Cursor has admitted that its new coding model, Composer 2, builds on top of Moonshot AI’s Kimi model after users flagged similarities soon after launch. The company initially promoted Composer 2 as offering “frontier-level coding intelligence,” but did not mention any connection to Kimi in its announcement.
The issue surfaced when a user on X, posting as Fynn, pointed to code that appeared to identify Kimi as the underlying model. This led to questions about whether Composer 2 was largely based on Kimi 2.5, an open-source model developed by the Chinese company Moonshot AI.
According to statements shared by Cursor executives on X, the company confirmed that Composer 2 started from an open-source base and later added its own training and improvements.
Cursor about Composer 2
Cursor’s vice president of developer education, Lee Robinson, acknowledged the connection and said, “Yep, Composer 2 started from an open-source base!” He explained that only a portion of the compute came from the base model, while most of the work involved Cursor’s own training process.
He also said the final model performs differently from Kimi across benchmarks, which the company attributes to additional reinforcement learning and fine-tuning.
Moonshot AI’s Kimi account also responded publicly, saying Cursor used the model “as part of an authorized commercial partnership” and welcomed the integration as part of the open model ecosystem.
Cursor did not mention Kimi during the launch, which raised concerns about transparency, especially given the company’s scale and valuation. The startup has raised billions and reports strong revenue growth, so expectations around disclosure remain high.
Cursor co-founder Aman Sanger later addressed the issue and said, “It was a miss to not mention the Kimi base in our blog from the start.”
The situation highlights ongoing pressure in the AI industry, where companies build on open models but still face scrutiny over how clearly they communicate those foundations.
