# When changing a public interface, all callers must be updated in the same atomic commit

### The contract-change check (mandatory for any edit that changes a public interface)

Before any edit, search the codebase for callers of the function/symbol/yield shape you're changing. If your edit changes:

- A function signature (add/remove/rename a parameter)
- A return type or yield shape (e.g. `yield process, gui_script` -> `yield process, gui_script, workspace_path`)
- A class hierarchy (add/remove a base class, change a method's name)
- A module-level function name (rename)
- A public attribute name

...you MUST update ALL callers in the same atomic commit. Use `py_find_usages` to locate them. If you change a contract and don't update callers, you have broken the codebase.