dsh-video-preview

DSH Video Preview

Play workspace videos directly in DeepSeek Harness's right-side context / document preview panel. Instead of showing "unsupported file type", the panel renders a native video player with working seeking, including files larger than the 32 MiB RPC preview read limit.

• Package: @lifenrir/dsh-video-preview
• DSH: >= 0.2.1-rc.2
• Node: ^22.19 || >=24

Features

• Inline `` inside the right-side document panel: play, pause, seek, and fullscreen.
• Authenticated Host route /api/dsh-video-preview/stream that implements HTTP Range (206 / 416), so seeking is not limited by the RPC preview cap.
• 4 MiB chunked reads through ctx.fs.readByteRange; a HEAD probe validates the path, MIME type, and workspace permission before the browser issues its GET.
• Only known video extensions are accepted; everything else returns 415.
• The player follows the DSH theme through --dsw-alias-* design tokens.

Supported containers and codecs

Extension · Content-Type .mp4, .m4v · video/mp4 .mov · video/quicktime .webm · video/webm .ogv, .ogg · video/ogg .mkv · video/x-matroska

Container recognition does not imply codec support. The browser still has to decode the stream:

• H.264/AAC in MP4 and VP8/VP9 in WebM have the widest compatibility.
• .mov often contains ProRes, and .mkv often contains H.265/AC-3 or other codecs browsers do not ship decoders for. When decoding fails the panel shows "This browser cannot play this video format" with a Retry button.

Install

From npm

dsh plugin add @lifenrir/dsh-video-preview

From a local directory

git clone https://github.com/LiFenrir/dsh-video-preview.git
dsh plugin add /absolute/path/to/dsh-video-preview

No build step is required: the Host half is the ESM entry index.js, and the browser half is client.js, loaded through window.__ModuleLoader__.

From git

dsh plugin add git+https://github.com/LiFenrir/dsh-video-preview.git

Reload the Web UI (or restart the profile) after adding and enabling the plugin.

Usage

1. Open a workspace video from the Files tab.
2. The right-side preview panel shows the player.
3. Use the native controls to play, seek, and enter fullscreen.

How it works

• index.js registers the streaming route on the authenticated connection layer via ctx.connection.fetch.register.
• The route resolves the session workspace through the workspaceFileScope lookup, then resolves and stats the requested path with ctx.fs, which keeps sandbox rules in force.
• client.js registers a document-preview definition for the supported extensions and the panel component. It parses the dsh-resource://file/session// address, performs the HEAD probe, and only then points the `` element at the stream URL.

Security

• The stream route is served through DSH's authenticated connection layer; paths are resolved relative to the session's workspace root and remain subject to the ctx.fs sandbox.
• Responses use Cache-Control: private, no-store and X-Content-Type-Options: nosniff.
• Error responses do not leak internal error details.
• Request paths containing NUL bytes are rejected, and only the extensions listed above are served.

Verify

1. Enable the plugin and reload the Web UI.
2. Open a .mp4 file from the Files tab.
3. The right-side preview should show a player, and dragging the progress bar should seek correctly.
4. Optionally open a file larger than 32 MiB and confirm that seeking still works.

If the panel reports a load failure, check that the file exists, lies inside the current session workspace, and has a supported extension. If it reports an unsupported format, the container may be recognized but the codec is not decodable by the browser.

Development

This package has no build step and no runtime dependencies. The source files are the shipped files:

index.js            Host half (stream route)
client.js           Browser half (document preview + player)
cordis.patch.yml    Bundle manifest
locale/{en,zh}.json Display metadata
icon.svg            Plugin icon

To test a change locally, point dsh plugin add at this directory and reload the Web UI.

License

MIT. See LICENSE.