@lcthe/dsh-timeline-rail

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A message timeline rail for the DeepSeek Harness web chat.

Along the left edge of the conversation, above the composer, it draws a low-contrast, evenly spaced column of thin tick marks — one tick per durable user message, styled after a meeting-notes / editor timeline. Hover a tick to preview that message; click it to jump the conversation straight to it.

Desktop & Web both supported. The DeepSeek Harness desktop app is an Electron shell that embeds the same browser client served over a localhost web server, so a "web" plugin renders identically on both. This package targets the browser-side conversation slot and works wherever that client runs — Desktop and Web. Only headless / TUI profiles have no composer slot and render nothing.

Features

• Evenly spaced ticks — one short horizontal line per user message along a 1px track, with a fixed 12px gap; long histories scroll inside the rail instead of compressing the marks.
• Centered marks — each horizontal tick is centered on the vertical rail, keeping the timeline axis visually balanced.
• Complete-history loading — after the session opens, the rail automatically loads earlier history pages in series until no pages remain, and adds ticks as each page arrives.
• Click to jump — aligns the selected user message to the top of the visible message area.
• Hover to preview — a compact wide card shows the user message (#N) in bold, clamped to 2 lines, followed by the assistant reply clamped to 3 lines; image/attachment-only messages get a labelled placeholder.
• Theme aware — colors come from --dsw-* tokens, so it follows the light/dark theme with no extra config.
• Slim and out of the way — pointer-events are none except on the ticks themselves; the rail never blocks clicks on the messages.

How it works

DSH's web GUI is a Cordis composition. This package is a client plugin that registers a single entry into the conversation.input.dock slot (the additive band above the composer card). It reads the live ConversationSnapshot through the slot's useSession hook, maps each durable kind: 'user' node to a tick, and measures the scrollport ([data-conversation-scroll], [data-composer-seat]) to lay the rail out on the left edge. On mount it uses the scoped conversation service's loadOlder() action to fetch earlier pages automatically until the session history is complete; each returned page adds ticks immediately. It defines no new service.

Positioning is computed against the same stable data attributes the product itself uses ([data-conversation-scroll], [data-chat-flow], [data-chat-anchor-key], [data-composer-seat]). The rail is constrained to the visible conversation area, and its empty gutter is pointer-transparent so it does not block conversation or Session Log scrolling. Long histories use an independent rail scrollport; scrolling the rail does not scroll the conversation.

Install

Requires a DeepSeek Harness deployment with the browser client — that is the desktop app (Web UI embedded) or the web version alike. The rail is pure presentation; it renders only where the conversation composer exists.

pnpm add @lcthe/dsh-timeline-rail

Then add the plugin row to your cordis.yml at the same include level as the bundle rows:

- insert:
    - id: dsh-timeline-rail
      name: '@lcthe/dsh-timeline-rail'

Full wiring details live in INSTALL.cordis.yml.md.

Alternative: load in-session as a dynamic plugin

DSH web also ships a first-class dynamic-Cordis tool. If you are in a session and just want to try it, ask the agent to load the plugin (it can cordis_define + cordis_run this package). This is the recommendable route for quick evaluation; the npm package is the stable, shareable form.

Peer dependencies

Development

pnpm install
pnpm run build     # typecheck (tsc) + bundle (tsdown) -> lib/

• lib/index.js, lib/invariant.js — node-half ESM for the Host Loader.
• lib/client.js — the browser bundle in DSH's __ModuleLoader__.load({ id, factory }) closure format, with CSS modules inlined and auto-injecting a <style data-plugin>.
• lib/types/** — emitted TypeScript declarations.

Known limitations and deferred work

• The rail renders only in the web client; headless/TUI profiles have no composer slot, so nothing shows there.
• Ticks are evenly spaced (one per user message) at a fixed 12px gap. Long histories make the rail content independently scrollable rather than compressing the gap; the ticks still do not represent each message's true scroll position. A real-position "minimap" mode is a natural follow-up.
• Message previews clamp the user message to 2 lines and the assistant reply to 3 lines; longer text is truncated without an affordance to expand in the rail itself (clicking the tick already jumps you to the full message).
• The plugin targets the slot contract as of the 0.0.1-rc.1 release line of the Harness client packages. If the conversation.input.dock contract changes in a later RC, this package may need a bump.

License

MIT