dsh-mcp-diff

A client plugin for the DeepSeek Harness (Web GUI) that turns every file mutation it can confidently parse into a uniform diff card in the chat — collapsed by default, with per-line highlighting (green for additions, red for deletions).

Covers the filesystem MCP server (edit_file / write_file / move_file / create_directory), the built-in DSH tools (edit / write), and recognizable file-mutating bash commands — one look for all of them. Bash shapes the parser cannot confidently identify (chmod, ln, rsync, dd, git state changes, …) keep the plain terminal card: a missed card beats a wrong one.

Why

By default DSH draws a diff only for its own file tools (edit, write), with its own renderer. When the agent edits files through the @modelcontextprotocol/server-filesystem MCP server, the call is named mcp__filesystem__edit_file / mcp__filesystem__write_file — there is no registered toolview for it, so the chat shows only a generic block with no diff.

The plugin:

• registers a toolview under the MCP keys and builds the diff from the server response (a ready unified diff with context and @@ headers) or from the call arguments when there is no response yet (write_file, a still-running edit_file);
• also overrides the built-in edit / write, unifying their contextual hunks (a per-line LCS: shared lines read as neutral context instead of being doubled);
• renders move_file and create_directory as compact informational cards — source → destination, the created path, both workspace-relative — since they carry no diff lines;
• makes every card's path openable: a click hands it to the host's file opener (the same channel the native tool rows use), which resolves it against the session workspace and opens the file in your IDE/editor;
• renders everything as one card built on a native <details> — collapsed by default, the header shows the path + +N -M, and it expands on click.

Bash edit cards

When the agent edits files through bash instead of a file tool (a python3 - heredoc with old/new blocks, sed -i, cat > file <<EOF, tee, > file redirects), DSH shows a plain terminal block and tracks no "files touched" — so the plugin owns the bash toolview and adds a card only for commands it can confidently parse as line mutations:

• replace — a heredoc script that reads a file, .replace()s old/new triple-quoted blocks and writes it back: the card shows the file, real del/add lines and +N -M derived from those blocks;
• write — cat > f <<EOF, tee [-a] f <<EOF, bare > f / >> f: the path always, the added lines when the content is spelled out in the command;
• in-place — sed -i / perl -pi with explicit file tokens: the path only;
• path ops — mkdir, mv, cp, rm, touch with literal path arguments: an informational card naming the operation and its paths (no diff lines exist for these). Anything non-literal — $VAR, globs, cd chaining — keeps the plain terminal card.

Every other bash call (ls, git status, builds, grep…) keeps a plain terminal-like card — it is never turned into a diff. Such a card gains a small warning chip when the command matches an unambiguous destructive signature (rm -rf, chmod 777, git reset --hard, git checkout ., git clean -f, curl … | sh, mkfs, dd of=, shred) — an annotation of the command text, never a mutation claim.

The card is marked bash edit and carries a footnote: intended change parsed from the bash command — not an edit/MCP tool result. The client sees only the command text and its output (no filesystem access), so the diff is what the script claims to do, with the full command and the output tail one click away. Dynamic paths ($VAR, globs) and unsupported shapes are left unrendered on purpose: a missed card is better than a wrong one.

Open file links

Every path a card shows — the diff header, a move_file destination, the paths of a bash mutation — is a link: clicking it calls the host's file opener (openFile), the same channel the native tool rows use. The host resolves the path against the session workspace (bash paths against the command's own working directory) and opens the file in your IDE/editor. A path without a workspace context (an unusual host setup) stays plain text, and so does any path that would resolve outside the session workspace — an absolute or ~ target parsed out of a bash command, .. traversal, a bash call working outside the workspace. Rendered content never triggers an open of an arbitrary host file.

Install

# from npm (prebuilt, recommended)
dsh plugin --profile web add dsh-mcp-diff

# or from GitHub (built on install)
dsh plugin --profile web add github:Fakek0f3sT/dsh-mcp-diff

dsh plugin add is a pnpm forwarder: it adds the package to your profile (~/.dsh/profiles/web) and, since the plugin declares dsh.bundle, automatically includes it in dsh.profile.bundles — nothing to wire by hand. Installed from GitHub, lib/ is built in place (the prepare script); from npm it ships prebuilt.

Important: DSH picks up its plugin set only at startup — after installing, restart dsh web and refresh the GUI page.

Check that the bundle is served:

curl -s http://127.0.0.1:3080/plugins/dsh-mcp-diff/client.js | head -c 80

git clone https://github.com/Fakek0f3sT/dsh-mcp-diff.git
cd dsh-mcp-diff && npm install && npm run build
cd ~/.dsh/profiles/web
npm install /path/to/dsh-mcp-diff

{
  "dependencies": { "dsh-mcp-diff": "link:./node_modules/dsh-mcp-diff" },
  "dsh": { "profile": { "bundles": [ "…", "dsh-mcp-diff" ] } }
}

Configuring for another MCP server

The toolview keys are set for the server name filesystem. If your filesystem MCP server is named differently (the serverName field in the config), edit the key constants in src/client/index.tsx (MCP_TOOL_KEYS, MCP_MOVE_FILE_KEY, MCP_CREATE_DIR_KEY — keys of the form mcp__<serverName>__…). The edit / write keys live there too — remove them if you do not want to override the built-in renderer.

Development

npm install
npm run build
npm run test   # the self-checks (bash-mutation, diff, path-containment) via tsx

Compatibility

Tested on DSH 0.1.1-rc.2. The plugin imports only platform modules (react, ui-primitives, ui-slots, runtime/client) — ui-tool internals are not imported.

License

MIT