Cursor maker Anysphere shipped Composer 2 as an in-house model without disclosing it was built on Moonshot AI's open-weight Kimi K2.5
Mar 19, 2026Anysphere launched 'Composer 2' inside its Cursor code editor on March 19, 2026, marketing it as frontier in-house coding intelligence without disclosing its base model. Within days, a developer identified the underlying model fingerprint as Moonshot AI's open-weight Kimi K2.5, and Moonshot's head of pretraining publicly accused Cursor of violating Kimi's modified-MIT license (which requires prominent 'Kimi K2.5' UI attribution and licensing fees above $20M in monthly revenue or 100M MAU -- thresholds Cursor's roughly $2B annualized revenue clearly exceeds) without paying fees. Cursor VP Lee Robinson and co-founder Aman Sanger acknowledged Composer 2 started from the open-source Kimi base, with Sanger calling the lack of disclosure in Cursor's launch blog post 'a miss.' Moonshot separately stated Cursor's use came through an authorized commercial partnership with Fireworks AI, muddying the licensing-violation claim.