March 22, 2026 — AI coding startup Cursor has confirmed that its newly launched Composer 2 model was built using Moonshot AI’s open-source Kimi model as a base, following online claims that questioned the model’s origins. The company’s vice president of developer education, Lee Robinson, acknowledged the foundation after an X user identified code linking Composer 2 to Kimi.
Revelation and Response
Cursor promoted Composer 2 this week as offering “frontier-level coding intelligence.” Shortly after, a user posting as Fynn on X asserted the model was “just Kimi 2.5” with added reinforcement learning. Kimi 2.5 is an open-source model from Chinese company Moonshot AI, which is backed by Alibaba and HongShan.
As evidence, Fynn pointed to code that appeared to identify Kimi. Cursor’s initial announcement did not mention Moonshot AI or the Kimi model. Robinson later stated on X, “Yep, Composer 2 started from an open-source base!” He clarified that only about a quarter of the compute spent on the final model came from the base, with the remainder from Cursor’s own training.
Performance and Partnership Claims
Robinson argued the resulting model’s performance on benchmarks is “very different” from Kimi’s. He also insisted Cursor’s use complied with Kimi’s license. The official Kimi account on X supported this, stating Cursor used the model “as part of an authorized commercial partnership” with Fireworks AI.
“We are proud to see Kimi-k2.5 provide the foundation,” the Kimi account posted. “Seeing our model integrated effectively through Cursor’s continued pretraining & high-compute RL training is the open model ecosystem we love to support.”
Transparency and Geopolitical Context
The omission of Kimi in the launch materials raised questions. Building on a Chinese model carries particular sensitivity amid frequent framing of AI development as a competitive race between the United States and China. Industry observers noted similar reactions followed the release of a competitive model by Chinese firm DeepSeek early last year.
Cursor co-founder Aman Sanger admitted the oversight. “It was a miss to not mention the Kimi base in our blog from the start,” Sanger said. “We’ll fix that for the next model.”
Company Profile and Market Position
Cursor is a well-funded U.S. startup. It raised a $2.3 billion funding round last fall, achieving a $29.3 billion valuation. The company is reportedly exceeding $2 billion in annualized revenue. The incident highlights the complex, interconnected nature of the global AI development ecosystem, where open-source foundations from various countries are routinely built upon and refined.
For more information on open-source AI model licensing, developers can review resources from the Open Source Initiative. Official model releases are often documented on repositories like GitHub.
This article was produced with AI assistance and reviewed by our editorial team for accuracy and quality.
