Even the /handoff skill was written by the model…
I also imagine that varies by model.
It should be a first class feature of the harness, tbh. It kind of is with the /compact [focus] parameter but this is coarse and leaves no record. I find keeping the handoff files in the repo to be useful for historical context and later debugging.
The solution that I've developed is, let the agent figure things out efficiently, without inflating the context. I have what I call a smart repo that better explains this at
https://github.com/gitsense/smart-ripgrep
The basic idea is, when the agent does a ripgrep it gets back files + matching lines + context.