Codegen – OSS Python Library for Advanced Code Manipulation

In plain words

Codegen is an open-source Python library for programmatically manipulating Python and JavaScript/React codebases. It provides a scriptable interface to a language server built on Tree-sitter, enabling developers to perform large-scale refactoring, pattern enforcement, and control flow analysis. Designed for teams working with multi-million-line enterprise codebases, it abstracts away AST complexity to let developers express code transformations in high-level terms rather than parser internals.

written from the facts on this page · September 2026

From the sources

Code agents accessible via API, Slack, Linear, Github, and more.

In the maker’s words, at launch

Hey HN! We've just open-sourced Codegen (https://github.com/codegen-sh/codegen-sdk), a Python library for manipulating Python + JS/React codebases. Codegen was engineered backwards from real-world, large-scale codebase analysis + refactors we performed on multi-million-line enterprise…

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