Harness-1 is a 20B search agent trained using a state-externalizing harness; the author claims it delivers frontier-level long-horizon search rivaling Opus-4.6 and outperforming GPT-5.4 while maintaining Context-1-level cost and latency. The design externalizes candidates, evidence, verification, and search history, is open-source, and was shared with a demo video.
Harness-1 is a 20B search agent trained with a state-externalizing harness; the author claims it enables frontier-level long-horizon search, rivaling Opus-4.6 and outperforming GPT-5.4.
Introducing Harness-1, a 20B search agent trained with a state-externalizing harness.
> frontier-level long-horizon search, rivaling Opus-4.6 and outperforming GPT-5.4
> Context-1-level cost and latency
> externalizes candidates, evidence, verification, and search history
> open-source
Video