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[ARTICLE · art-61315] src=simonwillison.net ↗ pub= topic=developer-tools verified=true sentiment=· neutral

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.

read1 min views1 publishedJul 16, 2026 
**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 I ran in Claude Code for web (Fable 5), and this is what the resulting tool looks like:

source & further reading
simonwillison.net — original article How I tricked Claude into leaking your deepest, darkest secrets simonw/pedalican datasette code-frequency chart on GitHub
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