Sketchboard Excalidraw

Excalidraw canvas authorship + headless-render MCP server. Slots next to inkscape-mcp and gimp-mcp as the vector/raster/diagram trio in the fleet.

Status: day 1 scaffold. Server shell, package layout, and fleet standardization are in place. Canvas bridging, headless rendering, Mermaid conversion, and batch rendering are registered as MCP tools but return not_implemented - see docs/DESIGN.md for what's real vs planned.

What this is

A merge of two upstream approaches into one fleet-standard server:

• Canvas workbench (base: forked from lesleslie/excalidraw-mcp, itself built on yctimlin/mcp_excalidraw): Python FastMCP server + TypeScript canvas server + React frontend for live, interactive diagram authorship.
• Headless rendering (approach borrowed from bassimeledath/excalidraw-render-mcp, reimplemented in Python/Playwright rather than vendoring a second Node stack): a warm Chromium instance rendering Excalidraw element JSON to SVG/PNG via exportToSvg/exportToBlob, with the excalidraw JS bundle vendored locally instead of loaded from a CDN.

The two modes are deliberately decoupled: headless render tools work without the canvas server running (agent batch mode), while the canvas/Tauri app is for interactive human use. Both talk to the same backend; the desktop app is not a sidecar wrapping the Python server.

Fork sources on this machine

Both upstream forks were cloned for reference/cherry-picking, not vendored wholesale:

• D:\Dev\repos\external\excalidraw-mcp-lesleslie\
• D:\Dev\repos\external\excalidraw-render-bassimeledath\

Planned extras

• Mermaid-to-Excalidraw conversion, wrapping the official @excalidraw/mermaid-to-excalidraw npm package rather than reimplementing Mermaid parsing.
• .excalidrawlib support for reusable fleet-diagram components (server boxes, transport arrows).
• Batch-render command for the repo-README diagram pipeline across the fleet (~200 repos).

Ports

Port	Service
11107	Backend (FastMCP HTTP /mcp + REST)
11108	Frontend (Vite React canvas)

Registered in mcp-central-docs/operations/WEBAPP_PORTS.md.

License and attribution

MIT, same as both upstream sources. Credit chain: this project builds on lesleslie/excalidraw-mcp (which credits yctimlin/mcp_excalidraw) and borrows the headless-render architecture from bassimeledath/excalidraw-render-mcp. Font licensing (Excalidraw's default hand-drawn fonts ship under SIL OFL, not MIT) is tracked separately in NOTICE.md once the JS bundle is vendored.

Development

uv sync
uv run pytest
just release-dry

See docs/DESIGN.md for the day 1/2/3 build plan and the concrete technical decisions behind this scaffold.