humans& launches Persimmon, a 550B-parameter user model that simulates real human behavior
CShorten30 · x · 2026-09-25
humans& released Persimmon, a research-preview "user model" designed to realistically simulate how people behave in multi-turn, multi-user chats — not an assistant. Mid/post-trained from NVIDIA's 550B Nemotron 3 Ultra on public human-to-human conversations using thousands of Blackwell GPUs. Its conversations are significantly harder to distinguish from real humans than frontier models prompted to act as people. Released with evaluations measuring how faithfully user models capture human behavior.
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