While building Codegen, we took a detour to solve a problem that kept blocking our agents: making large-scale, structural changes to a codebase reliably. The answer was graph-sitter — an open-source library for programmatic codebase refactors, built on top of Tree-sitter.
Instead of nudging files one edit at a time, graph-sitter builds an in-memory graph of a codebase — functions, classes, imports, and their relationships — and exposes high-level APIs that match how engineers actually think about refactors and migrations. It became the foundation for our "act via code" thesis.
We first put that foundation behind an IDE built specifically for refactors — see the demo here.
The thesis behind it
Act via Code
Why the next step for software agents is a more expressive action space — writing and executing programs against well-designed APIs.
Links & milestones
IDE for refactors
Announcing an IDE purpose-built for codebase refactors.
Open-source release
Introducing graph-sitter as an open Python library for manipulating codebases.
graph-sitter.dev
The project site and docs.
Jay Hack, Founder