What harness? And why not just Fable+Opus?

Personally I use only one family for code editing, other families for code navigation.

Models tend to reason about the code using their own intuition and putting other families onto the same codebases may end up with them getting confused. Esp if that other model is as unhinged as Grok.

Also, harness matters a ton. Use a wrong harness with a good model and you’ll get terrible results.