Cursor admits that the new coding model is based on Moonshot AI’s Kimi

AI coding company Cursor launched a new model this week called Composer 2 has been moved forward as offers “borderline coding intelligence”.

However, an X user posts under the name Fynn soon claimed This Composer 2 was “only Kimi 2.5” with additional reinforcement learning – Kimi 2.5 An open source model recently released by Moonshot AIA Chinese company backed by Alibaba and HongShan (formerly Sequoia China).

As evidence, Fynn pointed to a code that identified Kimi as a model.

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

It was a surprising discovery because Cursor is a well-funded US startup in the autumn of last year, it collected a turnover of 2.3 billion dollars It is worth 29.3 billion dollars it is reported that its annual income exceeds 2 billion dollars. Also, the company didn’t mention anything about Moonshot AI or Kimi in its announcement.

However, Kursor’s vice president of developer education Lee Robinson soon admitted“Yes, Composer 2 started from open source!” But he said, “Only ~1/4 of the computation spent on the final model came from the base, the rest came from our training.” As a result, he said Composer 2’s performance on various benchmarks was “very different” from Kim’s.

Robinson also insisted that Cursor’s use of Kimi was in accordance with the terms of his license, which I reiterate in his account of Kimi in X . A subsequent post congratulating the cursorwhere it says Cursor Kimi is used “as part of an authorized commercial partnership” with Fireworks AI.

“We are proud to see Kimi-k2.5 provide the foundation,” said Kimi’s account. “Seeing our model integrate effectively through ongoing Cursor training and highly computational RL training is an open model ecosystem we love to support.”

So why don’t you acknowledge Kim in advance? Building on the Chinese model, rather than creating a model from scratch, can feel especially difficult in the current so-called AI “arms race.” The existential battle between the US and China. (See, for example, Silicon Valley Open panic after the Chinese company DeepSeek released a competing model early last year.)

Cursor co-founder Aman Sanger he admitted“It was a mistake not to mention the Kimi base on our blog from the beginning. We will fix it for the next model.”