I don't see how you'd avoid using chat if you need the bot to work on some bug end-to-end. I usually have many rounds in a chat session, first asking it to identify the overall approach, reviewing and approving that, then one or more rounds for coding, and several more to request edits as needed.
If you only ever ask it for trivial changes that don't require past context to make sense, then chat is indeed overkill. But we already have different UX approaches for that - e.g. some IDEs watch for specially formatted comments to trigger code generation, so you literally just type what you want right there in the editor, exactly where you want the code to go.
