archpane

A live architecture diagram in a side pane of Claude Code. Ask Claude to diagram a system and it draws it next to the chat, then keeps it current while you talk.

What it does

• Claude draws the diagram, you keep talking. "Diagram how checkout works", then "add a fraud check before payment". The pane updates in place.
• Big systems become subdiagrams. A box marked ▸ opens a diagram of what happens inside it when you click it, and a breadcrumb leads back.
• Ask about any component. Click a box to put [diagram <name>: <id>] in your prompt, then type your question.
• Track a build. Components are planned, building, done or blocked, shown by color, and Claude updates them as the work lands.
• Explore it with the mouse. Hover for details, right-click for a menu, drag to pan.

Requirements

• Claude Code 2.1.288 or newer. archpane is a Claude Code mod, and mods are an early-access feature whose API can change.
• A terminal that passes mouse events to Claude Code. Tested in Ghostty; reports from other terminals are welcome.
• For the docked pane: Claude Code's fullscreen layout, at least 110 columns wide. Narrower than that, it shows inline above the prompt.

Install

/plugin marketplace add facumarcet/archpane
/plugin install archpane@archpane

Restart Claude Code once if /diagram doesn't appear. To skip the permission prompt the first time Claude draws, add "mcp__archpane__diagram" to permissions.allow in ~/.claude/settings.json.

Use

/diagram              open the pane on this project's last diagram (or "main")
/diagram payments     switch to, or create, the diagram named "payments"
/diagram list         list this project's diagrams

Then ask Claude, for example: "diagram the services in this repo and how they talk to each other", or "we're about to build X: put the plan in the diagram and update it as we go".

How it works

A bundled skill teaches Claude to draw diagrams that read well in a narrow pane. After every edit, the tool tells Claude whether the diagram fits and what to fix if it doesn't. A diagram is plain JSON: nodes { id, label, kind, group, status, note, detail } and edges { from, to, label }.

Diagrams are saved on your machine, in Claude Code's plugin store, keyed by the directory Claude Code was started in. Nothing is written to your repository.

Details for contributors: docs/ARCHITECTURE.md.

Troubleshooting

• The pane opens inline instead of beside the chat. Use the fullscreen layout and widen the terminal to 110 columns or more.
• Clicks do nothing. Your terminal has to pass mouse events to Claude Code. tmux isn't tested; try outside it first.
• A dim archpane: … error line appears after an update. Run /diagram once to redraw. If it persists, please open an issue.

Limits

• Diagrams can't be shared with teammates yet, since they live on your machine.
• If two sessions edit the same diagram at once, the last save wins.
• Boxes can't be moved by hand yet.
• A diagram holds at most 100 components and 200 edges. Claude is told to split anything bigger.

Update and uninstall

/plugin marketplace update archpane
/plugin update archpane@archpane
/plugin uninstall archpane@archpane

Development

git clone https://github.com/facumarcet/archpane.git
claude --plugin-dir ./archpane/plugins/archpane   # hot-reloads on every edit
claude plugin test ./archpane/plugins/archpane

License

MIT