AI coding company Cursor launched a new model this week called Composer 2, which it [promoted](https://cursor.com/blog/composer-2) as offering “frontier-level coding intelligence.” However, an X user posting under the name Fynn [soon claimed](https://x.com/fynnso/status/2034706304875602030) 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](https://techcrunch.com/2026/01/27/chinas-moonshot-releases-a-new-open-source-model-kimi-k2-5-and-a-coding-agent/), 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](https://techcrunch.com/2025/11/13/coding-assistant-cursor-raises-2-3b-5-months-after-its-previous-round/) at a $29.3 billion valuation, and is [reportedly exceeding $2 billion in annualized revenue](https://techcrunch.com/2026/03/02/cursor-has-reportedly-surpassed-2b-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](https://x.com/leerob/status/2035035355364081694?s=46), “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](https://x.com/Kimi_Moonshot/status/2035074972943831491), where it said Cursor used Kimi “as part of an authorized commercial partnership” with Fireworks AI. Techcrunch event San Francisco, CA | October 13-15, 2026 [REGISTER NOW](https://techcrunch.com/events/tc-disrupt-2026/?utm_source=tc&utm_medium=ad&utm_campaign=disrupt2026&utm_content=tc_inline_eb&promo=tc_inline_eb&display=) “We are proud to see Kimi-k2.5 provide the foundation,” the Kimi account said. “Seeing our model integrated effectively through Cursor’s continued pretraining & high-compute RL training is the open model ecosystem we love to support.” So why not acknowledge Kimi upfront? Beyond any potential embarrassment in not creating a model from scratch, building on top of a Chinese model might feel particularly fraught right now, with the so-called AI “arms race” often framed as [an existential battle between United States and China](https://techcrunch.com/2025/07/23/trumps-ai-strategy-trades-guardrails-for-growth-in-race-against-china/). (See, for example, Silicon Valley’s [apparent panic after Chinese company DeepSeek released a competitive model](https://techcrunch.com/2025/01/30/how-deepseek-changed-silicon-valleys-ai-landscape/) early last year.) Cursor co-founder Aman Sanger [acknowledged](https://x.com/amanrsanger/status/2035079293257359663), “It was a miss to not mention the Kimi base in our blog from the start. We’ll fix that for the next model.”