Honestly this is where I would have fable generate a checklist and you just monitor opus to ensure it is going through the checklist. I think ignore is often the result of a context that is not focused enough.

i've yet to see a case where opus "ignores whatever it likes".

opus will definitely ignore instructions if you give it contradictory instructions, or a plan that has steps that obviously don't work with each other. but if you give it a coherent plan, it will follow it.

Doesn’t that kill your token caching changing models midstream?