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

AI coding company Cursor launched a new model this week called Composer 2 Promoted As offering “coding intelligence at the frontier level”.

However, User X is posting under the name Fynn He claimed soon That Composer 2 was “just Kimi 2.5” with added reinforcement learning – Kimi 2.5 is An open source model recently released by Moonshot AIa Chinese company backed by Alibaba and Hongshan (formerly Sequoia China).

As proof, Finn pointed to the code that seemed to identify Kimmy as a model.

“(A)at least rename the model ID,” they scoffed.

It was a surprising discovery, given that Cursor is a well-funded American startup It raised a $2.3 billion round last fall With a valuation of $29.3 billion, it is Annual revenue is said to exceed $2 billion. The company also didn’t mention anything about Moonshot AI or Kimi in its announcement.

However, Cursor’s Vice President of Developer Education Robinson quickly confessed to me“Yes, Composer 2 started from an open source base!” But he said: “Only a quarter of the compute spent on the final model came from the base, and the rest from our training.” As a result, he said, Composer 2’s performance across various benchmarks is “quite different” from Kimi’s.

Robinson also insisted that Cursor’s use of Kimi was consistent with the terms of its license, a point reiterated by Kimi’s account on X in Yet another congratulations pointerIt said Cursor used Kimi “as part of an approved commercial partnership” with Fireworks AI.

“We are proud to see Kimi-k2.5 providing the foundation,” Kimi’s account said. “Seeing our model effectively integrated through continuous Cursor pre-training and high-compute RL training is the open model ecosystem we love supporting.”

So why don’t we acknowledge Kimmy upfront? Aside from any potential embarrassment in not creating a model from scratch, building on the Chinese model may seem particularly risky right now, as the so-called AI “arms race” is often framed as An existential battle between the United States and China. (See, for example, Silicon Valley Clear panic after Chinese company DeepSeek released a competitive model early last year.)

Cursor co-founder Aman Sanger I confess“It was a mistake not to mention Kimi’s rule in our blog from the beginning. We will fix that for the next model.”