> The model matters more than the harness anyway
    > 
    > Everyone is benchmaxxing
    > 
    > ...harnesses tend to be chosen on voodoo and hunches...

I get what you're saying, but their graphic on performance here uses the exact same model with different harnesses and definitively shows that there is a significant difference in both accuracy and cost. The whole point of their technical implementation and design decision here is to highlight that it's not "voodoo and hunches", but observable data.

Fable 5 on Claude Code scored 61.8% at a cost of $248.05 while Fable 5 on OpenCode beat it at 66.3% at $73.42. The same model, the same benchmark; only the harness is different with a ~5 point difference in accuracy while costing significantly less. So if we are to believe the author and these results are repeatable, then it would seem that the harness matters.

The point of this framing here is specifically to address 1) benchmaxxing by using the same model, 2) NOT choose a harness on "voodoo and hunches" by using actual data to back the assertions. Your comment feels misguided and completely hand waves the actual data points here.