Better Auth: Integration GuideSkill

---
name: better-auth-best-practices
description: Configure Better Auth server and client, set up database adapters, manage sessions, add plugins, and handle environment variables. Use when users mention Better Auth, betterauth, auth.ts, or need to set up TypeScript authentication with email/password, OAuth, or plugin configuration.
---

# Better Auth Integration Guide

## Documentation Version

Use documentation that matches the Better Auth version installed in the project. APIs and plugin names can differ across maintained release lines.

1. Prefer a version explicitly named by the user.
2. Otherwise, inspect the resolved `better-auth` version in the lockfile, falling back to the package manifest when no lockfile is available.
3. When the Better Auth MCP is available, call `get_doc` with `/llms.txt` to resolve that package version to a documentation identifier. Pass the identifier to every `search_docs` call and pass result paths to `get_doc` unchanged.
4. Without MCP, start at [better-auth.com/llms.txt](https://better-auth.com/llms.txt) and follow the matching version index.
5. Use the latest documentation only when the project version cannot be determined or the user explicitly asks about the latest release or an upgrade.

When planning an upgrade, separate guidance for the currently installed version from guidance for the target version.

---

## Setup Workflow

1. Install: `npm install better-auth`
2. Set env vars: `BETTER_AUTH_SECRET` and `BETTER_AUTH_URL`
3. Create `auth.ts` with database + config
4. Create route handler for your framework
5. Run migrations:
   - **Built-in adapter:** `npx auth@latest migrate`
   - **Drizzle:** `npx auth@latest generate --output src/db/auth-schema.ts` then `npx drizzle-kit push` (dev) or `npx drizzle-kit generate && npx drizzle-kit migrate` (prod)
   - **Prisma:** `npx auth@latest generate --output prisma/schema.prisma` then `npx prisma migrate dev`
6. Verify: call `GET /api/auth/ok` — should return `{ status: "ok" }`

---

## 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 auth@latest migrate` - Apply schema (built-in adapter)
- `npx auth@latest generate` - Generate schema for Prisma/Drizzle
- `npx auth@latest 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. For Postgres, also supports `postgres` (postgres.js) and `@neondatabase/serverless`.

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

**Drizzle provider values:** `"pg"` (PostgreSQL), `"mysql"` (MySQL), `"sqlite"` (SQLite). Must match the driver used.

**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
7. **Drizzle: db not initialized** - `drizzleAdapter(db, ...)` requires a `db` instance from `drizzle()`. See `create-auth` skill for setup examples (node-postgres, postgres.js, Neon).
8. **Drizzle: missing drizzle.config.ts** - `drizzle-kit` commands require a `drizzle.config.ts` pointing to the generated schema file and DB credentials.

---

## 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)