What is biston?

biston is a structural clone detector and refactor suggester for Python. It parses your code with tree-sitter, normalizes each function into a canonical AST, and finds groups of functions that are structurally similar — even when local names, literals, and argument order differ. For each match it can also propose an anti-unified template with typed “holes” that you could extract into a shared helper.

Written in Rust and distributed as a Python package, biston runs fast enough to drop into CI pipelines.

Who it’s for

• Python teams tracking copy-paste drift across modules as a codebase grows.
• CI pipelines that want SARIF output wired into code-quality dashboards.
• AI coding agents (and the humans reviewing their PRs) where boilerplate tends to accumulate function by function.

Working with a coding agent

biston explains itself, so you do not have to. Hand your agent one line:

Run uvx biston guide at the root of this repo and follow what it says.

It prints what to do at the moment you are actually in — Setup when the repo has no biston config, Triage when it does — and a scan that reports clones ends with a footer pointing back at biston guide triage. Tune is the reference for suppression and the policy keys. The CLI and these pages serve the same bytes.

Next

• How It Works — the pipeline, from discovery to anti-unified templates.

Machine-readable docs

Every page on this site is also served as raw Markdown, following the llms.txt convention:

• llms.txt — compact index with links to every page as .md.
• llms-full.txt — all pages concatenated into a single document.

Drop either one into an LLM context window to give the model the full picture without scraping HTML.