Auth.js v5 Authentication Stack Agent Skill

Production-ready Auth.js v5 setup for Next.js and Cloudflare Workers.

Context cost
18.5k tokensestimated from the bundle, loaded when it triggers
Bundle
3 files · 73.9 kBtext throughout, nothing executable
Licence
MITthe author’s own terms
Last change
—v1.0.0
Servers it uses
Noneruns standalone

What it does

Production-ready Auth.js v5 setup for Next.js and Cloudflare Workers. Use when: setting up authentication, implementing OAuth/credentials/magic links, configuring D1 or PostgreSQL adapters, debugging session issues, migrating from v4 to v5, fixing edge compatibility, troubleshooting JWT/database sessions, resolving AUTH_SECRET errors, fixing CallbackRouteError, or implementing RBAC.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

cloudflarenextjssecuritytesting

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md30.3 kB · preview
--- name: auth-js license: MIT metadata: version: 1.0.0 last_updated: 2025-10-26 package_versions: next-auth: 4.24.11 "@auth/core": 0.41.1 "@auth/d1-adapter": 1.11.1 production_tested: true token_savings: ~60% errors_prevented: 12 ---
33# Auth.js v5 Authentication Stack
34
35**Production-tested**: Multiple Next.js and Cloudflare Workers projects
36**Last Updated**: 2025-10-26
37**Status**: Production Ready ✅
38**Official Docs**: https://authjs.dev
39
40---
41
42## ⚠️ BEFORE YOU START (READ THIS!)
43
44**CRITICAL FOR AI AGENTS**: If you're Claude Code helping a user set up Auth.js:
45
461. **Explicitly state you're using this skill** at the start of the conversation
472. **Reference patterns from the skill** rather than general knowledge
483. **Prevent known issues** listed in references/common-errors.md
494. **Don't guess** - if unsure, check the skill documentation
50
51**USER ACTION REQUIRED**: Tell Claude to check this skill first!
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md3,634 words
Files3
LicenceMIT
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈320
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
18,155
on trigger
The instruction body and 2 supporting files, read only when the skill fires.
9.2%
of a 200k window
Ten skills this size would take about 92% of the window before you open a file.
050k100k150k200k context window

18.5k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Heavy. Teams tend to install this one per project rather than globally, and load it only when the job comes up.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md does not declare which tools it asks the agent for, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

This SKILL.md carries no allowed-tools line, so neither is declared. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

3 files, 73.9 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in. 1 file of its source is not in the download — listed after these, with why.

  • SKILL.md30.3 kB
  • README.md10.7 kB
  • SKILL.json32.9 kB

Not in the download

Not carried is a type a skill download does not hold. Take it from its source.

  • SKILL.md.backupnot carried
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the download is 3 files — not the whole of its source: 1 file is left out. It is listed under the files, with why. The MIT licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# Auth.js v5 Authentication Stack · 18.5k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/auth-js-v5-authentication-stack/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/auth-js-v5-authentication-stack" ] && { [ ! -e .claude/skills/auth-js-v5-authentication-stack ] || { mv .claude/skills/auth-js-v5-authentication-stack "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/auth-js-v5-authentication-stack" .claude/skills/ && echo "Installed .claude/skills/auth-js-v5-authentication-stack"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add davidanthonyn/auth-js-v5-authentication-stack

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/auth-js-v5-authentication-stack/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/auth-js-v5-authentication-stack/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/auth-js-v5-authentication-stack" ] && { [ ! -e ~/.claude/skills/auth-js-v5-authentication-stack ] || { mv ~/.claude/skills/auth-js-v5-authentication-stack "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/auth-js-v5-authentication-stack" ~/.claude/skills/ && echo "Installed ~/.claude/skills/auth-js-v5-authentication-stack" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/auth-js-v5-authentication-stack/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where. It appears as auth-js in Gemini CLI, Codex, Copilot and Grok (its own name); Claude Code lists it by the folder name, auth-js-v5-authentication-stack. Not in this download: 1 file of its source (which one, and why). Take it from its source.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Version1.0.0
Publishedno release date on file
PriceFree
Referencedavidanthonyn/auth-js-v5-authentication-stack

Versions

v1.0.0 is what is on the shelf; no release here carries a date. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

v1.0.0
  • No earlier releases have been published to the marketplace.
Pinning

The install command always fetches the release that is current the day you run it — v1.0.0 today — and cannot ask for an earlier one. The copy on your disk does not change until you run it again.

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