What is auth-handler?

A guide for adding Better Auth login and user-session handling to an application, including protecting API routes and reading user data.

Use it for sign-up and login flows, protecting API endpoints, checking sessions, and fetching current user information.

It helps prevent unprotected server routes and keeps client-side and server-side authentication checks consistent.

auth-handler — Skill for Claude Code by Indie-Kit/nextjs-saas-starter

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 Indie-Kit/nextjs-saas-starter --skill auth-handler

Clone the repo

git clone --depth 1 https://github.com/Indie-Kit/nextjs-saas-starter

Made for: Claude Code.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/indie-kit/nextjs-saas-starter/auth-handler/github.svg)](https://agentmods.dev/skills/indie-kit/nextjs-saas-starter/auth-handler)

Your own site

<a href="https://agentmods.dev/skills/indie-kit/nextjs-saas-starter/auth-handler"><img src="https://agentmods.dev/badge/skills/indie-kit/nextjs-saas-starter/auth-handler/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/indie-kit/nextjs-saas-starter/auth-handler"><img src="https://agentmods.dev/badge/skills/indie-kit/nextjs-saas-starter/auth-handler.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 28 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 312 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.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00028	$0.00312
Opus 5.5	$0.00011	$0.00125
Sonnet 5.5	$0.00006	$0.00062
Haiku 4.5	$0.00003	$0.00031

Measured 1mo ago against content hash 21a965cecd1e, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

auth-handler 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 1mo 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/auth-handler/SKILL.md · 38 lines

What it actually says

Auth Handler

Instructions

1. API Route Protection

User Routes: Use withAuthRequired.

import { withAuthRequired } from "@/lib/auth/withAuthRequired";

export const GET = withAuthRequired(async (req, { session, user, getDbUser }) => {
   // getDbUser() is available to fetch fresh user data from DB if needed
   const dbUser = await getDbUser();
});

Defense in Depth: Do NOT rely solely on middleware. Always implement individual route protection using withAuthRequired.

2. Frontend Data Access

Client-Side: Use useSession from src/lib/auth-client.ts.

import { useSession } from "@/lib/auth-client";
const { data: session } = useSession();

Do NOT use NextAuth imports. Use @/lib/auth-client.

3. Server-Side Data Access

Check Auth: Import auth from @/lib/auth.
Get Context: Use auth.api.getSession({ headers: await headers() }).

Reference

For architecture details, see reference.md.

Files

What ships with it

1 file 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.

reference.md 900 B

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.

1mo ago First seen · 38 lines · 28 tokens per session scan A 21a965cecd1e

Subscribe to this mod's changes

auth-handler is a skill published in the GitHub repository Indie-Kit/nextjs-saas-starter (28 stars, last pushed 20d ago), licensed MIT. It adds 28 tokens to every session and 312 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 2026-08-30.

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