Viaduct
Viaduct is a free C4 modeling tool for software teams, with a hosted MCP server that feeds your…
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>log in to commentWe built Viaduct to give software teams a free, collaborative C4 modeling tool that also streams the architecture to AI agents via a hosted MCP server. It supports system, container, component and code diagrams, live teamwork, and generates change sets for coding agents. How do you currently keep architecture diagrams in sync with your codebase?
Viaduct is a free C4 modeling tool that lets software teams create, share, and sync architecture models with AI agents via a hosted MCP server.
- for
- Software teams that need collaborative architecture modeling and AI-assisted documentation.
- pricing
- freemium · free trial
Key features
- Full C4 modeling — Create system context, container, component and code diagrams in one editor.
- Hosted MCP server — Provides a machine-readable context for AI agents to read and write architecture data.
- Live collaboration — Team projects with change sets and real-time sharing.
- AI assistant — Generates missing descriptions, names, and reviews model elements for you.
- Desktop app — Native app with local MCP server, offline work and JSON file storage.
- Import/Export — Import OpenAPI specs and export models or contracts as JSON or OpenAPI.
Use cases
- Synchronize architecture diagrams across team members and AI agents.
- Generate missing documentation automatically with the built-in AI assistant.
- Export contracts as OpenAPI for downstream code generation.
- Run the desktop app offline for secure, on-premise architecture work.
- Track and apply change sets to keep model and code in sync.
Viaduct pricing
- Browser (free)€0All four C4 levels · Hosted MCP server · Team projects · Change sets
- Desktop licence€10/month7-day free trial · Runs locally on macOS, Windows, Linux · One licence covers 3 machines · Works offline
Viaduct vs alternatives
 Viaduct |  Mintlify |  Outline |  Gitea | ||
|---|---|---|---|---|---|
| Best for | C4 architecture modeling with AI integration | Developer documentation platform | Open-source docs sites | Fast team knowledge base | Self-hosted Git hosting |
| Pricing | Freemium | Subscription | Free | Free | Free |
| DevHunt upvotes | 1 | 0 | 0 | 0 | 0 |
| Launched | Oct 2026 | — | — | — | — |
- Viaduct vs Mintlify: Focuses on documentation generation, not C4 architecture modeling
- Viaduct vs Docusaurus: Static site generator for docs, no AI-driven model or MCP server
- Viaduct vs Outline: Team knowledge base wiki, not visual C4 modeling with AI
- Viaduct vs Gitea: Self-hosted Git service, unrelated to architecture modeling
Viaduct FAQ
What does Viaduct cost?+
The browser version is free with an account; the desktop app is free for 7 days then €10 per month.
Do I need an account?+
Yes, a free account is required to save projects, use collaboration, and access the hosted MCP server.
Where is my architecture stored?+
In the cloud on EU servers with backups, or locally as JSON files when using the desktop app.
What can the AI assistant do?+
It writes missing model descriptions, names flow steps, and reviews the model, providing suggestions that you can apply manually.
How does the desktop app differ from the browser version?+
The desktop app runs locally with its own MCP server, stores projects as local JSON files, and works offline; the browser version stores data in the cloud.
Can I import existing specifications?+
Yes, you can import OpenAPI specifications and export models or contracts as JSON or OpenAPI.
Summarized by DevHunt from c4.quietgridlabs.com · Oct 24, 2026. Details may change; check the official site.
