dsh-harness-mcp-server

Expose DeepSeek Harness agent capabilities as an MCP server, letting any MCP client (e.g. Hermes) drive Harness to execute real coding tasks.

Hermes is the brain (pro), Harness is the arms (flash) — 1+1>2.

Why this exists

Harness ships a powerful agent runtime (tools, LLM, agents, sessions), but it is a Cordis app, not something another agent can call. This plugin turns Harness inside-out: it starts a real MCP server (StreamableHTTP) inside Harness and bridges Harness's core services — ctx.agents, ctx.agentPresets, ctx.tools — so an external "brain" can delegate real work to Harness's "arms".

Hermes (MCP client, brain)
   │  agent_run / task_inbox (HTTP)
   ▼
dsh-harness-mcp-server (MCP server, :8090)
   │  ctx.agents.create → mount 'standard' preset
   ▼
Harness agent (flash) — full toolset: bash, fs, todo, web…

Tools

| Tool | Direction | Purpose | |------|-----------|---------| | echo | — | Verify MCP connectivity | | harness_list_tools | — | List Harness's registered tool names | | agent_run | Hermes → Harness | Run a task synchronously and return a structured result | | task_inbox | Hermes → Harness | Push a structured task (task + memory context + cwd) to an async queue | | task_result | Hermes ← Harness | Poll a queued task's structured result |

Every task result is structured:

{
  "sessionId": "...",
  "assistantText": "final answer",
  "toolCalls": [{ "name": "bash", "args": "..." }],
  "toolResults": ["command output"],
  "changes": "what was changed",
  "verification": "how it was verified",
  "leftovers": "open issues"
}

This closes the loop between the client's persistent memory and Harness's coding: memory is fed into each task as context, and the result (changes / verification / leftovers) can be persisted back to the client's memory for the next run.

Install

Option A — from npm (recommended)

npm install @chushixixin/dsh-harness-mcp-server

Then reference the plugin from your Harness workspace (see the cordis patch below).

Option B — from source

Clone this repo inside your Harness workspace under packages/mcp/harness-mcp-server/ (the pnpm workspace matches packages/*/*, two levels deep):

cd /path/to/deepseek-harness
mkdir -p packages/mcp/harness-mcp-server
# copy this repo's files there, then:
corepack pnpm install

Register it in tsconfig.host.json references and tsconfig.base.json paths (see the Harness plugin docs), then build:

corepack pnpm exec tsc -b packages/mcp/harness-mcp-server
corepack pnpm run build:lib:host

Run

export DEEPSEEK_API_KEY=...
corepack pnpm dsh web --patch ./packages/mcp/harness-mcp-server/cordis.yml

The MCP server listens on 127.0.0.1:8090 (StreamableHTTP). Point any MCP client at http://127.0.0.1:8090/mcp.

⚠️ Security: by default the server binds to 127.0.0.1 only. It exposes unauthenticated remote code execution — do not bind it to 0.0.0.0 or expose it to the internet/LAN without adding authentication, TLS, and a reverse proxy first.

Hermes client config

printf 'n\nY\n' | hermes mcp add harness_plugin --url http://127.0.0.1:8090/mcp

cordis.yml (patch format)

- insert:
    - id: harness-mcp-server
      name: '@chushixixin/dsh-harness-mcp-server'
      config:
        http: true
        port: 8090
        host: 127.0.0.1        # 默认仅本机; 暴露前必须加认证
        # authToken: 'your-secret-token'     # 可选: Bearer token 认证
        # workspaceRoots: ['/workspace']      # 可选: cwd 白名单

Positioning

This is best used as a fallback tool, not a daily driver: for everyday code edits, drive your primary agent directly. Reach for this when you need context isolation (huge refactors that would blow the client's context) or parallel execution of unrelated tasks.

• The agent session is reused per cwd (avoids re-loading project context on every call — roughly 15–20× cheaper than one-shot dsh headless).
• Bash runs sandboxed (workspace-write): install bubblewrap on the host, or the sandbox will refuse write commands.
• Each new MCP session gets its own McpServer + transport (an MCP McpServer connects to a single transport).

License

MIT