Anecdotally, it feels like Opus, Fable, and Sol "get distracted" when you use them for writing code. Great at reasoning and coordination but they will go off on a tangent and refactor half the code base. I only use them for reasoning (of course) and coordinating subagents.
mind sharing hints/links on your harness/flow setup?
I did several attempts with naive prompting, but spent more time babysitting than actual flow