xAI Open-Sources Grok CLI With a Reusable Mermaid Renderer

xAI open-sourced Grok CLI on July 16, making it the fourth major-lab terminal coding agent now in the open, per Simon Willison.

Willison's post frames that as the bigger point: Grok CLI's arrival brings the count of open-source, major-lab terminal coding agents to four.

The specific find is a file: xai-grok-markdown/src/mermaid.rs. It's a self-contained Rust module that renders Mermaid diagrams as Unicode box art directly in the terminal.

Willison says the module is liftable on its own. A developer building a different TUI wouldn't need the rest of Grok CLI, just this file, to get diagram rendering working. For anyone shipping a terminal tool, that's one rendering problem already solved.

The mermaid.rs file will probably get copied into more terminal projects than anyone builds directly on top of Grok CLI itself. A tight, dependency-free utility travels faster than a full coding agent stamped with someone else's opinions. That's the kind of file that outlives the project it shipped in.