Composer

Composer was released by Cursor on October 29, 2025 as an agent model for software engineering. It used a mixture-of-experts architecture and reinforcement learning in development environments equipped with search, editing and terminal tools. Cursor designed it for interactive use, where repeated reasoning and tool calls needed to feel fast enough for a programmer to stay involved.

The training emphasized solving problems inside large codebases, including respecting existing abstractions rather than merely producing code that passed a narrow test. Cursor's own evaluation measured real requests from its engineers and researchers. The model was developed for use inside Cursor, with the surrounding editor and agent tools supplying repository access and executing the model's requested actions.