Composer 2
Cursor · 2026-03-19
Composer 2 is Cursor's agentic coding model, released March 19, 2026, and built from Moonshot's open-weight Kimi K2.5 mixture-of-experts checkpoint through code-focused continued pretraining and large-scale reinforcement learning. Continued pretraining included a 256k-token sequence-length extension; RL training used realistic Cursor sessions with the same tools and harness as deployment and trained self-summarization for long-horizon coding tasks, while the deployed model exposed a 200k-token context window. Cursor retired the `composer-2` SDK identifier in June 2026 and now routes it to Composer 2.5.