GoKawiilAI coding company Cursor launched a new model this week called Composer 2, which it promoted as offering “frontier-level coding intelligence.”
However, an X user 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 AI, a Chinese company backed by Alibaba and HongShan (formerly Sequoia China).
As evidence, Fynn pointed to code that seemed to identify Kimi as the model.
“[A]t least rename the model ID,” they scoffed.
It was a surprising revelation, since Cursor is a well-funded U.S. startup that raised a $2.3 billion round last fall at a $29.3 billion valuation, and is reportedly exceeding $2 billion in annualized revenue. Also, the company didn’t mention anything about Moonshot AI or Kimi in its announcement.
However, Cursor’s vice president of developer education Lee Robinson soon acknowledged, “Yep, Composer 2 started from an open-source base!” But he said, “Only ~1/4 of the compute spent on the final model came from the base, the rest is from our training.” As a result, he said Composer 2’s performance on various benchmarks is “very different” from Kimi’s.
Robinson also insisted that Cursor’s use of Kimi was consistent with the terms of its license, a point the Kimi account on X repeated in a subsequent post congratulating Cursor, where it said Cursor used Kimi “as part of an authorized commercial partnership” with Fireworks AI.
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