That sounds more like a spec change than a set of bug fixes, even if the conclusion is that the potentially implicit spec you started with was incorrect. I've had an interesting experience extracting a spec from some existing code, making some modifications, then saying basically "implement this spec, don't come back until you're done".

An interesting experiment would be to try having the agent annotate the code with the relevant spec section while it's extracting the spec, then to have the agent update the spec with the new requirement - as an explicit change with something like "This section updated in V2 with...." - and have the agent update the codebase from that.

Some of these problems do just need breaking down a little further than you'd think to make the agent's life easier. This might be one of them.