# atheris

> Claude/Codex skill by [@trailofbits](https://omgskills.com/library/trailofbits/index.md) · 7.9k stars · Updated 2026-10-28

Sets up and runs Atheris, the coverage-guided Python fuzzer built on libFuzzer. Covers TestOneInput harnesses, FuzzedDataProvider, instrumenting both pure Python and native C extensions, and running under AddressSanitizer. Use when fuzzing a Python package, hunting memory corruption in a Python C extension, or choosing between Atheris and Hypothesis for a Python target.

Tags: agent-skills

## Install

```sh
git clone https://github.com/trailofbits/skills /tmp/skills && ln -s /tmp/skills/plugins/testing-handbook-skills/skills/atheris ~/.claude/skills/atheris
```

## From README

Atheris Atheris is a coverage-guided Python fuzzer built on libFuzzer. It enables fuzzing of both pure Python code and Python C extensions with integrated AddressSanitizer support for detecting memory corruption issues. When to Use | Fuzzer | Best For | Complexity | |--------|----------|------------| | Atheris | Python code and C extensions | Low-Medium | | Hypothesis | Property-based testing | Low | | python-afl | AFL-style fuzzing | Medium | Choose Atheris when: Fuzzing pure Python code with coverage guidance Testing Python C extensions for memory corruption Integration with libFuzzer ecosystem is desired AddressSanitizer support is needed Run: Atheris supports 32-bit and 64-bit Linux, and macOS. We recommend fuzzing on Linux because it's simpler to manage and often faster.

## Links

- HTML page: https://omgskills.com/library/trailofbits/skills/atheris/
- GitHub: https://github.com/trailofbits/skills
- Author: [@trailofbits](https://omgskills.com/library/trailofbits/index.md)

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