Viaduct
Viaduct is a free C4 modeling tool for software teams, with a hosted MCP server that feeds your…
FreeCodeVisual editingMCP1,834 impressions#8 of its week7 comments
Comments
>log in to comment- Brandon Pickert· 11d ago
Congrats on shipping this one.
- Brandon Pickert· 11d ago
Congrats on shipping this one.
- kris gu· 15d ago
把 C4 四层图和托管 MCP 打通这个点很对我胃口，平时架构图最容易烂尾就是画完没人维护，代码一改图就过期。想问下 change set 是只记录模型自己的改动，还是能对照代码变更提示哪些容器、组件关系已经对不上了？
Yes, change sets work in both directions. For example, when you add elements or make changes to a diagram, the change set tells the agent exactly what needs to change in the code. You can also enable an instruction for the agent to update the documentation after completing its work, so it reflects what was actually implemented. The goal is to help the agent develop with the full architectural context available through Viaduct’s MCP integration, while also keeping the documentation up to date.
- Aditya Goel· 17d ago
Sharing a C4 model with AI coding tools over MCP is a fresh angle for architecture docs. Is the MCP piece what gets teams to try it, or the free modeling? Search note: I googled "c4 model diagram tool" (Google, US settings). The official C4 site takes two spots, plus a C4 tools directory, an r/softwarearchitecture thread, Structurizr, Visual Paradigm, a LinkedIn list and draw.io. Viaduct isn't there yet; the official site's tooling page and that tools directory both list tools, so they're worth asking about. I run AI Knows Us, so this kind of search check is what I do.
Viaduct is: - Main C4 site: https://c4model.com/tooling - Wiki: https://en.wikipedia.org/wiki/C4_model
We 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?
More Code tools →74 free dev tools →
Looking for MCP servers to install? MCP servers list: 289 servers by category, official and community →
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 | 9 | 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.
