Personally I prefer my harness to be open source. So Opencode/pi.dev seem the best for me.

I suppose that as your original comment mentioned Kimi being a nice model with a good harness, My personal opinion suggests for me saying that Kimi with opencode might make it competent model too. Although currently I just use the model provided by default on opencode and I have found it to be competent for small codebases itself, although you definitely have to ask it to git/jj.

The Opencode default model consensus seems to be GLM 4.6 and Kimi 2.6 is definitely much more competent model

I think that tools like Opencode might continue getting better too given its open nature if/as the harness itself turns out to be the most valued piece for a model's competence as you suggested, so I am betting on Opencode and I really appreciated this discussion we had as It was great to know insider insights and I wish you good luck for your product!