>Point it at the relevant files and say "the goal is to add X feature to this code, follow Y guidelines".

Is that not how you would work with any model, local or not? I wouldn't trust it to make the right decisions unattended. I just know the moment I look away it's going to do something utterly braindead.

Claude Opus with xhigh thinking is surprisingly good at figuring our details. Granted I'm only using it for little hobby projects, nothing overly complicated.