What is atproto-oauth?

A guide to AT Protocol OAuth, the sign-in and permission system used by applications in the AT Protocol network, implemented in Rust, TypeScript, or Go.

Use it to implement, audit, or debug backend, single-page web, and desktop OAuth clients and their authorization, token, and resource requests.

It helps avoid mistakes in a security-sensitive login flow that requires PKCE, PAR, DPoP, published client metadata, and carefully designed permissions.

atproto-oauth — Skill for Claude Code by ngerakines/atproto-skills

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 ngerakines/atproto-skills --skill atproto-oauth

Clone the repo

git clone --depth 1 https://github.com/ngerakines/atproto-skills

Made for: Claude Code.

Or install atproto-skills, the plugin that ships this one along with the rest of its 7 skills.

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/ngerakines/atproto-skills/atproto-oauth/github.svg)](https://agentmods.dev/skills/ngerakines/atproto-skills/atproto-oauth)

Your own site

<a href="https://agentmods.dev/skills/ngerakines/atproto-skills/atproto-oauth"><img src="https://agentmods.dev/badge/skills/ngerakines/atproto-skills/atproto-oauth/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/ngerakines/atproto-skills/atproto-oauth"><img src="https://agentmods.dev/badge/skills/ngerakines/atproto-skills/atproto-oauth.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 711 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 4,103 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	$0.00711	$0.04103
Opus 5.5	$0.00284	$0.01641
Sonnet 5.5	$0.00142	$0.00821
Haiku 4.5	$0.00071	$0.00410

Measured 2mo ago against content hash de0c0545fa49, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

atproto-oauth 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 2mo ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/validate_client_metadata.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

skills/atproto-oauth/SKILL.md · 194 lines

How it starts

The opening of the file, as written. The whole thing — 194 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AT Protocol OAuth

AT Protocol OAuth is an OAuth 2.1 profile with mandatory PKCE (S256), PAR, DPoP, and URL-based dynamic client registration via a published client metadata document. No client_secret — confidential clients authenticate to the token endpoint with a private_key_jwt assertion (ES256). Public / SPA / native clients authenticate by DPoP proof alone.

This skill routes to per-language guides for Rust, TypeScript, and Go, sitting on top of a language-neutral spec in shared/.

Defaults

client_id is a URL. It resolves to a JSON metadata document the AS fetches on demand. The URL path, host, and protocol must match byte-for-byte between registration, PAR, and authorize.
Every access token is DPoP-bound. dpop_bound_access_tokens: true is required in client metadata; every resource request carries a fresh DPoP proof with ath = SHA-256(access_token) and a per-origin nonce.
PAR is required. You push the authorize request to pushed_authorization_request_endpoint and redirect the user to {AS}/oauth/authorize?client_id=...&request_uri=urn:ietf:params:oauth:request_uri:.... Query parameters never hit the user-agent.
Scopes start with atproto. All flows must request atproto as the first scope. Further scopes are layered on: transition:generic, account:email?action=read, rpc:app.bsky.feed.*, include:<permission-set>, etc.
The session belongs to the DID. sub in the token response is a DID. Handles may change; DIDs don't. Persist by DID.
Identity verification is mandatory: sub → DID document → #atproto_pds → matches the PDS you discovered → authorization_servers[0] → matches the AS you talked to. Skip this step = CSRF window.

Full normative rules: shared/spec.md, shared/flows.md, shared/client-metadata.md, shared/dpop.md, shared/scopes.md, shared/sessions.md, shared/security-requirements.md. Fixtures: shared/test-vectors.md. Common failures: shared/troubleshooting.md. Cross-language differences: shared/divergence-matrix.md.

Read the full file on GitHub · 194 lines

Files

What ships with it

26 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.

2mo ago First seen · 194 lines · 711 tokens per session scan A de0c0545fa49

Subscribe to this mod's changes

atproto-oauth is a skill published in the GitHub repository ngerakines/atproto-skills (53 stars, last pushed 6mo ago), licensed MIT. It adds 711 tokens to every session and 4,103 once invoked, about $0.0028 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.

Backend and APIs Security agentskills atproto atprotocol

atproto-oauth next to 6 skills from other repositories
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atproto-oauthngerakines/atproto-skills	Skill	53	6mo ago	MIT	A	711	Claude Code
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