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better-auth

better-auth is a skill for Claude Code from fusengine/agents. It costs 32 tokens per session (2,121 once invoked), scanned A, original, MIT.

A guide to adding Better Auth authentication to TypeScript and JavaScript applications, with Next.js-specific setup. Authentication is the process of confirming who a user is and managing their login session.

In plain words
What is it for?
Use it when adding email or social login, two-factor authentication, passkeys, enterprise single sign-on, organizations, API keys, or subscription billing.
Why use it?
It brings login, identity providers, extra sign-in checks, organization accounts, and session handling into one documented approach. It also explains how to connect authentication to databases and billing systems.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter.

Part of the fuse-nextjs plugin — 11 skills, 1 agent shipped together

not rated 32repo +1 changed 21d ago A scan SkillSpector: pass 32 tokens original MIT

Good fit Use it when adding email or social login, two-factor authentication, passkeys, enterprise single sign-on, organizations, API keys, or subscription billing.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/fusengine/agents/better-auth
View source ↗ fusengine/agents
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.

Any agent
npx skills add fusengine/agents --skill better-auth
Clone the repo
git clone --depth 1 https://github.com/fusengine/agents

Made for: Claude Code.

Or install fuse-nextjs, the plugin that ships this one along with the rest of its 11 skills, 1 agent.

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 better-auth

README.md
[![agentmods](https://agentmods.dev/badge/skills/fusengine/agents/better-auth/github.svg)](https://agentmods.dev/skills/fusengine/agents/better-auth)
Your own site
<a href="https://agentmods.dev/skills/fusengine/agents/better-auth"><img src="https://agentmods.dev/badge/skills/fusengine/agents/better-auth/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for better-auth

Your own site · 80×15
<a href="https://agentmods.dev/skills/fusengine/agents/better-auth"><img src="https://agentmods.dev/badge/skills/fusengine/agents/better-auth.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 32 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,121 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 $0.00032 $0.02121
Opus 5.5 $0.00013 $0.00848
Sonnet 5.5 $0.00006 $0.00424
Haiku 4.5 $0.00003 $0.00212

Measured 21d ago against content hash ea0dc3620948, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

better-auth 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 21d 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.

plugins/nextjs-expert/skills/better-auth/SKILL.md · 142 lines

How it starts

The opening of the file, as written. The whole thing — 142 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Covers the full surface — 40+ OAuth providers (Google, GitHub, Discord, Apple, Microsoft, and more), 20+ plugins (2FA, magic links, passkeys, organizations/multi-tenant, enterprise SSO/SAML, SCIM provisioning, Stripe/Polar billing, JWT/Bearer, API keys), and database adapters (Prisma, Drizzle, MongoDB, raw SQL). Also covers migration paths from Auth.js, Clerk, Auth0, Supabase, and WorkOS. While Better Auth itself is framework-agnostic, this skill's architecture guidance (proxy.ts, App Router API route) is Next.js-specific — for Prisma schema/query details see prisma-7.

Better Auth - Complete Authentication

TypeScript-first authentication library with 40+ OAuth providers and 20+ plugins.

Agent Workflow (MANDATORY)

Before ANY implementation, spawn 3 agents in parallel, one Agent call each with a name:

  1. fuse-ai-pilot:explore-codebase - Analyze existing auth setup and patterns
  2. fuse-ai-pilot:research-expert - Verify latest Better Auth docs via Context7/Exa
  3. mcp__context7__query-docs - Check providers/plugins availability

After implementation, run fuse-ai-pilot:sniper for validation.

Overview

When to Use

  • Implementing authentication in TypeScript/JavaScript applications
  • Need OAuth providers (Google, GitHub, Discord, Apple, Microsoft, etc.)
  • Adding 2FA, magic links, passkeys, or phone authentication
  • Enterprise SSO with SAML, SCIM provisioning, or organizations
  • Integrating payments with Stripe or Polar subscriptions
  • Web3 authentication with Sign-In with Ethereum (SIWE)
  • Migrating from Auth.js, Clerk, Auth0, Supabase, or WorkOS

Why Better Auth

Feature Benefit
Framework agnostic Next.js, SvelteKit, Nuxt, Remix, Astro, Expo, NestJS
Plugin architecture Add only the features you need (20+ plugins)
Full TypeScript End-to-end type safety, inference included
Self-hosted Your data stays on your infrastructure
Database flexible Prisma, Drizzle, MongoDB, PostgreSQL, MySQL, SQLite
Enterprise ready SSO, SCIM, organizations, audit logs

Read the full file on GitHub · 142 lines

Files

What ships with it

60 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 21d ago Changed · +10 lines ea0dc3620948
  2. 1mo ago Changed 4a2d62f306d1
  3. 1mo ago First seen · 132 lines · 32 tokens per session scan A 9265eee11fea

Subscribe to this mod's changes

better-auth is a skill published in the GitHub repository fusengine/agents (32 stars, last pushed 7d ago), licensed MIT. It adds 32 tokens to every session and 2,121 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-09-03.

Backend and APIsClaude CodeSecurityclaude-agentclaude-agentsclaude-code-pluginclaude-skillsclaudecode
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