1 min lesson
Inside the Composer 2 training pipeline
Tell someone how to act on this idea: "Composer 2 is that run."
Step 1 of 2
Everything in the prior sections is theory until you see it wired into a real run. Composer 2Cursor's in-house agentic coding model: frontier-level coding quality at high speed and low cost, built as a software-engineering specialist rather than a general-purpose model. Press Enter for the full definition. is that run - long-horizon RLlong-horizon reinforcement learning. Training a coding agent by running many rollouts on real problems and reinforcing the ones that succeed; a single rollout can reach 200K tokens and hundreds of tool calls. Press Enter for the full definition. on real coding problems, in simulated copies of real repos, scored on real test outcomes.
Cursor has described the pipeline in enough detail that you can reason about each stage. Treat this section as the worked example the deep-dive keeps circling back to: where do the problems come from, how does an environment get built, and how do you train past the context window when a single rollout runs huge.
Interactive diagram. Step through it with the Next and Previous controls below, or Tab to a region to read its detail.
Each real coding problem fans out into many rollouts in a simulated repo copy; successes are reinforced, failures are pushed away from - and a prior model builds the environment that grades them.