Willison uses Claude to port Mermaid ASCII converter to WebAssembly
Source published ·Modelwire updated
Original coverage: Simon Willison ↗·How Modelwire adds context
The development
Simon Willison has expanded his Mermaid diagram conversion toolkit by compiling an older Go library into WebAssembly using Claude Fable 5, enabling browser-based rendering with color support. This represents a practical workflow for converting LLM-friendly diagram syntax into terminal-compatible ASCII art, addressing a gap between modern diagramming tools and legacy systems. The move signals how AI-assisted compilation is enabling developers to resurrect and adapt older codebases for contemporary web environments, particularly useful for teams bridging visual design and infrastructure automation.
Modelwire’s AI-generated summary of coverage from Simon Willison.
Modelwire analysis
ExplainerOur AI-generated reading of the wider context and the next developments to watch.
The real story here is not the ASCII output itself but the method: Willison used Claude Fable 5 to handle the Go-to-WebAssembly compilation, which means the AI was doing build engineering work rather than generating new code from scratch. That distinction matters because it points to a use case where LLMs act as porting assistants for existing, unmaintained libraries rather than as authors.
This is largely disconnected from recent activity in our archive, as we have no prior coverage to anchor it to. It belongs to a broader pattern of developers using AI assistance to extend the lifespan of older open-source code, particularly by targeting WebAssembly as a distribution target that sidesteps dependency and runtime concerns. The AlexanderGrooff/mermaid-ascii library being the source material is worth noting: it was not written for the web, and getting it there required someone (or something) to absorb the porting friction.
Watch whether Willison or others in the Mermaid tooling community publish similar Go-to-WASM ports of other diagram utilities in the next few months. If that pattern repeats across multiple unmaintained libraries, it would suggest AI-assisted compilation is becoming a reliable enough workflow to treat as a standard technique rather than a one-off experiment.
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MentionsSimon Willison · Claude Fable 5 · Mermaid · AlexanderGrooff/mermaid-ascii · WebAssembly · Grok Build
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Modelwire summarizes, we don’t republish. Simon Willison originally reported this story as “Mermaid to ASCII art (mermaid-ascii)”. The full content lives on simonwillison.net. If you’re a publisher and want a different summarization policy for your work, see our takedown page.