Viaduct
C4 architecture modelling tool that serves your diagrams to coding agents over MCP
Viaduct models a system across the four C4 levels — context, containers, components, code — and keeps docs, sequence diagrams and OpenAPI contracts attached directly to each element instead of in separate tools. A rename or new dependency shows up at every level automatically, and an MCP server lets Cursor or Claude Code query the live model instead of a screenshot pasted into chat. It runs free in the browser with no account, and exports at any time.
What holds up
- +MCP server lets coding agents query the current architecture instead of a stale screenshot
- +Docs and diagrams live on the element itself, so they update instead of rotting in Confluence
- +Free with no account, runs in-browser, and exports any time — no lock-in to try it
Mind the limits
- −Self-hosted MCP server — someone has to run and maintain it
- −No Figma sync mentioned beyond notation; the model is Viaduct's own, not two-way with design tools
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