On March 19, 2026, Cursor, an AI programming assistant based in the United States, unveiled its Composer 2 model, touting it as having "state-of-the-art programming intelligence." However, an X platform user named Fynn uncovered that the model is, in fact, a modified version of the open-source Kimi 2.5 model from the Chinese AI company Moonshot AI, refined exclusively through reinforcement learning techniques. Cursor later confirmed that Composer 2 was developed based on Kimi 2.5 as part of an authorized collaboration, and it apologized for not promptly disclosing details about the foundational model. Moonshot AI officially verified the partnership, noting that Cursor secured commercial authorization for Kimi 2.5 via the third-party platform Fireworks AI.

Specifically designed for long-cycle agent programming, Composer 2 supports a context window of 200,000 tokens and delivers exceptional performance across multiple benchmark tests, outperforming competitors like Claude Opus 4.6. Its pricing is set at a competitive rate of $0.5 per million input tokens and $2.5 per million output tokens, which is just one-tenth the cost of similar models on the market. This collaboration is viewed as a significant validation of the capabilities of Chinese AI open-source models. At the same time, it has ignited discussions regarding how commercial companies should strike a balance between technological transparency and commercial branding when leveraging open-source models.