Currently it can work at function level, and can make reasonable modifications to existing code (sometimes buggy, but that may be fixable with a larger model and better training data).
The current chat UI isn't suitable for working with larger codebases, but it seems within realm of possibility to extend it to be an IDE like CoPilot with tooling that feeds it your whole codebase and documentation to work with.
Currently it can work at function level, and can make reasonable modifications to existing code (sometimes buggy, but that may be fixable with a larger model and better training data).
The current chat UI isn't suitable for working with larger codebases, but it seems within realm of possibility to extend it to be an IDE like CoPilot with tooling that feeds it your whole codebase and documentation to work with.