Cursor Caught Using Chinese AI Model as Base for 'Frontier' Composer 2, Co-Founder Admits Disclosure Failure

Cursor faces backlash after launching Composer 2 as a 'frontier' coding model without disclosing it's built on Kimi 2.5, a Chinese open-source AI, with co-founder Aman Sanger now admitting the lack of transparency was a mistake amid growing U.S.-China AI tensions.

• Cursor launches Composer 2, marketing it as a frontier-level coding model, but an X user exposes that it is built on top of Kimi 2.5, an open-source model from Chinese AI company Moonshot AI.
• Cursor's VP of developer education confirms the Kimi foundation but emphasizes that roughly three-quarters of the compute used in Composer 2 comes from Cursor's own training, resulting in benchmark performance that differs significantly from the base model.
• Cursor co-founder Aman Sanger admits it was a mistake not to disclose the Kimi base model upfront, with speculation that the omission may be tied to sensitivities around building on a Chinese AI model amid the ongoing U.S.-China AI rivalry.