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OpenClaw chat clients play assistant audio and video attachments inline. The Gateway keeps those attachments behind session-scoped access, serves seekable byte ranges, and can prepare a portable playback rendition for recognized formats that are not safe across every client. This page covers playback in OpenClaw clients. Channel delivery, inbound media understanding, and live voice conversations use separate paths; see Image and media support, Media understanding, and Talk mode.

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Client support

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Portable formats

The Gateway classifies these formats as the portable native set shared by the browser, Apple players, and Android Media3: The Linux companion can also play formats supplied by its installed GStreamer plugins. Browser and operating-system updates may add native formats, but the table above is the cross-client contract OpenClaw targets.

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Lazy playback renditions

Both Gateway byte routes accept ?playback=1: the managed attachment route under /api/chat/media/outgoing/.../full and the Control UI assistant-media route. Attachment metadata can report playback: "native" or playback: "transcode" so a client can choose the rendition deliberately. Playback conversion is lazy:
  1. A native source passes through unchanged.
  2. A recognized non-portable source starts a bounded ffmpeg job. The route returns HTTP 202 with { "status": "preparing" } while the rendition is being prepared.
  3. A later request receives the cached M4A or MP4 rendition.
  4. If inspection or conversion is unavailable, fails, or exceeds a limit, the route falls back to the original bytes. The client can then show its unplayable-media fallback and keep the download action available.
Transcoding accepts sources up to 20 minutes and never raises the normal audio or video byte cap. Cached playback renditions are pruned by normal media-store maintenance.

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Managed attachments and access

Agent-produced audio and video are stored as managed media artifacts. Images keep their separate managed-image artifact family. Native clients resolve the artifact through artifacts.download, which returns inline base64 bytes when the artifact is byte-backed or a short-lived, ticketed URL when it is Gateway-managed. The ticketed byte routes support:
  • Range requests with HTTP 206 Partial Content for seeking
  • ETag and If-Range for safe resume behavior
  • HEAD requests with the same content metadata and no response body
Do not copy a ticketed URL into durable configuration. Clients reacquire a ticket from the authenticated Gateway when needed.

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Metadata and limits

Chat attachments may include sizeBytes, durationMs, width, and height. OpenClaw also uses ffprobe, when available, to fill audio duration and video duration/dimensions for media facts and the Control UI ?meta=1 availability probe. Probing is best-effort: a missing or failed probe leaves fields absent instead of rejecting the attachment. Gateway-managed assistant attachments use these per-file caps: These are playback/storage caps, not the separate media-understanding limits. For transcription and description limits, see Image and media support.

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Troubleshooting

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Duration or dimensions are missing

Check that ffprobe is installed on the Gateway host and visible on its PATH:
Playback of an already portable file can still work without metadata.

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A recognized format downloads instead of playing

Check both media tools on the Gateway host:
ffprobe classifies codecs and duration; ffmpeg creates the portable rendition. If either step cannot safely handle the source, OpenClaw serves the original file and the client keeps its fallback/download path.

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Playback stays in preparing state

The first rendition request is asynchronous. Wait briefly and retry. Very large, longer than 20-minute, unprobeable, or unsupported sources remain on the original-byte fallback instead of blocking the Gateway.

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Linux reports a codec error

Use the package and source-build instructions in Linux media codecs. The .deb depends on the required GStreamer plugin packages; the AppImage carries the media framework and codecs installed by the release build.

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Android shows a media row while offline

That is expected. Android caches the transcript metadata, not the attachment bytes or its short-lived download capability. Reconnect, then play again so the app can request a new ticket.