Canvas Skill

Display HTML content on connected i-clavdivs nodes (Mac app, iOS, Android).

Overview

The canvas tool lets you present web content on any connected node's canvas view. Great for:

•Displaying games, visualizations, dashboards
•Showing generated HTML content
•Interactive demos

How It Works

Architecture

code

┌─────────────────┐     ┌──────────────────┐     ┌─────────────┐
│  Canvas Host    │────▶│   Node Bridge    │────▶│  Node App   │
│  (HTTP Server)  │     │  (TCP Server)    │     │ (Mac/iOS/   │
│  Port 18793     │     │  Port 18790      │     │  Android)   │
└─────────────────┘     └──────────────────┘     └─────────────┘

•Canvas Host Server: Serves static HTML/CSS/JS files from canvasHost.root directory
•Node Bridge: Communicates canvas URLs to connected nodes
•Node Apps: Render the content in a WebView

Tailscale Integration

The canvas host server binds based on gateway.bind setting:

Bind Mode	Server Binds To	Canvas URL Uses
`loopback`	127.0.0.1	localhost (local only)
`lan`	LAN interface	LAN IP address
`tailnet`	Tailscale interface	Tailscale hostname
`auto`	Best available	Tailscale > LAN > loopback

Key insight: The canvasHostHostForBridge is derived from bridgeHost. When bound to Tailscale, nodes receive URLs like:

code

http://<tailscale-hostname>:18793/__i-clavdivs__/canvas/<file>.html

This is why localhost URLs don't work - the node receives the Tailscale hostname from the bridge!

Actions

Action	Description
`present`	Show canvas with optional target URL
`hide`	Hide the canvas
`navigate`	Navigate to a new URL
`eval`	Execute JavaScript in the canvas
`snapshot`	Capture screenshot of canvas

Configuration

In ~/.i-clavdivs/i-clavdivs.json:

json

{
    "canvasHost": {
        "enabled": true,
        "port": 18793,
        "root": "/Users/you/clawd/canvas",
        "liveReload": true
    },
    "gateway": {
        "bind": "auto"
    }
}

Live Reload

When liveReload: true (default), the canvas host:

•Watches the root directory for changes (via chokidar)
•Injects a WebSocket client into HTML files
•Automatically reloads connected canvases when files change

Great for development!

Workflow

1. Create HTML content

Place files in the canvas root directory (default ~/clawd/canvas/):

bash

cat > ~/clawd/canvas/my-game.html << 'HTML'
<!DOCTYPE html>
<html>
<head><title>My Game</title></head>
<body>
  <h1>Hello Canvas!</h1>
</body>
</html>
HTML

2. Find your canvas host URL

Check how your gateway is bound:

bash

cat ~/.i-clavdivs/i-clavdivs.json | jq '.gateway.bind'

Then construct the URL:

•loopback: http://127.0.0.1:18793/__i-clavdivs__/canvas/<file>.html
•lan/tailnet/auto: http://<hostname>:18793/__i-clavdivs__/canvas/<file>.html

Find your Tailscale hostname:

bash

tailscale status --json | jq -r '.Self.DNSName' | sed 's/\.$//'

3. Find connected nodes

bash

i-clavdivs nodes list

Look for Mac/iOS/Android nodes with canvas capability.

4. Present content

code

canvas action:present node:<node-id> target:<full-url>

Example:

code

canvas action:present node:mac-63599bc4-b54d-4392-9048-b97abd58343a target:http://peters-mac-studio-1.sheep-coho.ts.net:18793/__i-clavdivs__/canvas/snake.html

5. Navigate, snapshot, or hide

code

canvas action:navigate node:<node-id> url:<new-url>
canvas action:snapshot node:<node-id>
canvas action:hide node:<node-id>

Debugging

White screen / content not loading

Cause: URL mismatch between server bind and node expectation.

Debug steps:

•Check server bind: cat ~/.i-clavdivs/i-clavdivs.json | jq '.gateway.bind'
•Check what port canvas is on: lsof -i :18793
•Test URL directly: curl http://<hostname>:18793/__i-clavdivs__/canvas/<file>.html

Solution: Use the full hostname matching your bind mode, not localhost.

"node required" error

Always specify node:<node-id> parameter.

"node not connected" error

Node is offline. Use i-clavdivs nodes list to find online nodes.

Content not updating

If live reload isn't working:

•Check liveReload: true in config
•Ensure file is in the canvas root directory
•Check for watcher errors in logs

URL Path Structure

The canvas host serves from /__i-clavdivs__/canvas/ prefix:

code

http://<host>:18793/__i-clavdivs__/canvas/index.html  → ~/clawd/canvas/index.html
http://<host>:18793/__i-clavdivs__/canvas/games/snake.html → ~/clawd/canvas/games/snake.html

The /__i-clavdivs__/canvas/ prefix is defined by CANVAS_HOST_PATH constant.

Tips

•Keep HTML self-contained (inline CSS/JS) for best results
•Use the default index.html as a test page (has bridge diagnostics)
•The canvas persists until you hide it or navigate away
•Live reload makes development fast - just save and it updates!
•A2UI JSON push is WIP - use HTML files for now