title: CouchPilot: Autonomous Repository Housekeeping with Guaranteed AST Equivalence
What We Built Most AI coding assistants operate with unconstrained blast radiuses: when asked to document or format code, they rewrite entire functions, subtly change control flow, introduce hallucinations, or silently alter edge-case semantics. For open-source maintainers, reviewing AI-generated pull requests often requires more cognitive overhead than writing the code from scratch. We built…
CouchPilot is an autonomous system designed to maintain Python repositories through automated documentation and type annotation management. It aims to preserve functional code immutability through a deterministic process. The system utilizes tree-sitter to identify code elements that require updates, such as missing docstrings or unannotated function signatures.
The LLM is not used to guess what needs fixing but instead generates docstrings and type hints using open-weight Google Gemma models. The generated content adheres to specific Pydantic JSON schemas and is strictly confined to docstrings and type hints, with no interference in function bodies. Before applying any changes, CouchPilot verifies the AST equivalence between the original and updated code using Python's standard library ast module.
If the stripped trees, devoid of docstrings and type annotations, are not identical, the patch is rejected. The system operates within isolated Git worktrees to protect the default branch, and verified patches are committed to separate review branches. A web dashboard on Render provides maintainers and judges with detailed audit reports, including unified diffs and performance traces.
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