JackSmack1971/.agents/skills/better-auth/better-auth-best-practices

description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

Summary

• Covers full workflow from installation through database migration, environment variable setup, and route handler creation across multiple frameworks
• Supports multiple database adapters (Prisma, Drizzle, MongoDB, direct connections) with critical guidance on model vs. table naming conventions
• Includes session storage strategies with secondary storage (Redis/KV), cookie caching modes (compact, JWT, JWE), and stateless operation options
• Provides 10+ popular plugins (two-factor, organization, passkey, magic link, OAuth provider, SSO) with tree-shaking imports and client-side integration
• Features before/after hooks at endpoint and database levels, rate limiting configuration, CSRF/origin security controls, and type-safe client methods across vanilla, React, Vue, Svelte, and Solid frameworks

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description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

SKILL.md

Better Auth Integration Guide

Always consult better-auth.com/docs for code examples and latest API.

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description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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 npx @better-auth/cli@latest migrate
6. Verify: call GET /api/auth/ok — should return { status: "ok" }

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description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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.

---

description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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 |

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description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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".

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description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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).

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description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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.

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description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

Email Flows

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

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description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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").

---

description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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.

---

description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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: [...] }).

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description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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().

---

description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

Type Safety

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

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

---

description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

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

---

description: Implements Better Auth patterns for Next.js, session handling, and OAuth flows.

Resources

• Docs
• Options Reference
• LLMs.txt
• GitHub
• Init Options Source