Hmm. When I have Opus or Fable write build plans, then invariably invariably read code extensively, but it’s true they don’t make changes and run tests.

I guess the way to formalize this would be to add a “make minimal change to confirm approach” instruction to the build planning prompt. Probably can even parallelize that so as the build planning prompt iterates subagents get launched to validate, similar to what research modes do.

I’m a little skeptical, but will give it a try.