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The macOS app embeds an agent-controlled Canvas panel using WKWebView, a lightweight visual workspace for HTML/CSS/JS, A2UI, and small interactive UI surfaces.

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Where Canvas lives

Canvas state is stored under Application Support:
  • ~/Library/Application Support/OpenClaw/canvas/<session>/...
The Canvas panel serves those files via a custom URL scheme, openclaw-canvas://<session>/<path>:
  • openclaw-canvas://main/ -> <canvasRoot>/main/index.html
  • openclaw-canvas://main/assets/app.css -> <canvasRoot>/main/assets/app.css
  • openclaw-canvas://main/widgets/todo/ -> <canvasRoot>/main/widgets/todo/index.html
If no index.html exists at the root, the app shows a built-in scaffold page.

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Panel behavior

  • Borderless, resizable panel anchored near the menu bar (or mouse cursor).
  • Remembers size/position per session.
  • Auto-reloads when local canvas files change.
  • Only one Canvas panel is visible at a time (session switches as needed).
Canvas can be disabled from Settings -> Allow Canvas. When disabled, canvas node commands return CANVAS_DISABLED.

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Agent API surface

Canvas is exposed via the Gateway WebSocket, so the agent can show/hide the panel, navigate to a path or URL, evaluate JavaScript, and capture a snapshot image: 
openclaw nodes canvas present --node <id>
openclaw nodes canvas navigate --node <id> --url "/"
openclaw nodes canvas eval --node <id> --js "document.title"
openclaw nodes canvas snapshot --node <id>
canvas.navigate accepts local canvas paths, http(s) URLs, and file:// URLs. Passing "/" shows the local scaffold or index.html.

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A2UI in Canvas

A2UI is hosted by the Gateway canvas host and rendered inside the Canvas panel. When the Gateway advertises a Canvas host, the macOS app auto-navigates to the A2UI host page on first open. Default A2UI host URL: http://<gateway-host>:18789/__openclaw__/a2ui/

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A2UI commands (v0.8)

Canvas accepts A2UI v0.8 server-to-client messages: beginRendering, surfaceUpdate, dataModelUpdate, deleteSurface. createSurface (v0.9) is not supported yet. 
cat > /tmp/a2ui-v0.8.jsonl <<'EOFA2'
{"surfaceUpdate":{"surfaceId":"main","components":[{"id":"root","component":{"Column":{"children":{"explicitList":["title","content"]}}}},{"id":"title","component":{"Text":{"text":{"literalString":"Canvas (A2UI v0.8)"},"usageHint":"h1"}}},{"id":"content","component":{"Text":{"text":{"literalString":"If you can read this, A2UI push works."},"usageHint":"body"}}}]}}
{"beginRendering":{"surfaceId":"main","root":"root"}}
EOFA2

openclaw nodes canvas a2ui push --jsonl /tmp/a2ui-v0.8.jsonl --node <id>
Quick smoke test: 
openclaw nodes canvas a2ui push --node <id> --text "Hello from A2UI"

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Triggering agent runs from Canvas

Canvas can trigger new agent runs via openclaw://agent?... deep links: 
window.location.href = "openclaw://agent?message=Review%20this%20design";
Supported query parameters:
ParameterMeaning
messagePrefilled agent prompt.
sessionKeyStable session identifier.
thinkingOptional thinking profile.
deliver, to, channelDelivery target.
timeoutSecondsOptional run timeout.
keyApp-generated safety token for trusted local callers.
The app prompts for confirmation unless a valid key is provided. Unkeyed links show the message and URL before approval, and ignore delivery routing fields; keyed links use the normal Gateway run path.

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Security notes

  • Canvas scheme blocks directory traversal; files must live under the session root.
  • Local Canvas content uses a custom scheme (no loopback server required).
  • External http(s) URLs are allowed only when explicitly navigated.