I've had great success with a tool I wrote that can print sparse ASTs for code.

https://github.com/theduke/smartedit

With the skill installed GPT 5.6 usually automatically uses it, and it reduces code exploration time and token usage significantly, for example by just printing the types and functions in a file without bodies, and only expanding when needed.

(note: it also has editing functionality, which doesn't work so well, since the models are heavily tilted towards common editing tools in post training)