Borrowing it
Nothing to install: this file belongs to stemma-sh/stemma. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/stemma-sh/stemma/main/CLAUDE.mdgit clone --depth 1 https://github.com/stemma-sh/stemmaWrote 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/instructions/stemma-sh/stemma/claude-md)<a href="https://agentmods.dev/instructions/stemma-sh/stemma/claude-md"><img src="https://agentmods.dev/badge/instructions/stemma-sh/stemma/claude-md/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.
<a href="https://agentmods.dev/instructions/stemma-sh/stemma/claude-md"><img src="https://agentmods.dev/badge/instructions/stemma-sh/stemma/claude-md.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00518 | $0.00518 |
| Opus 5.5 | $0.00207 | $0.00207 |
| Sonnet 5.5 | $0.00104 | $0.00104 |
| Haiku 4.5 | $0.00052 | $0.00052 |
Grade A, and why
stemma CLAUDE.md 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.
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 — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CLAUDE.md
Working conventions for this repository — for humans and coding agents alike. Source comments throughout the codebase cite these rules by name; this file is what they refer to. CONTRIBUTING.md has the full setup and PR expectations; docs/internals/architecture.md is the codemap.
Build & test
mise install # rust (>= 1.91), just, python 3.11 — or install them yourself
just gate # clippy (-D warnings) + full test suite; the merge gate (~8 min)
Prime directive: no silent fallbacks
If input is missing or invalid, decoding fails, or an invariant breaks: return a clear, contextual error (or fail loud at the right place) and stop. Never "best-effort" through an unknown state — continuing in one is the bug.
Ruled out: decode-failure → empty default; unknown enum values mapped to a
catch-all; catch { return ok }; log-and-continue where continuing isn't
provably safe. A default that is part of a contract must be documented,
visibly deliberate, and test-covered. A named isolation boundary that
contains a failure and reports it honestly is fine; absorbing a failure into
apparent success is not.
Model-first
Start from the data: what are the shapes, the allowed states, the allowed transitions? Parse and validate at the edges (wire, file, CLI); the core operates on already-validated domain types. Make invalid states hard to represent. When something breaks, fix where the data first went wrong — not where the failure became visible — and never add downstream tolerance for bad input our own pipeline produced.
Tests encode the domain, not the implementation
A test's expected value must be justifiable from the domain rule (for this repo, that is usually ECMA-376/ISO-29500 semantics or observed real-Word behavior) — never from what the code currently returns. When fixing a bug: correct the test first, then the code. Characterization tests are allowed but must be labeled as such.
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 · 51 lines · 518 tokens per session scan A 82a135b65bbc
stemma CLAUDE.md is an instructions file published in the GitHub repository stemma-sh/stemma (23 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 518 tokens to every session, about $0.0021 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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