Cursor Acknowledges Using Moonshot AI's Kimi Model as Foundation for New Composer 2 Release

The U.S. startup faced criticism for not initially disclosing its use of the open-source Chinese model.

Mar. 22, 2026 at 6:41pm by Ben Kaplan

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AI coding company Cursor launched a new model called Composer 2 this week, which it promoted as offering 'frontier-level coding intelligence.' However, a user soon claimed that Composer 2 was built on top of Moonshot AI's open-source Kimi model. Cursor acknowledged this, saying only about a quarter of the final model's compute came from the Kimi base, with the rest from Cursor's own training. Cursor said using Kimi was consistent with its licensing terms, and Moonshot AI's Kimi account congratulated Cursor on the integration. Cursor's co-founder admitted it was a 'miss' not to mention the Kimi base upfront, citing potential embarrassment and the fraught political climate around U.S.-China AI competition.

Why it matters

This case highlights the complex ecosystem of AI model development, where established companies may build on top of open-source foundations created by others, including international players. It raises questions about transparency, attribution, and the political sensitivities around the global 'AI arms race' between the U.S. and China.

The details

Cursor, a well-funded U.S. AI coding startup, launched Composer 2 this week as its latest model offering 'frontier-level coding intelligence.' However, a user soon claimed the model was essentially a modified version of Moonshot AI's open-source Kimi model, pointing to code that identified Kimi as the base. Cursor acknowledged this, saying about a quarter of the final model's compute came from the Kimi base, with the rest from Cursor's own training. Cursor said its use of Kimi was consistent with the model's licensing terms, and Moonshot AI's Kimi account congratulated Cursor on the integration, calling it part of an 'authorized commercial partnership' with Fireworks AI.

  • Cursor launched Composer 2 this week (March 22, 2026).
  • A user posted the Kimi claims on X (social media platform) shortly after the Composer 2 launch.

The players

Cursor

A well-funded U.S. AI coding startup that launched the Composer 2 model, which was built in part on Moonshot AI's open-source Kimi model.

Moonshot AI

A Chinese AI company backed by Alibaba and HongShan (formerly Sequoia China) that developed the open-source Kimi model, which Cursor used as a foundation for its Composer 2 release.

Fireworks AI

An AI company that had an authorized commercial partnership with Moonshot AI regarding the use of the Kimi model.

Aman Sanger

The co-founder of Cursor who acknowledged it was a 'miss' not to mention the Kimi base upfront in Cursor's announcement of Composer 2.

Lee Robinson

The vice president of developer education at Cursor, who defended the company's use of the Kimi model as consistent with its licensing terms.

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What they’re saying

“Yep, Composer 2 started from an open-source base!”

— Lee Robinson, Vice President of Developer Education, Cursor

“Only ~1/4 of the compute spent on the final model came from the base, the rest is from our training.”

— Lee Robinson, Vice President of Developer Education, Cursor

“Seeing our model integrated effectively through Cursor's continued pretraining & high-compute RL training is the open model ecosystem we love to support.”

— Kimi account

“It was a miss to not mention the Kimi base in our blog from the start. We'll fix that for the next model.”

— Aman Sanger, Co-founder, Cursor

What’s next

Cursor has pledged to be more transparent about its use of open-source models like Kimi in future product releases.

The takeaway

This case highlights the complex and sometimes politically fraught landscape of AI model development, where established companies may build on top of open-source foundations created by international players. It underscores the importance of transparency and attribution, even as companies race to develop the latest cutting-edge AI capabilities.