In DeepSeek Harness (DSH), after a fork of the same conversational turn, the common question is not “which branches exist,” but “what exactly differs in the public history between two branches.” Opening sessions one by one and scrolling back and forth makes it hard to compare long responses, tool traces, and token costs. dsh-fork-diff presents this information in a filterable two-pane view for side-by-side comparison of related session branches.

Plugin Positioning

This is a read-only, branch-aware conversation diff plugin designed for DeepSeek Harness. It aligns the current session with the public history of a parent, child, or sibling branch, and highlights differences in responses, tool calls, and tool results. The plugin is entirely read-only: it does not create forks, modify files, or write session events.

Core Features

  1. Branch discovery: Automatically discovers parent, child, and sibling branches of the current session without including unrelated sessions.
  2. Content alignment: Aligns user messages, final assistant responses, tool calls, and tool results.
  3. Diff highlighting: Distinguishes unchanged, modified, left-only, and right-only content, and provides line-level text highlighting.
  4. Statistics summary: Summarizes user messages, responses, tool calls, elapsed time, and visible token usage.
  5. Interaction and views: Supports switching comparison targets, switching between “Diffs only” and “All,” and opening the corresponding session from a branch summary. Supports desktop two-pane and mobile single-pane layouts, as well as closing with Escape, focus trapping, and focus restoration.
  6. Pagination and alignment: Provides reverse pagination for the full history, with safeguards for cancellation, duplicate sequence numbers, no progress, non-contiguous pages, and page-count limits. Large histories and long text explicitly enter fast alignment mode, avoiding presenting approximate results as exact results.

Installation and Activation

This plugin requires DeepSeek Harness 0.1.0-rc.5 or a compatible version, and Node.js ^22.19.0 || >=24.0.0.

Install the prebuilt tarball into the web profile:

dsh plugin --profile web add https://github.com/chouyong/dsh-fork-diff/releases/download/v0.1.0/dsh-fork-diff-0.1.0.tgz

After installation, start or restart the corresponding profile:

dsh --profile web

Typical Usage

  1. Open a DSH session that has parent, child, or sibling branches.
  2. Click “Compare branches” in the session title bar.
  3. Select the relevant branch from “Comparison target.”
  4. Switch between “Diffs only” and “All,” or open the corresponding session from a branch summary.

Privacy and Boundaries

The plugin only reads the public session list and the sessions.history API exposed in the DSH browser:
- It does not create forks, write session events, or modify files.
- It does not restore background agents, inject prompts, or upload session content.
- It does not read cookies, credentials, hidden databases, or unpublished runtime state.
- It does not judge which branch is “better” or perform merge or cherry-pick.
- The client summary does not expose a persisted seedLength, so v1 does not claim an exact fork point or an event-level common ancestor.

Ecosystem Context

The philosophy of DeepSeek Harness is “everything is a plugin.” This plugin is hosted on GitHub and is available in the community directory. The directory is a standalone site and has no official affiliation with DeepSeek / High-Flyer.

This tool provides developers with a practical solution for quickly identifying differences in branched conversations, without manually handling complex session histories.

Plugin directory | GitHub repository