Whatever work is paying for on a given day. We've rotated through a few offerings. It's a work truck not a personal vehicle, for me.
I manage a team of interns and I don't have the energy to babysit an agent too. For me, gpt and gemini yield the best talk-it-through approach. For example, dropping a research paper into the chat and describing details until the implementation is clarified.
We also use Claude and Cursor, and that was an exceptionally disruptive experience. Huge, sweeping, wrong changes all over. Gyah! If I bitch about todo! macros, this is where they came from.
For hobby projects, I sometimes use whatever free agent microsoft is shilling via VS Code (and me selling my data) that day. This is relatively productive, but reaches profoundly wrong conclusions.
Writing for CLR in visual studio is the smoothest smart-complete experience today.
I still experience agents slipping in a `todo!` and other hacks to get code to compile, lint, and pass tests.
The loop with tests and doc tests are really nice, agreed, but it'll still shit out bad code.