Cursor has released Composer 2.5, a significant upgrade to its AI coding agent. Key improvements include targeted RL with textual feedback for more precise credit assignment during training, 25x more synthetic tasks than Composer 2 (including feature deletion tasks grounded in real codebases), and infrastructure advances like Sharded Muon with distributed orthogonalization and dual mesh HSDP for MoE models. The model is built on Moonshot's Kimi K2.5 checkpoint and is better at long-horizon agentic tasks, complex instruction following, and communication style. Pricing starts at $0.50/M input and $2.50/M output tokens, with a faster variant available. Cursor is also training a significantly larger model from scratch with SpaceXAI using 10x more compute on Colossus 2.
