What is cs4ai?

CS4AI, also called cs4ai, is a command line tool that lets an AI coding agent read and edit C# code in a more precise way than just editing raw text files. Instead of an AI opening a file and guessing where to change lines, cs4ai understands the actual structure of the code, such as classes and methods by name, using a technology called Roslyn that Microsoft built for understanding C# programs. When an agent works with cs4ai, it starts a session pointed at a project, then can inspect a piece of code, create a new method, rename something everywhere it is used, move a piece of code to a different class, or delete it, all by referring to the code's actual name rather than a line number. Every edit is written straight to the project files immediately, and the tool reports back whether the project still builds and whether tests still pass after each change, so the agent always knows if it just broke something. Undoing changes is left to version control tools like git rather than being built into cs4ai itself. To prevent an agent from editing code based on outdated information, every piece of code it reads comes with a token that marks its current state, and if the agent tries to edit using an old token, cs4ai refuses and shows the current version instead. There is also a companion feature that lets cs4ai install itself as a skill for Claude Code, the AI coding assistant, so an agent using that tool can pick up the same capabilities automatically. The project is described as a release candidate, tested with 138 passing tests, requires the .NET 10 SDK to install, and has only been built and tested on Windows so far, with Linux support untested. It has 3 stars, and the README does not state a license.