dsh-video-preview

A video preview for the DeepSeek Harness (DSH) Web UI sidebar. Click an .mp4, .webm or .mov in the file tree, an @ reference, or the workspace-changes list, and it plays in place — instead of "preview is not available for this file type yet".

DSH's built-in document preview registers text, PDF, Excel and images. Video is not one of them. This plugin adds that renderer: mp4 / m4v / webm / ogv / ogg / mov.

中文说明：README.zh.md

Features

• Click and play — suffix-matched renderer that streams the file from an authenticated host route.
• True streaming — the <video> element talks to a byte-range route (206 Partial Content), so seeking is instant and file size has no complete-read cap: a 5 GB video costs only the bytes you actually watch.
• Muted autoplay — browsers refuse audible autoplay, so the preview starts silently; the native controls unmute in one click.
• Useful metadata — filename, container format, size (from a stat route).
• Readable failures — an unsupported codec or container says so instead of showing a blank player.
• Zero runtime dependencies — React comes from the host; everything else is standard Node/browser API. No build step: the browser half is a hand-written __ModuleLoader__ module.
• No host coupling — the browser half registers through the public documentPreviews / slots / locale services; the host half through connection.fetch routes inside the same browser-auth fence as every other /api route.

Install

dsh plugin --profile web add "github:lvxianchao/dsh-video-preview"

main only ever carries released code, so this installs the latest stable release. Then restart dsh (the Web UI reloads its frontend modules on boot):

sudo systemctl restart dsh-web   # adapt to your deployment

The package declares dsh.bundle, so installing it appends the package to the profile's bundle list and mounts the row automatically — no cordis.patch.yml edit needed.

To try it without touching a profile, use an overlay:

dsh --profile web --patch ./dev.yml --host 127.0.0.1 --port 3099 --no-open

# dev.yml
- insert:
    - id: video-preview
      name: '/absolute/path/to/dsh-video-preview/lib/index.js'

Use

1. Type @ in the composer and pick a video file (or open one from the workspace changes).
2. Click the file reference; the right sidebar opens a player and starts muted playback.
3. Drag, unmute, go fullscreen with the native controls. Seeking fetches only the bytes around the new position.

Configuration

Key	Default	Meaning
rangeBytes	2097152 (2 MiB)	Byte window served per stream request. The browser issues consecutive ranges as it plays, so this is a latency/throughput knob, not a size limit.

# ~/.dsh/profiles/web/cordis.patch.yml
- id: video-preview
  config:
    rangeBytes: 4194304   # 4 MiB windows

Limitations

Limit	Cause	Workaround
No mkv	Chrome cannot decode Matroska	Remux to mp4/webm
Codec-dependent	The browser only plays what the platform decodes; HEVC/AV1 vary	H.264/AAC mp4 is the safe choice
Session must resolve	The stream route resolves the file through the session named in the file address	Previewing files from a live session always resolves; a vanished session 404s
Authenticated browsers only	Routes live behind the same auth fence as the rest of /api	That is the point — no unauthenticated file serving

How it works

Half	File	Role
Host	lib/index.js	Registers GET/HEAD /api/video-preview.stream (byte ranges via workspaceFiles.readBytes(range), 206 + Content-Range) and GET /api/video-preview.stat (size/version/type) on connection.fetch
Browser	lib/client.js	Registers the renderer metadata (loading: "renderer") and the keyed document body; renders <video src=…> pointed at the stream route and reports its loaded version

The renderer uses loading: "renderer", so the preview framework never performs a complete-byte read for video files — that is what removes the platform's 32 MB complete-file cap from the video path.

The browser half needs no build step — it is a module in the host loader's own format:

window.__ModuleLoader__.load({ id: "@lvxianchao/dsh-video-preview", factory: (require) => { /* … */ } });

Related

dsh-guard — the same author's password gate for the DSH Web UI: one login, the reverse-proxy /api 403 fix, and the launch-token exchange. This plugin only changes how files preview, not who can open them: if the UI is reachable beyond loopback, put dsh-guard in front of it.

Development

main is the release branch: it only carries code that has been released and tagged. Day-to-day work happens on dev and lands on main when a release is cut.

git checkout dev
# … change, commit, test …
git checkout main && git merge --ff-only dev
git tag -a vX.Y.Z && git push origin main --tags

Shadow instance (isolated DSH_HOME, never touches a live profile or its data):

DSH_HOME=/tmp/dsh-test-home dsh --profile web \
  --patch ./test/shadow.patch.yml --host 127.0.0.1 --port 3199 --no-open

test/shadow.patch.yml mounts the plugin by path. test/e2e.mjs drives headless Chrome through "@ reference → click → assert the <video> plays, serves 206 ranges, and can seek near the end of a file bigger than the old 32 MB cap". test/record-demo.mjs records docs/demo.gif from the same flow (needs puppeteer-core and a Chrome binary).

Sponsor

If this plugin saved you some time, a coffee is welcome:

• ☕ Afdian — mainland China, WeChat / Alipay
• 🌍 Ko-fi — international, PayPal

WeChat tip QR

Changelog

• 1.0.0 — first stable release: streaming byte-range host routes, renderer-owned loading, no complete-file size cap, rangeBytes config.
• 0.1.0 — preview: Blob-based playback of complete bytes (32 MB platform cap applied).

License

MIT