Cursor Composer 2 Accused of Using Kimi K2.5 Model, Moonshot AI Alleges License Violation

Gate News reports that on March 20, according to 1M AI News monitoring, developer @fynnso discovered while debugging Cursor API requests that the actual model ID for Composer 2 is kimi-k2p5-rl-0317-s515-fast, literally “Kimi K2.5 + RL.” Moonshot AI’s pretraining lead Du Yulun immediately tweeted that after testing Composer 2’s tokenizer, they found it to be “completely identical to our Kimi tokenizer,” and “almost certain that this is our model further retrained,” directly tagging Cursor co-founder Michael Truell and questioning, “Why is our license not respected, and no payment has been made?” When Cursor released Composer 2 on March 19, they claimed performance improvements came from “continued pretraining of the base model combined with reinforcement learning,” but made no mention of Kimi K2.5. Kimi K2.5 uses a modified MIT license, explicitly stating that commercial products with over 100 million active users or over $20 million in monthly revenue must prominently display “Kimi K2.5” in the user interface. With Cursor valued at $29.3 billion and a paying user base, the monthly revenue threshold almost certainly triggers this requirement. As of press time, Cursor has not publicly responded.