Borrowing it
Nothing to install: this file belongs to ReviewToolkits/cext-review-toolkit. 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/ReviewToolkits/cext-review-toolkit/main/CLAUDE.mdgit clone --depth 1 https://github.com/ReviewToolkits/cext-review-toolkitWrote 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/reviewtoolkits/cext-review-toolkit/claude-md)<a href="https://agentmods.dev/instructions/reviewtoolkits/cext-review-toolkit/claude-md"><img src="https://agentmods.dev/badge/instructions/reviewtoolkits/cext-review-toolkit/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/reviewtoolkits/cext-review-toolkit/claude-md"><img src="https://agentmods.dev/badge/instructions/reviewtoolkits/cext-review-toolkit/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 | $0.02660 | $0.02660 |
| Opus 5 | $0.01330 | $0.01330 |
| Sonnet 5 | $0.00532 | $0.00532 |
| Haiku 4.5 | $0.00266 | $0.00266 |
Grade A, and why
cext-review-toolkit 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 8d 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 — 180 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CLAUDE.md — cext-review-toolkit development guide
Project overview
cext-review-toolkit is a Claude Code plugin for reviewing CPython C extensions. It finds API misuse, memory safety bugs, compatibility issues, and correctness problems in code that consumes the Python/C API.
Part of a family of review toolkits:
- code-review-toolkit — Python source code
- cpython-review-toolkit — CPython runtime C code
- cext-review-toolkit — C extensions (this project)
Key architectural difference: uses Tree-sitter for C parsing (not regex), enabling analysis that regex cannot do (borrowed-ref lifetime tracking, type slot cross-referencing, accurate scope analysis).
Prerequisites
- Python 3.10+
tree-sitterandtree-sitter-c:pip install tree-sitter tree-sitter-ctree-sitter-cpp(optional):pip install tree-sitter-cpp— enables C++ file parsingclang-tidyandcppcheck(optional): system packages — enables external tool cross-referencing- No other dependencies — all scripts use only the standard library plus tree-sitter
Dev commands
# Activate the project venv (Python 3.14 from ~/projects/3.14/python)
source ~/venvs/cext-review-toolkit/bin/activate
# Run all tests
python -m unittest discover tests -v
# Run a specific test file
python -m unittest tests.test_scan_refcounts -v
# Run a single script standalone (all output JSON to stdout)
python plugins/cext-review-toolkit/scripts/scan_refcounts.py /path/to/extension.c
python plugins/cext-review-toolkit/scripts/discover_extension.py /path/to/project
# Lint and format (install ruff/mypy into venv if not present)
ruff format <changed-files>
ruff check <changed-files>
mypy
Code style
- Python 3.10+ (uses
X | Yunion syntax) - Double quotes for strings
- Type hints on all function signatures
- Docstrings on classes and public functions
- Tests use
unittest— never pytest - Linted and formatted with ruff, type checked with mypy
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.
- 8d ago First seen · 180 lines · 2,660 tokens per session scan A a2b6fcce00f1
cext-review-toolkit CLAUDE.md is an instructions file published in the GitHub repository ReviewToolkits/cext-review-toolkit (28 stars, last pushed 1mo ago), licensed MIT. It adds 2,660 tokens to every session, about $0.0133 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 2026-08-30.
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