xAI Integrates Cursor's "Composer 2.5" into Grok Build

On June 1, 2026, xAI officially announced that Cursor's (Anysphere) coding-specialized model "Composer 2.5" is now available within its own terminal-based coding agent "Grok Build." It is offered as a fast model strong at long-running tasks and following complex instructions.

What Happened

The official xAI account (@xai) announced on June 1 that Composer 2.5 is now selectable within Grok Build, accompanied by a short demo video. The company positions the model as "fast, highly intelligent, and excellent at long-running tasks and following complex instructions." Announcement

Composer 2.5 is Cursor's in-house coding model officially released on May 18, 2026, and this time xAI has integrated it into its own product "Grok Build." Cursor official

Grok Build is a Rust-based coding agent CLI that xAI released in beta in mid-May 2026, featuring up to 8 parallel sub-agents, a "Plan mode" that reviews and approves plans before execution, and compatibility with existing plugins and workflows. It is offered to SuperGrok / X Premium Plus subscribers. xAI official

Background and Significance

Composer 2.5 is Cursor's in-house model built on a checkpoint of Moonshot's open-source model Kimi K2.5, with large-scale improvements via reinforcement learning (RL). It is said to have strengthened long-running tasks, following complex instructions, and natural collaboration through targeted textual feedback and a 25x scaling of synthetic tasks. It shows high scores on benchmarks such as CursorBench and is rated as delivering performance equal to or better than Claude Opus 4.7/4.8 or GPT-5.5 at a lower cost. Cursor official