Canvas Panel: Agent-Controlled WKWebView Workspace for macOS

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

Where Canvas lives

Canvas state is kept in Application Support:

• ~/Library/Application Support/OpenClaw/canvas/<session>/...

The Canvas panel serves these files through 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

When no index.html exists at the root, the app displays a built-in scaffold page.

Panel behavior

• A borderless, resizable panel anchored near the menu bar or mouse cursor.
• Opening Canvas does not switch apps or take keyboard focus.
• Size and position are remembered per session.
• Automatically reloads when local canvas files change.
• Only one Canvas panel is visible at a time, with session switching as needed.

Canvas can be turned off from Settings -> Allow Canvas. When disabled, canvas node commands return CANVAS_DISABLED.

Agent API surface

Canvas is available through the Gateway WebSocket, letting the agent show or hide the panel, navigate to a path or URL, run JavaScript, and capture a snapshot image:

openclaw nodes canvas present --node <id>
openclaw nodes canvas navigate --node <id> "/"
openclaw nodes canvas eval --node <id> --js "document.title"
openclaw nodes canvas snapshot --node <id>

eval and a2ui.* update content without opening or revealing the panel. Only present, navigate, or a user action shows it. After hiding, content updates continue to apply to the hidden panel. snapshot requires a visible panel and returns CANVAS_HIDDEN otherwise. Run present first.

canvas.navigate accepts local canvas paths, http(s) URLs, and file:// URLs. Passing "/" shows the local scaffold or index.html.

Gateway-hosted targets under /__openclaw__/canvas/ and /__openclaw__/a2ui/ are resolved through the node session's current scoped Canvas URL. The app refreshes that short-lived capability before navigation, so you do not need to construct or copy a capability URL yourself.

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 automatically navigates to the A2UI host page on first open.

The advertised URL is capability-scoped, for example http://<gateway-host>:18789/__openclaw__/cap/<token>/__openclaw__/a2ui/?platform=macos. Treat it as ephemeral credentials, not a stable link.

A2UI commands (v0.8)

Canvas supports A2UI v0.8 server-to-client messages: beginRendering, surfaceUpdate, dataModelUpdate, deleteSurface. createSurface (v0.9) is not yet supported.

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"

Triggering agent runs from Canvas

Canvas can start new agent runs using openclaw://agent?... deep links:

window.location.href = "openclaw://agent?message=Review%20this%20design";

Supported query parameters:

The app asks 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.

Security notes

• The Canvas scheme blocks directory traversal. Files must reside 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.
• Ordinary web pages are render-only. Agent actions are accepted only from the app-owned Canvas scheme or the exact capability-scoped Gateway A2UI document selected by the app. Subframes, redirects, stale capabilities, and changed queries cannot dispatch actions.

Related

• macOS app
• WebChat