Create Auth Skill

Guide for adding authentication to TypeScript/JavaScript applications using Better Auth.

For code examples and syntax, see better-auth.com/docs.

Phase 1: Planning (REQUIRED before implementation)

Before writing any code, gather requirements by scanning the project and asking the user structured questions. This ensures the implementation matches their needs.

Step 1: Scan the project

Analyze the codebase to auto-detect:

Framework — Look for

next.config

svelte.config

nuxt.config

astro.config

vite.config

, or Express/Hono entry files.

Database/ORM — Look for

prisma/schema.prisma

drizzle.config

package.json

deps (

pg

mysql2

better-sqlite3

mongoose

mongodb

Existing auth — Look for existing auth libraries (
```
next-auth
```
,
```
lucia
```
,
```
clerk
```
,
```
supabase/auth
```
,
```
firebase/auth
```
) in
```
package.json
```
or imports.

Package manager — Check for

pnpm-lock.yaml

yarn.lock

bun.lockb

, or

package-lock.json

Use what you find to pre-fill defaults and skip questions you can already answer.

Step 2: Ask planning questions

Use the

AskQuestion

tool to ask the user all applicable questions in a single call. Skip any question you already have a confident answer for from the scan. Group them under a title like "Auth Setup Planning".

Questions to ask:

Project type (skip if detected)
- Prompt: "What type of project is this?"
- Options: New project from scratch | Adding auth to existing project | Migrating from another auth library
Framework (skip if detected)
- Prompt: "Which framework are you using?"
- Options: Next.js (App Router) | Next.js (Pages Router) | SvelteKit | Nuxt | Astro | Express | Hono | SolidStart | Other
Database & ORM (skip if detected)
- Prompt: "Which database setup will you use?"
- Options: PostgreSQL (Prisma) | PostgreSQL (Drizzle) | PostgreSQL (pg driver) | MySQL (Prisma) | MySQL (Drizzle) | MySQL (mysql2 driver) | SQLite (Prisma) | SQLite (Drizzle) | SQLite (better-sqlite3 driver) | MongoDB (Mongoose) | MongoDB (native driver)
Authentication methods (always ask, allow multiple)
- Prompt: "Which sign-in methods do you need?"
- Options: Email & password | Social OAuth (Google, GitHub, etc.) | Magic link (passwordless email) | Passkey (WebAuthn) | Phone number
- ```
allow_multiple: true
```
Social providers (only if they selected Social OAuth above — ask in a follow-up call)
- Prompt: "Which social providers do you need?"
- Options: Google | GitHub | Apple | Microsoft | Discord | Twitter/X
- ```
allow_multiple: true
```
Email verification (only if Email & password was selected above — ask in a follow-up call)
- Prompt: "Do you want to require email verification?"
- Options: Yes | No
Email provider (only if email verification is Yes, or if Password reset is selected in features — ask in a follow-up call)
- Prompt: "How do you want to send emails?"
- Options: Resend | Mock it for now (console.log)
Features & plugins (always ask, allow multiple)
- Prompt: "Which additional features do you need?"
- Options: Two-factor authentication (2FA) | Organizations / teams | Admin dashboard | API bearer tokens | Password reset | None of these
- ```
allow_multiple: true
```
Auth pages (always ask, allow multiple — pre-select based on earlier answers)
- Prompt: "Which auth pages do you need?"
- Options vary based on previous answers:
  - Always available: Sign in | Sign up
  - If Email & password selected: Forgot password | Reset password
  - If email verification enabled: Email verification
- ```
allow_multiple: true
```
Auth UI style (always ask)

Prompt: "What style do you want for the auth pages? Pick one or describe your own."
Options: Minimal & clean | Centered card with background | Split layout (form + hero image) | Floating / glassmorphism | Other (I'll describe)

Step 3: Summarize the plan

After collecting answers, present a concise implementation plan as a markdown checklist. Example:

## Auth Implementation Plan

- **Framework:** Next.js (App Router)
- **Database:** PostgreSQL via Prisma
- **Auth methods:** Email/password, Google OAuth, GitHub OAuth
- **Plugins:** 2FA, Organizations, Email verification
- **UI:** Custom forms

### Steps
1. Install `better-auth` and `@better-auth/cli`
2. Create `lib/auth.ts` with server config
3. Create `lib/auth-client.ts` with React client
4. Set up route handler at `app/api/auth/[...all]/route.ts`
5. Configure Prisma adapter and generate schema
6. Add Google & GitHub OAuth providers
7. Enable `twoFactor` and `organization` plugins
8. Set up email verification handler
9. Run migrations
10. Create sign-in / sign-up pages

Ask the user to confirm the plan before proceeding to Phase 2.

Phase 2: Implementation

Only proceed here after the user confirms the plan from Phase 1.

Follow the decision tree below, guided by the answers collected above.

Is this a new/empty project?
├─ YES → New project setup
│   1. Install better-auth (+ scoped packages per plan)
│   2. Create auth.ts with all planned config
│   3. Create auth-client.ts with framework client
│   4. Set up route handler
│   5. Set up environment variables
│   6. Run CLI migrate/generate
│   7. Add plugins from plan
│   8. Create auth UI pages
│
├─ MIGRATING → Migration from existing auth
│   1. Audit current auth for gaps
│   2. Plan incremental migration
│   3. Install better-auth alongside existing auth
│   4. Migrate routes, then session logic, then UI
│   5. Remove old auth library
│   6. See migration guides in docs
│
└─ ADDING → Add auth to existing project
    1. Analyze project structure
    2. Install better-auth
    3. Create auth config matching plan
    4. Add route handler
    5. Run schema migrations
    6. Integrate into existing pages
    7. Add planned plugins and features

At the end of implementation, guide users thoroughly on remaining next steps (e.g., setting up OAuth app credentials, deploying env vars, testing flows).

Installation

Core:

npm install better-auth

Scoped packages (as needed):

Package	Use case
`@better-auth/passkey`	WebAuthn/Passkey auth
`@better-auth/sso`	SAML/OIDC enterprise SSO
`@better-auth/stripe`	Stripe payments
`@better-auth/scim`	SCIM user provisioning
`@better-auth/expo`	React Native/Expo

Environment Variables

env

BETTER_AUTH_SECRET=<32+ chars, generate with: openssl rand -base64 32>
BETTER_AUTH_URL=http://localhost:3000
DATABASE_URL=<your database connection string>

Add OAuth secrets as needed:

GITHUB_CLIENT_ID

GITHUB_CLIENT_SECRET

GOOGLE_CLIENT_ID

, etc.

Server Config (auth.ts)

Location:

lib/auth.ts

src/lib/auth.ts

Minimal config needs:

```
database
```
- Connection or adapter
```
emailAndPassword: { enabled: true }
```
- For email/password auth

Standard config adds:

```
socialProviders
```
- OAuth providers (google, github, etc.)
```
emailVerification.sendVerificationEmail
```
- Email verification handler
```
emailAndPassword.sendResetPassword
```
- Password reset handler

Full config adds:

```
plugins
```
- Array of feature plugins
```
session
```
- Expiry, cookie cache settings
```
account.accountLinking
```
- Multi-provider linking
```
rateLimit
```
- Rate limiting config

Export types:

export type Session = typeof auth.$Infer.Session

Client Config (auth-client.ts)

Import by framework:

Framework	Import
React/Next.js	`better-auth/react`
Vue	`better-auth/vue`
Svelte	`better-auth/svelte`
Solid	`better-auth/solid`
Vanilla JS	`better-auth/client`

Client plugins go in

createAuthClient({ plugins: [...] })

Common exports:

signIn

signUp

signOut

useSession

getSession

Route Handler Setup

Framework	File	Handler
Next.js App Router	`app/api/auth/[...all]/route.ts`	`toNextJsHandler(auth)` → export `{ GET, POST }`
Next.js Pages	`pages/api/auth/[...all].ts`	`toNextJsHandler(auth)` → default export
Express	Any file	`app.all("/api/auth/*", toNodeHandler(auth))`
SvelteKit	`src/hooks.server.ts`	`svelteKitHandler(auth)`
SolidStart	Route file	`solidStartHandler(auth)`
Hono	Route file	`auth.handler(c.req.raw)`

Next.js Server Components: Add

nextCookies()

plugin to auth config.

Database Migrations

Adapter Command

Built-in Kysely

Adapter	Command
Built-in Kysely	`npx @better-auth/cli@latest migrate` (applies directly)
Prisma	`npx @better-auth/cli@latest generate --output prisma/schema.prisma` then `npx prisma migrate dev`
Drizzle	`npx @better-auth/cli@latest generate --output src/db/auth-schema.ts` then `npx drizzle-kit push`

npx @better-auth/cli@latest migrate

(applies directly)

Prisma

npx @better-auth/cli@latest generate --output prisma/schema.prisma

then

npx prisma migrate dev

Drizzle

npx @better-auth/cli@latest generate --output src/db/auth-schema.ts

then

npx drizzle-kit push

Re-run after adding plugins.

Database Adapters

Database	Setup
SQLite	Pass `better-sqlite3` or `bun:sqlite` instance directly
PostgreSQL	Pass `pg.Pool` instance directly
MySQL	Pass `mysql2` pool directly
Prisma	`prismaAdapter(prisma, { provider: "postgresql" })` from `better-auth/adapters/prisma`
Drizzle	`drizzleAdapter(db, { provider: "pg" })` from `better-auth/adapters/drizzle`
MongoDB	`mongodbAdapter(db)` from `better-auth/adapters/mongodb`

Common Plugins

Plugin	Server Import	Client Import	Purpose
`twoFactor`	`better-auth/plugins`	`twoFactorClient`	2FA with TOTP/OTP
`organization`	`better-auth/plugins`	`organizationClient`	Teams/orgs
`admin`	`better-auth/plugins`	`adminClient`	User management
`bearer`	`better-auth/plugins`	-	API token auth
`openAPI`	`better-auth/plugins`	-	API docs
`passkey`	`@better-auth/passkey`	`passkeyClient`	WebAuthn
`sso`	`@better-auth/sso`	-	Enterprise SSO

Plugin pattern: Server plugin + client plugin + run migrations.

Auth UI Implementation

Sign in flow:

signIn.email({ email, password })

signIn.social({ provider, callbackURL })

Handle
```
error
```
in response
Redirect on success

Session check (client):

useSession()

hook returns

{ data: session, isPending }

Session check (server):

auth.api.getSession({ headers: await headers() })

Protected routes: Check session, redirect to

/sign-in

if null.

Security Checklist

```
BETTER_AUTH_SECRET
```
set (32+ chars)
```
advanced.useSecureCookies: true
```
in production
```
trustedOrigins
```
configured
Rate limits enabled
Email verification enabled
Password reset implemented
2FA for sensitive apps
CSRF protection NOT disabled
```
account.accountLinking
```
reviewed

Troubleshooting

Issue	Fix
"Secret not set"	Add `BETTER_AUTH_SECRET` env var
"Invalid Origin"	Add domain to `trustedOrigins`
Cookies not setting	Check `baseURL` matches domain; enable secure cookies in prod
OAuth callback errors	Verify redirect URIs in provider dashboard
Type errors after adding plugin	Re-run CLI generate/migrate

create-auth-skill

NPX Install

Tags

SKILL.md Content