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better-auth-best-practices skill

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This skill helps integrate Better Auth with TypeScript apps, guiding configuration, plugins, session management, and security best practices.

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---
name: better-auth-best-practices
description: Skill for integrating Better Auth - the comprehensive TypeScript authentication framework.
---

# Better Auth Integration Guide

**Always consult [better-auth.com/docs](https://better-auth.com/docs) for code examples and latest API.**

Better Auth is a TypeScript-first, framework-agnostic auth framework supporting email/password, OAuth, magic links, passkeys, and more via plugins.

---

## Quick Reference

### Environment Variables

- `BETTER_AUTH_SECRET` - Encryption secret (min 32 chars). Generate: `openssl rand -base64 32`
- `BETTER_AUTH_URL` - Base URL (e.g., `https://example.com`)

Only define `baseURL`/`secret` in config if env vars are NOT set.

### File Location

CLI looks for `auth.ts` in: `./`, `./lib`, `./utils`, or under `./src`. Use `--config` for custom path.

### CLI Commands

- `npx @better-auth/cli@latest migrate` - Apply schema (built-in adapter)
- `npx @better-auth/cli@latest generate` - Generate schema for Prisma/Drizzle
- `npx @better-auth/cli mcp --cursor` - Add MCP to AI tools

**Re-run after adding/changing plugins.**

---

## Core Config Options

| Option             | Notes                                          |
| ------------------ | ---------------------------------------------- |
| `appName`          | Optional display name                          |
| `baseURL`          | Only if `BETTER_AUTH_URL` not set              |
| `basePath`         | Default `/api/auth`. Set `/` for root.         |
| `secret`           | Only if `BETTER_AUTH_SECRET` not set           |
| `database`         | Required for most features. See adapters docs. |
| `secondaryStorage` | Redis/KV for sessions & rate limits            |
| `emailAndPassword` | `{ enabled: true }` to activate                |
| `socialProviders`  | `{ google: { clientId, clientSecret }, ... }`  |
| `plugins`          | Array of plugins                               |
| `trustedOrigins`   | CSRF whitelist                                 |

---

## Database

**Direct connections:** Pass `pg.Pool`, `mysql2` pool, `better-sqlite3`, or `bun:sqlite` instance.

**ORM adapters:** Import from `better-auth/adapters/drizzle`, `better-auth/adapters/prisma`, `better-auth/adapters/mongodb`.

**Critical:** Better Auth uses adapter model names, NOT underlying table names. If Prisma model is `User` mapping to table `users`, use `modelName: "user"` (Prisma reference), not `"users"`.

---

## Session Management

**Storage priority:**

1. If `secondaryStorage` defined → sessions go there (not DB)
2. Set `session.storeSessionInDatabase: true` to also persist to DB
3. No database + `cookieCache` → fully stateless mode

**Cookie cache strategies:**

- `compact` (default) - Base64url + HMAC. Smallest.
- `jwt` - Standard JWT. Readable but signed.
- `jwe` - Encrypted. Maximum security.

**Key options:** `session.expiresIn` (default 7 days), `session.updateAge` (refresh interval), `session.cookieCache.maxAge`, `session.cookieCache.version` (change to invalidate all sessions).

---

## User & Account Config

**User:** `user.modelName`, `user.fields` (column mapping), `user.additionalFields`, `user.changeEmail.enabled` (disabled by default), `user.deleteUser.enabled` (disabled by default).

**Account:** `account.modelName`, `account.accountLinking.enabled`, `account.storeAccountCookie` (for stateless OAuth).

**Required for registration:** `email` and `name` fields.

---

## Email Flows

- `emailVerification.sendVerificationEmail` - Must be defined for verification to work
- `emailVerification.sendOnSignUp` / `sendOnSignIn` - Auto-send triggers
- `emailAndPassword.sendResetPassword` - Password reset email handler

---

## Security

**In `advanced`:**

- `useSecureCookies` - Force HTTPS cookies
- `disableCSRFCheck` - ⚠️ Security risk
- `disableOriginCheck` - ⚠️ Security risk
- `crossSubDomainCookies.enabled` - Share cookies across subdomains
- `ipAddress.ipAddressHeaders` - Custom IP headers for proxies
- `database.generateId` - Custom ID generation or `"serial"`/`"uuid"`/`false`

**Rate limiting:** `rateLimit.enabled`, `rateLimit.window`, `rateLimit.max`, `rateLimit.storage` ("memory" | "database" | "secondary-storage").

---

## Hooks

**Endpoint hooks:** `hooks.before` / `hooks.after` - Array of `{ matcher, handler }`. Use `createAuthMiddleware`. Access `ctx.path`, `ctx.context.returned` (after), `ctx.context.session`.

**Database hooks:** `databaseHooks.user.create.before/after`, same for `session`, `account`. Useful for adding default values or post-creation actions.

**Hook context (`ctx.context`):** `session`, `secret`, `authCookies`, `password.hash()`/`verify()`, `adapter`, `internalAdapter`, `generateId()`, `tables`, `baseURL`.

---

## Plugins

**Import from dedicated paths for tree-shaking:**

```
import { twoFactor } from "better-auth/plugins/two-factor"
```

NOT `from "better-auth/plugins"`.

**Popular plugins:** `twoFactor`, `organization`, `passkey`, `magicLink`, `emailOtp`, `username`, `phoneNumber`, `admin`, `apiKey`, `bearer`, `jwt`, `multiSession`, `sso`, `oauthProvider`, `oidcProvider`, `openAPI`, `genericOAuth`.

Client plugins go in `createAuthClient({ plugins: [...] })`.

---

## Client

Import from: `better-auth/client` (vanilla), `better-auth/react`, `better-auth/vue`, `better-auth/svelte`, `better-auth/solid`.

Key methods: `signUp.email()`, `signIn.email()`, `signIn.social()`, `signOut()`, `useSession()`, `getSession()`, `revokeSession()`, `revokeSessions()`.

---

## Type Safety

Infer types: `typeof auth.$Infer.Session`, `typeof auth.$Infer.Session.user`.

For separate client/server projects: `createAuthClient<typeof auth>()`.

---

## Common Gotchas

1. **Model vs table name** - Config uses ORM model name, not DB table name
2. **Plugin schema** - Re-run CLI after adding plugins
3. **Secondary storage** - Sessions go there by default, not DB
4. **Cookie cache** - Custom session fields NOT cached, always re-fetched
5. **Stateless mode** - No DB = session in cookie only, logout on cache expiry
6. **Change email flow** - Sends to current email first, then new email

---

## Resources

- [Docs](https://better-auth.com/docs)
- [Options Reference](https://better-auth.com/docs/reference/options)
- [LLMs.txt](https://better-auth.com/llms.txt)
- [GitHub](https://github.com/better-auth/better-auth)
- [Init Options Source](https://github.com/better-auth/better-auth/blob/main/packages/core/src/types/init-options.ts)

Overview

This skill integrates Better Auth, a TypeScript-first, framework-agnostic authentication framework, into full-stack web AI apps. It provides production-ready patterns, configuration guidance, and recipes for email/password, OAuth, magic links, passkeys, and plugin-driven features. The goal is a repeatable, secure auth integration that works with Prisma, Drizzle, direct DB pools, or secondary storage like Redis.

How this skill works

The skill inspects and generates the core auth configuration (auth.ts) and guides CLI usage to generate or migrate schema. It validates environment variables, database adapter selections, session and cookie cache strategies, and plugin wiring. It also outlines hooks, email flows, and common security options so you can implement sessions, account linking, and advanced features consistently.

When to use it

  • Adding authentication to a TypeScript full-stack app (Next, Remix, Solid, Svelte, Vue, etc.).
  • Migrating or standardizing auth across multiple services or monorepos.
  • Implementing multi-provider logins: email/password, OAuth, magic links, passkeys.
  • Setting up secure session storage with Redis/secondary storage or cookie strategies.
  • Integrating Better Auth plugins like two-factor, organization, or passkey.

Best practices

  • Always set BETTER_AUTH_SECRET and BETTER_AUTH_URL in production environment variables.
  • Use adapter modelName (ORM model) rather than raw table names to avoid mapping errors.
  • Store sessions in secondaryStorage (Redis) and enable DB persistence only when needed.
  • Re-run the Better Auth CLI after adding or changing plugins so schema stays in sync.
  • Prefer secure cookie settings (useSecureCookies, proper sameSite) and enable rate limiting.

Example use cases

  • Create an auth.ts config for Prisma with Google OAuth and email/password, plus session in Redis.
  • Add two-factor and passkey plugins for high-security admin workflows.
  • Enable stateless cookieCache compact mode for serverless deployments with no DB.
  • Hook before-user-create to populate tenant defaults and after-user-create to send welcome emails.
  • Generate migration and schema files with the CLI, then run migrate to apply adapter changes.

FAQ

What env vars are required?

At minimum set BETTER_AUTH_SECRET (min 32 chars) and BETTER_AUTH_URL in production. You can omit secrets/baseURL in config if env vars exist.

How do sessions behave with secondaryStorage?

If secondaryStorage is defined, sessions live there by default. You can also enable session.storeSessionInDatabase to persist sessions in the DB as well.