create-auth-skill

create-auth-skill is a skill for Claude Code, Codex from charlietlamb/ferix. It costs 21 tokens per session (1,713 once invoked), scanned A, original, MIT.

A setup guide for adding user sign-in and account access to TypeScript or JavaScript apps with Better Auth, a framework for authentication. It covers new projects, existing authentication, database setup, route handlers, and schema changes.

In plain words
What is it for?
Use it to add Better Auth to a new or existing app, configure its database, run schema migrations, and connect authentication to existing pages. It also points to optional packages for features such as passkeys, enterprise single sign-on, payments, and SCIM.
Why use it?
It gives a clear path through the setup work and helps identify gaps when adding or replacing authentication. This reduces the chance of missing required files, routes, or database changes.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/charlietlamb/ferix/create-auth-skill
Any agent
npx skills add charlietlamb/ferix --skill create-auth-skill
Clone the repo
git clone --depth 1 https://github.com/charlietlamb/ferix

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for create-auth-skill

README.md
[![agentmods](https://agentmods.dev/badge/skills/charlietlamb/ferix/create-auth-skill.svg)](https://agentmods.dev/skills/charlietlamb/ferix/create-auth-skill)
Your own site
<a href="https://agentmods.dev/skills/charlietlamb/ferix/create-auth-skill"><img src="https://agentmods.dev/badge/skills/charlietlamb/ferix/create-auth-skill.svg" alt="Measured on agentmods" height="20"></a>
Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,713 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00021 $0.01713
Opus 5 $0.00010 $0.00856
Sonnet 5 $0.00004 $0.00343
Haiku 4.5 $0.00002 $0.00171

Measured 5d ago against content hash 7334700b51f3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

create-auth-skill scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/create-auth-skill/SKILL.md · 214 lines

How it starts

The opening of the file, as written. The whole thing — 214 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Create Auth Skill

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

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


Decision Tree

Is this a new/empty project?
├─ YES → New project setup
│   1. Identify framework
│   2. Choose database
│   3. Install better-auth
│   4. Create auth.ts + auth-client.ts
│   5. Set up route handler
│   6. Run CLI migrate/generate
│   7. Add features via plugins
│
└─ NO → Does project have existing auth?
    ├─ YES → Migration/enhancement
    │   • Audit current auth for gaps
    │   • Plan incremental migration
    │   • See migration guides in docs
    │
    └─ NO → Add auth to existing project
        1. Analyze project structure
        2. Install better-auth
        3. Create auth config
        4. Add route handler
        5. Run schema migrations
        6. Integrate into existing pages

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

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 or 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

Read the full file on GitHub · 214 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 5d ago First seen · 214 lines · 21 tokens per session scan A 7334700b51f3

Subscribe to this mod's changes

create-auth-skill is a skill published in the GitHub repository charlietlamb/ferix (10 stars, last pushed 6mo ago), licensed MIT. It adds 21 tokens to every session and 1,713 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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