Cursor admits its new coding model was built on top of Moonshot AI’s Kimi

Cursor Unveils Composer 2: The Latest in AI Coding Intelligence

Cursor, an AI coding company, made waves this week with the launch of their newest model, Composer 2. Touted as offering “frontier-level coding intelligence,” Composer 2 promises to revolutionize the way developers approach coding tasks.

However, the excitement surrounding Composer 2 was quickly met with skepticism when a user named Fynn pointed out that the new model bore a striking resemblance to Kimi 2.5, an open-source model developed by Moonshot AI, a Chinese company backed by Alibaba and HongShan (formerly Sequoia China).

Fynn’s observations were backed by evidence in the code, which seemed to indicate that Composer 2 was based on the Kimi model. They called out Cursor for not even bothering to rename the model ID, suggesting that Composer 2 was essentially a rebranded version of Kimi 2.5 with some additional reinforcement learning capabilities.

Cursor, a well-funded U.S. startup that boasts impressive financial figures, initially stayed silent on the issue. However, Lee Robinson, Cursor’s vice president of developer education, eventually confirmed that Composer 2 did have its roots in an open-source model, namely Kimi. Robinson clarified that while a portion of the final model was based on Kimi, the majority of the model was developed through Cursor’s own training methods. This, he claimed, resulted in significant differences in performance between Composer 2 and Kimi.

Despite the controversy, Cursor’s use of the Kimi model was deemed to be within the bounds of the licensing agreement, as reiterated by the Kimi account on X. The account congratulated Cursor on their use of the model in what was described as an “authorized commercial partnership” with Fireworks AI.

The Kimi account expressed pride in seeing their model integrated effectively through Cursor’s training methods, emphasizing the collaborative nature of the open model ecosystem.

While Cursor acknowledged that they should have been more transparent about the use of the Kimi base in their initial announcement, co-founder Aman Sanger assured that future models would address this oversight.

The Significance of Building on Chinese Models in the AI Landscape

The controversy surrounding Composer 2’s origins raises questions about the implications of leveraging Chinese models in the competitive AI landscape. With the ongoing narrative of an AI “arms race” between the United States and China, the decision to build on a Chinese model like Kimi could have broader implications for Cursor and the industry as a whole.