better-auth-scaffold

name

better-auth-scaffold

description

Scaffolds a Better Auth setup in a Next.js (App Router) + Drizzle project — lib/auth.ts, lib/auth-client.ts, the /api/auth/[...all] route handler, middleware.ts, .env.example, and a permissions module. Produces convention-enforced templates for three plugin presets (minimal, social, advanced with twoFactor+magicLink). Trigger even when the user doesn't explicitly say "scaffold" — phrases like "set up Better Auth", "wire up auth", "initialize auth in this project", or "add auth to Next.js" should pull this in. Pairs with the `better-auth` skill, which covers the rules these templates encode.

Better Auth Scaffold (Next.js + Drizzle)

Parameterized templates for bootstrapping a Better Auth setup in a Next.js App Router project using the Drizzle adapter. Each template enforces the conventions documented in references/conventions.md — file layout, plugin ordering, env handling, runtime selection.

When to Apply

Reference these templates when:

• Starting a new Next.js project that needs authentication
• Adding Better Auth to an existing Next.js + Drizzle codebase
• Refactoring a partial Better Auth setup that's missing the catch-all route, middleware, or nextCookies() ordering
• Generating a per-feature variant (minimal, social, advanced) on top of an existing project

Setup

Required parameters

Parameter	Required	Default	Description
preset	no	minimal	minimal (email+password) | social (adds Google + GitHub) | advanced (social + twoFactor + magicLink)
db_provider	yes	—	pg | mysql | sqlite (Drizzle provider)
app_name	yes	—	Display name (becomes 2FA issuer in authenticator apps when preset=advanced)

Optional parameters

Parameter	Default	Description
auth_path	lib/auth.ts	Server auth module path
client_path	lib/auth-client.ts	Client module path
api_route_path	app/api/auth/[...all]/route.ts	Catch-all route handler path
protected_paths	["/dashboard"]	Routes the middleware guards

If config.json already exists with values, the skill uses those; otherwise it asks the user.

Available Templates

Template	Output File	When to emit
auth.ts.template	lib/auth.ts	Always
auth-client.ts.template	lib/auth-client.ts	Always
route.ts.template	app/api/auth/[...all]/route.ts	Always
middleware.ts.template	middleware.ts	When protected_paths is non-empty
env.template	.env.example	Always
db-schema-better-auth.ts.template	db/schema/auth.ts	Always (stub — replace with output of better-auth generate)
db-index.ts.template	db/index.ts	When the project has no Drizzle client yet
email.ts.template	lib/email.ts	When preset=advanced (and the file doesn't already exist)
sign-in-page.tsx.template	app/sign-in/page.tsx	When the project has no sign-in page (closes the middleware redirect loop)
permissions.ts.template	lib/permissions.ts	Optional starter for org/admin plugin work

How to Use

1. Resolve parameters. Read config.json first; for any missing required parameter (db_provider, app_name), ask the user via AskUserQuestion.

2. Render each template. For each template file:

   • Read the template.
   • Substitute {{placeholder}} values ({{app_name}}, {{db_provider}}, etc.) with the resolved parameter values.
   • Apply PRESET[...] conditional blocks using these rules:
     1. Find every pair of marker lines matching // PRESET[<tags>] and // /PRESET[<tags>] (or /* PRESET[...] */ / # PRESET[...] for non-JS files — same syntax, different comment style).
     2. Parse <tags> as a comma-separated list (e.g. social,advanced).
     3. If the chosen preset value is in <tags> → remove ONLY the two marker lines; keep the lines between them.
     4. If the chosen preset value is NOT in <tags> → remove the ENTIRE block including both marker lines.
     5. Markers may be nested (e.g. PRESET[advanced] inside PRESET[minimal,social,advanced]); process from inside out.
   • For Mustache-style iteration in middleware.ts.template (// {{#protected_paths}} ... // {{/protected_paths}}), repeat the lines between the markers once per item in the list, substituting {{path}} with each value.

3. Write output files. Before writing, check if the target file already exists:

   • If it doesn't exist → write it.
   • If it exists and is identical → no-op.
   • If it exists and differs → show a diff and ask the user (overwrite / merge / skip).

4. Run the CLI sequence. After all files are written:

   npx @better-auth/cli@latest generate
   npx drizzle-kit generate
   npx drizzle-kit migrate
   

   These commands replace the placeholder db/schema/auth.ts with the real schema and apply migrations.

5. Print next steps. Tell the user to:

   • Fill in .env.local (copy from .env.example)
   • Generate a secret: openssl rand -base64 32
   • Register OAuth redirect URIs with each provider console (for social/advanced presets)
   • Implement lib/email.ts to wire transactional email (for advanced preset)

Conventions

Read references/conventions.md for the rationale behind every convention these templates encode. Highlights:

• lib/auth.ts is server-only (import "server-only")
• nextCookies() is ALWAYS the last plugin in the array
• Middleware does a cookie-presence check only; real validation in pages
• All secrets via process.env.*, never inline
• Sliding-window sessions with cookieCache enabled

Related Skills

• better-auth — Library/API Reference with 42 rules covering setup, sessions, security, plugins, and migration. The templates here are one canonical realization of those rules; read the rule for the underlying reasoning when you need to deviate.

Gotchas

See gotchas.md — initialized empty, populated as we discover them.