xAI Open-Sources Grok Build — 844K Lines of Apache-2.0 Rust for a Terminal Coding Agent With Parallel Subagents and Per-Worktree Isolation

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On July 15, 2026 xAI published its terminal-native coding agent Grok Build to GitHub under xai-org/grok-build (Apache 2.0), releasing roughly 844,530 lines of Rust. It delegates large tasks to specialized subagents that run in parallel — each launchable in its own git worktree — and can run fully local-first: compile it yourself, point config.toml at your own local inference. This is a rare full-source drop of a frontier lab's production agent, giving builders a real Rust codebase to study for worktree isolation and subagent orchestration patterns.