Cursor admits its new coding model was built on Kimi from Moonshot AI | TechCrunch

AI coding company Cursor launched a new model this week called Composer 2, which it promoted as offering “frontier-level coding intelligence.”

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

As proof, Fynn pointed to a code that appeared to identify Kimi as the model.

“[A]At least rename the model ID,” they scoffed.

This was a surprising revelation, since Cursor is a well-funded American startup that raised a $2.3 billion fundraising round last fall at a valuation of $29.3 billion, and is would have exceeded $2 billion in annualized revenue. Additionally, the company didn’t mention anything about Moonshot AI or Kimi in its announcement.

However, Cursor’s VP of Developer Education Lee Robinson quickly recognized“Yes, Composer 2 started from an open source base!” But he said: “Only about 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 that Composer 2’s performance on various criteria is “very different” from Kimi’s.

Robinson also insisted that Cursor’s use of Kimi was within the terms of its license, a point that the Kimi account on next post praising the cursorwhere he said Cursor used Kimi “as part of a permitted commercial partnership” with Fireworks AI.

“We are proud to see Kimi-k2.5 forming the basis,” says the Kimi account. “Seeing our model integrated effectively through ongoing pre-training and high-computing RL training from Cursor is the open model ecosystem we love to support.”

So why not recognize Kimi from the start? Beyond any potential embarrassment of not building a model from scratch, building on a Chinese model might seem particularly difficult right now, with the so-called AI “arms race” often touted as an existential battle between the United States and China. (See, for example, the Silicon Valley report Apparent panic after Chinese company DeepSeek releases competitive model early last year.)

Aman Sanger, co-founder of Cursor recognized“It was a mistake not to mention the Kimi base in our blog from the beginning. We will correct this for the next model.”

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