LiamPrevelige

Hey HN, we’re Will and Liam, founders of CodeViz (YC S24). We’re building a VS Code extension that reads your code and generates editable architecture diagrams (C4, UML). It’s mostly used by teams to build shared context, agree on technical decisions, and visualize PRs.

Here’s a recorded demo: https://youtu.be/Jh3wkrCj_WQ You can try the VS Code extension here: https://marketplace.visualstudio.com/items?itemName=CodeViz....

It’s free for 10 generations/month (no signup). Then, we have a $19/month plan for unlimited diagram generation and $50/month plan for live collaboration.

We launched a v1 last year to help engineers read code faster (https://news.ycombinator.com/item?id=41393458), but no one actually used CodeViz for that. Users were taking screenshots of our diagrams for presentations and architecture reviews. We rebuilt CodeViz to shift from a passive viewer to a collaborative editor for modeling specific flows, using C4 and UML standards.

This required a major change in our technical approach. In our original version, we relied on static analysis, building stack graphs with tree-sitter for ~15 languages (using language servers as teachers). While technically precise, these graphs were way too noisy and didn’t map to human abstractions.

We now use an adaptation of gemini-cli to read the codebase, generate C4 + Activity PlantUML diagrams, and link nodes directly to source code. These are parsed into a diagram editor that we built with ReactFlow. You can click to expand nodes into lower levels of abstraction, ask an AI assistant to visualize a specific flow, or import PRs from GitHub.

CodeViz is in active development, all honest feedback is much appreciated! Our roadmap is largely focused on tools for working in teams, so we’d also love to hear about your problems with architecture reviews and onboarding.

Hey HN — we’re Liam and Will from CodeViz (https://codeviz.ai). We're building a VS Code extension that generates interactive diagrams of codebases, from system architecture down to function call graphs. Here’s a demo where we analyze OpenHands, uv, and webviz: https://www.youtube.com/watch?v=fgfDXUtWzRk.

The extension is public if you want to try it on your own repos: https://marketplace.visualstudio.com/items?itemName=CodeViz....

Will and I started CodeViz because we wanted more intuitive representations of software. During our time at Tesla, we encountered a common problem: software engineers spend very little time actually typing code. Most development time was spent navigating convoluted files and building a mental map for each task. At the same time, whiteboard sessions were proof that code could be expressed intuitively.

We started with autogenerated technical documentation. Of course, long markdown docs are not a good solution for long files of code. We realized we needed diagrams that (a) help grasp large quantities of code and (b) can be filtered according to the developer’s task. So, we built a graph-based VS Code extension. It generates diagrams directly within VS Code, illustrating connections between functions and providing overviews of system architecture. These visualizations update as code changes.

CodeViz appears as a side panel in VS Code with two views:

(1) Call graph: as you click on functions, we show a chain of upstream and downstream references. You can navigate your codebase using the call stack and see, in one view, everywhere your functions are called. We generate this call graph using the language servers developers have already installed in VS Code

(2) Architecture diagram: we create a C4 diagram of your system, so you can see a top-level view of your codebase and click into the component layer. We were surprised to find that a small fraction of code can generate a very accurate representation of the system. We detect these important files, then use LLMs to build nested architecture diagrams at the container and component level

Developers are mainly using our extension to navigate spaghetti code, onboard new devs, and interpret open source repos. We're still figuring out our pricing. Currently, we offer basic features for free, with a paid tier for more resource-intensive tools like detailed architecture diagrams. Open to suggestions on this approach.

CodeViz is in active development and our main focus over the next couple of days is to make the call graph much easier to view and navigate. We're continuously working to make it better, so your honest feedback, suggestions, and wishes would be very helpful. Looking forward to hearing any and all thoughts, whether about the current extension, general problem space, or something else!