load the topic file that matches the task.

Reference index

Breaking changes and migrations

Use the standalone CLI

Run the standalone executable instead of the old package-scoped CLI:

npx auth init
npx auth migrate
npx auth generate --adapter prisma
npx auth upgrade

The distribution is ESM-only. Convert CommonJS loading before upgrading. The CLI refuses to add a required column without a default to a populated table; plan a staged migration instead.

Update extracted package imports

Several features now have dedicated packages:

import { sso } from "@better-auth/sso";
import { scim } from "@better-auth/scim";
import { passkey } from "@better-auth/passkey";
import { apiKey } from "@better-auth/api-key";
import { oauthProvider } from "@better-auth/oauth-provider";

Redis-backed secondary storage is installed from @better-auth/redis-storage. Database adapters also have @better-auth/*-adapter packages; direct adapter imports paired with better-auth/minimal reduce the imported distribution.

Apply schema migrations before serving traffic

Important schema changes include:

• Replace organization member teamId with the teamMembers join table.
• Rename API-key userId to referenceId and add configId.
• Rename OIDC redirectURLs to redirectUrls.
• Migrate legacy OAuth-provider tables, secrets, and token values before switching providers.
• Generate tables for Agent Auth, dynamic organization roles, activity tracking, persisted billing, and managed SCIM connections when enabled.
• Rerun generation or migration after enabling database joins.

Replace removed and renamed APIs

await authClient.requestPasswordReset({ email }); // not forgotPassword
await auth.api.accountInfo({ query });             // GET/query, not POST/body

Use createAdapterFactory instead of createAdapter, afterEmailVerification instead of onEmailVerification, and permissions instead of the organization model's permission field. See the migration reference for removed endpoints, types, exports, callbacks, and adapter-test imports.

Treat post-transaction hooks correctly

Database create.after, update.after, and delete.after hooks run after commit. Put atomic follow-up writes in the adapter operation or transaction, not in an after hook.

Sessions and security

Database-free auth is explicit through omission

Omitting database enables stateless session management. Account data can be kept in a signed cookie, and token/account endpoints remain available:

const auth = betterAuth({
  socialProviders: { google: { clientId, clientSecret } },
  account: { storeAccountCookie: true },
});

When secondary storage is configured, sessions move there by default. Opt into database persistence with storeSessionInDatabase; use preserveSessionInDatabase to retain rows after revocation.

Do not extend freshness by refreshing

Session freshAge is measured from createdAt, not updatedAt. Refreshing cannot keep a session fresh indefinitely. Stateless cookie-cache maxAge is bounded by session expiresIn.

Rotate secrets without invalidating all data

Put the newest key first and retain older keys for decryption:

secrets: [
  { version: 2, value: process.env.AUTH_SECRET_V2! },
  { version: 1, value: process.env.AUTH_SECRET_V1! },
]

Separate CSRF and origin decisions

CSRF and origin validation are independent controls. disableCSRFCheck disables only CSRF defense; disableOriginCheck also disables callback/redirect validation and retains broader legacy disabling behavior. Never trust forwarded host/protocol headers unless a front proxy strips attacker-supplied values.

Encrypt provider tokens when required

Provider access and refresh tokens are plain by default. Prefer the built-in option:

account: { encryptOAuthTokens: true }

OAuth, OIDC, SSO, and SCIM

Build new authorization servers with OAuth Provider

@better-auth/oauth-provider implements OAuth 2.1 and OIDC authorization-code, refresh-token, and client-credentials flows, plus discovery, dynamic registration, consent, introspection, revocation, JWT/JWKS, PKCE policy, and rate limits.

plugins: [
  jwt(),
  oauthProvider({ loginPage: "/sign-in", consentPage: "/consent" }),
]

Mount both well-known metadata handlers at the issuer. A separate API also needs protected-resource metadata and should validate access tokens with verifyAccessToken, a resource client, or introspection for opaque tokens. Missing scopes return an RFC 6750 insufficient_scope challenge that clients can use for escalation.

Retire the legacy MCP authorization server

Move authorization-server duties from the legacy built-in MCP plugin to @better-auth/oauth-provider. Separate MCP resource servers can verify tokens with createMcpAuthClient.

Harden SSO and provisioning

• Allowlist the OIDC discovery URL and every resolved endpoint.
• Keep SAML assertion replay protection and response-correlation validation enabled.
• Require assertion signatures and metadata enforcement where the deployment policy calls for them.
• Export all five SCIM methods: GET, POST, PUT, PATCH, and DELETE.
• Authorize SCIM token issuance and choose hashed, encrypted, or custom token storage.
• Treat managed SCIM connection and credential methods as trusted server-only administration.

Hooks and background work

Use unified middleware

hooks: {
  before: createAuthMiddleware(async (ctx) => inspect(ctx.path)),
  after: createAuthMiddleware(async (ctx) => inspect(ctx.context.returned)),
}

Plugin hooks remain matcher/handler entries. A plugin init() receives the live mutable auth context and may return context keys for other plugins.

Choose fire-and-forget versus required completion

runInBackground() schedules work after the response. runInBackgroundOrAwait() uses the configured background handler, but awaits when none exists. Connect serverless lifetime primitives through advanced.backgroundTasks.handler; expect eventual consistency when database writes are deferred.

Framework integration checks

• Mount Express auth routes before express.json(); Express 5 needs a named wildcard.
• Put nextCookies() last when Server Actions call auth.api directly, and validate full sessions for protected Next.js routes.
• Keep Electron auth state and cookies in the main process and align protocol, callback path, client ID, and trusted origin across server, web, and desktop clients.
• Pair Expo server/client plugins with secure storage; send getCookie() manually for non-client requests.
• Enable Workers AsyncLocalStorage compatibility before constructing auth.
• Follow the custom Set-Cookie bridge for Waku Server Actions.

Agent Auth essentials

Agent Auth separates persistent hosts from runtime agents. Each agent has an Ed25519 key, an immutable delegated/autonomous mode, scoped grants, and short-lived single-use Agent JWTs. Discovery starts at /.well-known/agent-configuration; unsupported major protocol versions must stop the client.

Use @better-auth/agent-auth for registration, approval, grant enforcement, and execution. Run its migration, keep automatic default grants low-risk, use durable secondary storage for replay/JWKS caches in multi-instance deployments, and require fresh sessions or WebAuthn proof of presence for sensitive approvals.

Adapter and plugin reminders

• advanced.database.generateId may delegate selected models to the database by returning false or undefined.
• Raw SQLite, MySQL, and PostgreSQL database instances support native adapter transactions.
• Adapter predicates support per-clause mode: "insensitive".
• Custom session fields are recomputed on every fetch and bypass cookie/secondary caches.
• Passkey registration can run without a session only when the supplied context is securely validated.
• API-key validation consumes limits and budgets; avoid verifying twice before getSession.
• Defining custom admin/user roles replaces built-in grants unless their statements are merged.
• Payment plugins differ sharply in owner/reference semantics, persistence, cancellation, and entitlement lookup; load the payment reference before implementation.