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Technical reference

Rich output protocol

Assistant output carries delivery/render directives through a few dedicated channels:

  • Structured mediaUrl / mediaUrls fields for attachment delivery.
  • [[audio_as_voice]] for audio presentation hints.
  • [[reply_to_current]] / [[reply_to:<id>]] for reply metadata.
  • [embed ...] for Control UI rich rendering.

Structured media fields and [[...]] tags are delivery metadata. [embed ...] is the separate web-only rich-render path; it is not a media alias.

Media attachments

Remote attachments must be public https: URLs. http:, loopback, link-local, private, and internal hostnames are rejected as attachment directives; server-side media fetchers apply their own network guards on top.

Local attachments accept absolute paths, workspace-relative paths, or home-relative ~/ paths. They still pass the agent file-read policy and media type checks before delivery.

Plain Markdown image syntax (![alt](url)) stays text by default. Channels that want Markdown images treated as media replies opt in at their outbound adapter; Telegram does this so ![alt](url) becomes a media attachment.

When block streaming is enabled, media must ride on structured payload fields. If the same media URL appears in a streamed block and again in the final assistant payload, OpenClaw delivers it once and strips the duplicate from the final payload.

[embed ...]

[embed ...] is the only agent-facing rich-render syntax for the Control UI. Self-closing example:

text
[embed ref="cv_123" title="Status" /]

Rules:

  • [view ...] is no longer valid for new output.
  • Embed shortcodes render only in the assistant message surface.
  • Only URL-backed embeds render; use ref="..." or url="...".
  • Block-form inline HTML embed shortcodes do not render.
  • The web UI strips the shortcode from visible text and renders the embed inline.

Stored rendering shape

The normalized/stored assistant content block is a structured canvas item:

json
{  "type": "canvas",  "preview": {    "kind": "canvas",    "surface": "assistant_message",    "render": "url",    "viewId": "cv_123",    "url": "/__openclaw__/canvas/documents/cv_123/index.html",    "title": "Status",    "preferredHeight": 320  }}

present_view is not recognized; stored/rendered rich blocks always use this canvas shape.

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