DSH MCP Server

A DeepSeek Harness (DSH) plugin that publishes a Model Context Protocol (MCP) server from the running Harness host, so other agent harnesses — Claude Code, Cursor, Codex, another DSH, any MCP client — can call DSH: start sessions, drive turns, read transcripts, and cancel work.

The plugin is a Host-only bundle with zero dependencies (no DSH import, no third-party module), so it installs into a profile and survives Harness upgrades that keep the service contracts.

other harness ──MCP (Streamable HTTP or stdio)──> DSH MCP Server ──> DSH services
                                                                     sessionController / sessionQuery / tools

What it exposes

MCP tool	Purpose
dsh_run_prompt	Start a new DSH session and run one prompt; returns the assistant's final text and the new sessionId. Supports cwd, agentPreset, permissionPreset, model (provider/model), wait: false, timeoutMs.
dsh_continue_session	Send a prompt to an existing session (resuming it if it is cold). Keeps the session's context and workspace; permissionPreset re-pins the session's sandbox mode and approval policy before the prompt.
dsh_list_commands	The slash commands a session's agent can currently run: the global command layer plus whatever that agent's preset composes, so availability differs per agent preset.
dsh_run_command	Run one slash command in a session and return its settled { kind, text, commandId }. line takes a complete command line ("/compact", "/permission danger-full-access"); command (+ optional args) takes a bare name. The command executes immediately without a model turn.
dsh_list_sessions	Visible sessions with title, cwd, running state, archival state, and last activity. Archived sessions are hidden unless includeArchived: true, mirroring the Web UI.
dsh_read_session	Ordered { role, text, seq } transcript of one session (user-authored and assistant messages only), plus the last durable permissionPreset when the session has one. Works while the session is archived.
dsh_cancel_session	Cancel the active turn of a session without dropping its pending inbox.
dsh_archive_session	Archive one session durably: hidden from every grouping surface, and it cannot run a model step until restored. A session with running work is refused unless stopActivity: true (which archives first, then stops that work). Archiving drops the pin.
dsh_unarchive_session	Drop a session from the archive set; it is listed again and returns to its recorded workspace position.
dsh_list_permission_presets	The deployment's permission presets (each bundles a sandbox mode with an approval policy) plus the default for new sessions, for the permissionPreset argument above.
dsh_list_tools	The tools DSH exposes to its own agents, for choosing what a delegated prompt can do.
dsh_status	Endpoint, profile, version, session/live-agent counts, default model, active turns, and the default permission preset.

Archival needs the Host's workspaceRegistry service (@deepseek-ai/dsh-workspace). Without it the two archive tools report that the service is unavailable and listings simply omit the archived field instead of guessing.

Permission presets need the Host's permissionPresets service (@deepseek-ai/dsh-permission-presets). permissionPreset is applied through that service's own set() — the same write path as the GUI /permission command — once the session is live and before its prompt is admitted, so the turn's own tool calls already see the chosen sandbox mode and approval policy. The outcome echoes the applied preset; dsh_read_session folds the session's last durable permission/preset event back into its payload, and dsh_status carries defaultPermissionPreset plus the catalog. Without the service the permission fields are omitted and dsh_list_permission_presets reports that the service is unavailable. A session created without a permissionPreset keeps the deployment default, exactly as a GUI-created session does.

Commands need the Host's commands service and are addressed by agent, not by session: the registry merges a global layer with the layers of the preset that agent is mounted under, so dsh_list_commands must be asked per session and a command such as /compact exists only when that session's preset composes it (standard/ptc/cordis do; minimal does not). Execution goes through the same commands.execute() the Web composer uses: the handler runs immediately, the lifecycle is logged as command/run + command/done, and no model turn is started. kind is success or error; a line the Host would not parse as a command, or a name it does not know, is rejected with the available commands listed.

Resources: dsh://status, dsh://sessions, and the template dsh://session/{sessionId}.

Endpoint and authentication

On activation the plugin registers POST /mcp on the Harness web server (default http://127.0.0.1:19387) and writes connection details to:

$DSH_HOME/mcp/dsh-mcp-endpoint.json      # mode 0600
{ "url": "...", "token": "...", "stdioBridge": "...", "tools": [...] }

Every request must present the bearer token:

Authorization: Bearer <token>

The token is generated per activation unless you configure a fixed one. Set a fixed token whenever another harness keeps a saved config, because a generated token changes on every Harness restart. In the desktop profile the dsh-mcp-server row carries one:

- id: dsh-mcp-server
  disabled: false
  config:
    token: "<fixed token>"     # mirrored in the endpoint file and in the selfcheck bundle

Requests that already pass DSH's own connection trust (ctx.connection) are also accepted, so local tooling that holds the Harness token works too.

The endpoint file is owned by the activation that wrote it: on a config hot-reload the outgoing instance removes it only when it is still the owner, so the replacement instance's file is never deleted mid-reload.

Configuration

The bundle row in cordis.patch.yml accepts (all optional):

Field	Default	Meaning
path	/mcp	Route path on the Harness web server.
token	generated	Fixed bearer token; set this so external configs stay stable across restarts.
url	$DSH_WEB_URL or http://127.0.0.1:19387	Advertised base URL written to the endpoint file.
endpointFile	$DSH_HOME/mcp/dsh-mcp-endpoint.json	Where connection details are published.
writeEndpointFile	true	Publish the endpoint file at all.
allowConnectionAuth	true	Also accept requests admitted by ctx.connection.
defaultCwd	Harness default	Working directory for sessions started without cwd.
defaultModel	Harness default model	{ provider, model, reasoningEffort? } for sessions without an explicit override.
turnTimeoutMs	1800000	Default wait ceiling for a tool call that waits for a turn.
maxConcurrentTurns	8	Concurrent waited turns before new calls queue.
maxBodyBytes	8388608	Request body ceiling.
instructions	built-in text	Replaces the instructions handed to the calling model.

Example row:

- insert:
    - id: dsh-mcp-server
      name: '@local/dsh-mcp-server'
      config:
        token: !!js process.env.DSH_MCP_TOKEN
        defaultCwd: /Users/me/work

Connecting another harness

1. Streamable HTTP (no extra process)

Point the client at the endpoint with the bearer token:

// Claude Code / Cursor style MCP config
{
  "mcpServers": {
    "dsh": {
      "type": "http",
      "url": "http://127.0.0.1:19387/mcp",
      "headers": { "Authorization": "Bearer <token from dsh-mcp-endpoint.json>" }
    }
  }
}

2. stdio (harnesses that only spawn a command)

bin/dsh-mcp-stdio.mjs is a dependency-free stdio↔HTTP bridge. It discovers the endpoint from $DSH_HOME/mcp/dsh-mcp-endpoint.json (override with --url/--token or DSH_MCP_URL/DSH_MCP_TOKEN):

{
  "mcpServers": {
    "dsh": {
      "command": "node",
      "args": ["<path-to-dsh-mcp-server>/bin/dsh-mcp-stdio.mjs"]
    }
  }
}

It forwards JSON-RPC messages verbatim, cancels the upstream request when the client sends notifications/cancelled, and keeps stdout clean (diagnostics go to stderr).

Because GUI clients launch with a minimal PATH, point command at an absolute Node binary and rely on the bridge's ~/.dsh discovery (both verified with only HOME and PATH set):

Client	Config file	Entry
Claude Code (user scope)	~/.claude.json	mcpServers.dsh
Claude Desktop	~/Library/Application Support/Claude/claude_desktop_config.json	mcpServers.dsh
ChatGPT desktop / Codex	~/.codex/config.toml	[mcp_servers.dsh]

# Codex / ChatGPT desktop
[mcp_servers.dsh]
type = "stdio"
command = "/absolute/path/to/node"
args = ["<path-to-dsh-mcp-server>/bin/dsh-mcp-stdio.mjs"]
startup_timeout_sec = 60

Restart the client after editing its config. A cloud MCP client (for example a web connector) cannot reach a loopback endpoint at all — that needs a tunnel and a deliberate networking change.

3. DSH as its own MCP client

DSH ships @deepseek-ai/dsh-mcp-client; a row like this registers this server's tools inside DSH as mcp__dsh__dsh_run_prompt, …:

- insert:
    - id: mcp-dsh
      name: '@deepseek-ai/dsh-mcp-client'
      config:
        serverName: dsh
        transport: streamable-http
        url: http://127.0.0.1:19387/mcp
        headers:
          Authorization: !!js '`Bearer ${process.env.DSH_MCP_TOKEN}`'

Install into a profile

git clone https://github.com/baitouwuya/dsh-mcp-server.git
# then, from the Harness UI / plugin_manager:
plugin_manager install_bundle --target /path/to/dsh-mcp-server

or, equivalently, action: install_bundle with the absolute package directory as target.

Self-check bundle (optional)

selfcheck/ is a second, tiny bundle (@local/dsh-mcp-selfcheck) that registers DSH's own MCP client against this server, so the published endpoint is continuously exercised and its tools appear inside DSH as mcp__dsh__*. It is pure verification — disable or skip it if you do not want a self-loop in every session:

plugin_manager install_bundle --target /path/to/dsh-mcp-server/selfcheck

The committed cordis.patch.yml carries no literal token (this is a public repository): set DSH_MCP_TOKEN in the Harness environment, or patch the mcp-dsh-selfcheck row from your own private profile, with the token the server is configured with.

Verification

node test/mcp-self-test.mjs            # 11 transport checks, no Harness needed
node test/plugin-integration-test.mjs  # 28 checks: apply(), endpoint file, tools, transcript filter,
                                       # archival tools, permission presets, commands, hot-reload ownership
node test/stdio-bridge-test.mjs        # 4 checks, needs a RUNNING Harness (one real delegated turn)
node test/live-e2e-test.mjs            # 34 checks over HTTP: protocol, resources, all twelve tools,
                                       # archive/unarchive, permission presets, commands, error paths,
                                       # 4 real turns (needs a Harness)

Live checks used during development also covered: a real MCP client exchange against the running Harness, an end-to-end dsh_run_prompt → dsh_continue_session → dsh_read_session flow, permission presets applied and re-pinned over MCP and folded back out of the transcript, a command executed without adding a model message, detached start + cancel, and the stdio bridge.

Notes and limitations

• Code changes need a Harness restart. Re-enabling a bundle reloads its row but reuses the already-imported module generation, so edited plugin code only takes effect after restarting DSH. Config changes reach the running instance immediately; changing a bundle's package path may report restart-required.
• The bearer token is a local secret. The desktop profile keeps it in $DSH_HOME/profiles/desktop/cordis.patch.yml, and selfcheck/cordis.patch.yml repeats it. Rotate by updating both places. It authorizes full DSH session control over loopback, so treat it accordingly.
• Localhost only. The endpoint rides the Harness web server, which binds loopback. Exposing it to another machine is a deliberate networking change, not a plugin setting.
• Approval and user questions. A turn started over MCP runs with the session's own approval and sandbox policy (permissionPreset, or the deployment default); if a delegated turn needs approval, the prompt appears in the Harness GUI like any other session. Switching a session's preset from the GUI (/permission) and over MCP write the same durable events, so the last writer wins per session.
• Commands are immediate and per agent. dsh_run_command runs on the addressed agent's command layer (global + that agent's preset), so a preset-scoped command such as /compact may be absent for another session. It is not queued behind a running turn and it can mutate session state (/permission), so it carries the same authority as typing the command in the GUI; dsh_list_commands first is the way to know what a session accepts.
• Sessions started over MCP are ordinary DSH sessions: they appear in the Harness session list and can be opened and continued in the GUI.

License

MIT