Show HN: Zenith: sota harness for normal models to beat Fable on FrontierSWE

Zenith is our long-running agent harness. On Frontier SWE — seventeen of the hardest public long-horizon software-engineering tasks we know of — Zenith took GPT-5.5 from 5th place to 1st, ahead of Claude Fable, by building the right harness around the model instead of swapping in a bigger one.