Cursor Composer 2.0 = Kimi K2.5 with RL: License Breach Allegation, Resolved via Authorized Partnership

Simon Willison·high signal

Cursor shipped Composer 2 on March 19 billing it as a proprietary in-house model; within 24 hours a developer found the API routing to `kimi-k2p5-rl-0317-s515-fast`. Moonshot AI initially flagged a Modified MIT License violation (Cursor exceeds the 20M/month revenue threshold requiring prominent Kimi attribution in UI), but Moonshot subsequently confirmed Cursor accesses Kimi K2.5 via Fireworks AI under an authorized commercial deal. Cursor acknowledged the omission from its blog post as 'a mistake' and committed to naming base models in future releases.