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.