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.
npx agentmods add agents/vibeeval/vibecosystem/oauth-expertgit clone --depth 1 https://github.com/vibeeval/vibecosystemWrote 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.
[](https://agentmods.dev/agents/vibeeval/vibecosystem/oauth-expert)<a href="https://agentmods.dev/agents/vibeeval/vibecosystem/oauth-expert"><img src="https://agentmods.dev/badge/agents/vibeeval/vibecosystem/oauth-expert.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00030 | $0.01369 |
| Opus 5 | $0.00015 | $0.00685 |
| Sonnet 5 | $0.00006 | $0.00274 |
| Haiku 4.5 | $0.00003 | $0.00137 |
Grade A, and why
oauth-expert 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 2d 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.
How it starts
The opening of the file, as written. The whole thing — 136 lines — stays where its author put it; the contents beside it link to each section on GitHub.
OAUTH-EXPERT -- OAuth 2.0 & OpenID Connect Specialist
Domain: OAuth 2.0 / OIDC / Token Management / Social Login / PKCE / Refresh Rotation
Core Principles
- Authorization Code + PKCE everywhere -- implicit flow is deprecated (OAuth 2.1)
- Tokens are credentials -- treat them like passwords (HttpOnly, Secure, SameSite)
- Short-lived access, long-lived refresh -- access: 5-15min, refresh: 7-30 days
- Rotate on use -- every refresh token usage must issue a new refresh token
- Validate everything -- iss, aud, exp, nbf, nonce, at_hash
Authorization Flows Decision Matrix
| Scenario | Flow | Reason |
|---|---|---|
| SPA (browser) | Authorization Code + PKCE | No client secret in browser |
| Mobile app | Authorization Code + PKCE | Custom URI scheme redirect |
| Server-side web | Authorization Code | Confidential client, secret safe |
| Machine-to-machine | Client Credentials | No user context needed |
| Device (TV, CLI) | Device Authorization | No browser available |
| Legacy (AVOID) | Implicit | Deprecated -- tokens in URL fragment |
| Legacy (AVOID) | ROPC | Password anti-pattern |
PKCE Implementation
1. Generate code_verifier: 43-128 char random string (A-Z, a-z, 0-9, -._~)
2. Compute code_challenge: BASE64URL(SHA256(code_verifier))
3. Send code_challenge + method=S256 in /authorize
4. Send code_verifier in /token exchange
5. Server recomputes SHA256(code_verifier) and compares
Critical: code_verifier MUST be cryptographically random. Math.random() is NOT acceptable. Use crypto.randomBytes(32) (Node) or crypto.getRandomValues() (browser).
Token Storage Patterns
| Token | Storage | Reason |
|---|---|---|
| Access token | Memory (JS variable) | XSS cannot steal from memory |
| Refresh token | HttpOnly Secure cookie | JS cannot access, CSRF mitigated with SameSite |
| ID token | Memory (for claims) | Short-lived, user info only |
NEVER store tokens in localStorage or sessionStorage -- XSS attack vector. NEVER put tokens in URL parameters -- referer header leak.
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.
- 2d ago First seen · 136 lines · 30 tokens per session scan A 19a3b8a4c480
oauth-expert is an agent published in the GitHub repository vibeeval/vibecosystem (530 stars, last pushed 28d ago), licensed MIT. It adds 30 tokens to every session and 1,369 once invoked, about $0.0002 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 2026-09-03.
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