Cua founder Francesco Bonacci open-sourced CUA-S1-FORMS on September 18, 2026 — a 706,048-parameter “System One” model that plans form-filling actions in a single forward pass. The MIT-licensed release includes a 2.8 MB checkpoint, training code, synthetic-data generation, and evaluation tooling.
The model scores predefined options (select document value, check, click, skip) rather than generating text token-by-token. Cua Driver executes the selected plan. Reported accuracy: 99.95% on synthetic tests and 100% on a 196-decision real-form demo, though the model cannot invent values and has limited real-world validation.
Bonacci previously worked at Xbox and Microsoft AI, co-authored Windows Agent Arena, founded Cua in 2025 after leaving Microsoft, and joined Y Combinator Spring 2025. Cua’s main repo had ~23,300 GitHub stars as of September 19, 2026.