Grok Build

Grok Build (grok) is xAI's open-source terminal-based AI coding agent, written entirely in Rust. It is a periodic snapshot from xAI's internal monorepo — source is published but external contributions are not accepted.

The codebase is a Rust workspace spanning ~80 crates and well over 1M lines. The largest crates are the TUI pager (425K lines), the agent shell/runtime (338K lines), the tools crate (112K lines), and the workspace crate (78K lines). It runs as a full-screen TUI, headlessly for scripting/CI, or embedded in editors via the Agent Client Protocol (ACP).

Architecturally, the system is built around a Tool trait as its central abstraction — every tool implements a streaming execute method that emits zero or more Progress items followed by exactly one Terminal result. Tools are registered in a ToolBridge central registry. Agents are assembled via a 10-step AgentBuilder fluent API, supporting allowlist/denylist resolution, compat tool-name mapping (Claude's "Read/Bash/Grep/Edit" → Grok's ToolKind), MCP tool integration, and skill discovery.

Key subsystems include: a transport-agnostic compaction engine with three strategies (full-replace for coding agents, tail-keep and between-turn for chat), an actor-based conversation state manager (ChatStateActor), a markdown- plus-SQLite-vector memory system, a tree-sitter codebase graph with go-to- definition and references, and a multi-layer config system supporting Ed25519-signed enterprise policy. The hook system discovers JSON-defined hooks from ~/.grok/hooks/ and executes them as child processes at session/tool lifecycle events.

Notable design choices: TUI-first (unlike most coding agents which are CLI- first), pure Rust end-to-end (avoiding GC pauses and enabling single-binary distribution), a dedicated compaction model, and vendored Rust implementations of Mermaid diagram parsing, layout, and SVG rendering — eliminating the Node.js dependency common to other agents.