Cursor Admits New Composer 2 Coding Model Was Built on Chinese AI Kimi K2.5

Cursor quietly launched Composer 2, a new coding model it described as frontier-level intelligence, without disclosing it was built on top of Kimi K2.5, an open-source model from Moonshot AI, a Chinese startup backed by Alibaba, Tencent, and HongShan (formerly Sequoia China). A developer named Fynn uncovered the connection by routing Cursor's API traffic through a debug proxy and finding the model ID in plain text. Cursor co-founder Aman Sanger acknowledged the omission was a mistake. VP of Developer Education Lee Robinson confirmed about a quarter of the model's compute derives from the Kimi base. Kimi K2.5 is a 1 trillion parameter mixture-of-experts model with 32 billion active parameters, a 256,000-token context window, and native image and video support. The disclosure raises broader questions about how many Western AI products are built on Chinese open-source foundations, especially as export controls and AI sovereignty concerns intensify.