Mermaid to Unicode box art (grok-mermaid)

Developer Simon Willison ported xAI's open-source Rust-based Mermaid diagram renderer to the browser using WebAssembly, creating a tool that converts Mermaid diagrams to Unicode box art. The tool, built from code in the newly open-sourced Grok CLI coding agent, allows terminal-style diagram rendering in web environments.

Tool: Mermaid to Unicode box art grok-mermaid https://tools.simonwillison.net/grok-mermaid While exploring the codebase https://simonwillison.net/2026/Jul/15/grok-build/ for the newly open-sourced Grok CLI coding agent I came across xai-grok-markdown/src/mermaid.rs https://github.com/xai-org/grok-build/blob/b189869b7755d2b482969acf6c92da3ecfeffd36/crates/codegen/xai-grok-markdown/src/mermaid.rs , a "self-contained terminal renderer for Mermaid diagrams" written in Rust. I figured it would be fun to try that out in a browser via WebAssembly. Here's the prompt https://github.com/simonw/tools/pull/293 issue-4897479396 I ran in Claude Code for web Fable 5 , and this is what the resulting tool looks like: