Cursor Admits Its New Coding Model Was Built On Top Of Moonshot Ai’s Kimi

AI coding institution Cursor launched a caller exemplary this week called Composer 2, which it promoted arsenic offering “frontier-level coding intelligence.” 

However, an X personification posting nether nan sanction Fynn soon claimed that Composer 2 was “just Kimi 2.5” pinch further reinforcement learning — Kimi 2.5 being an unfastened root exemplary precocious released by Moonshot AI, a Chinese institution backed by Alibaba and HongShan (formerly Sequoia China). 

As evidence, Fynn pointed to codification that seemed to place Kimi arsenic nan model.

“[A]t slightest rename nan exemplary ID,” they scoffed.

It was a astonishing revelation, since Cursor is simply a well-funded U.S. startup that raised a $2.3 cardinal information past fall astatine a $29.3 cardinal valuation, and is reportedly exceeding $2 cardinal successful annualized revenue. Also, nan institution didn’t mention thing astir Moonshot AI aliases Kimi successful its announcement.

However, Cursor’s vice president of developer acquisition Lee Robinson soon acknowledged, “Yep, Composer 2 started from an open-source base!” But he said, “Only ~1/4 of nan compute spent connected nan last exemplary came from nan base, nan remainder is from our training.” As a result, he said Composer 2’s capacity connected various benchmarks is “very different” from Kimi’s.

Robinson besides insisted that Cursor’s usage of Kimi was accordant pinch nan position of its license, a constituent nan Kimi relationship connected X repeated successful a subsequent station congratulating Cursor, wherever it said nan Cursor utilized Kimi “as portion of an authorized commercialized partnership” pinch Fireworks AI.

“We are proud to spot Kimi-k2.5 supply nan foundation,” nan Kimi relationship said. “Seeing our exemplary integrated efficaciously done Cursor’s continued pretraining & high-compute RL training is nan unfastened exemplary ecosystem we emotion to support.”

So why not admit Kimi upfront? Beyond immoderate imaginable embarrassment successful not creating a exemplary from scratch, building connected apical of a Chinese exemplary mightiness consciousness peculiarly fraught correct now, pinch nan alleged AI “arms race” often framed arsenic an existential conflict betwixt United States and China. (See, for example, Silicon Valley’s apparent panic aft Chinese institution DeepSeek released a competitory model early past year.)

Cursor co-founder Aman Sanger acknowledged, “It was a miss to not mention nan Kimi guidelines successful our blog from nan start. We’ll hole that for nan adjacent model.”