DeepSeek Harness

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DeepSeek Harness (dsh) is an open-source agent harness developed by DeepSeek AI.

It is built on an everything-is-a-plugin architecture and powered by Cordis, whose design is described in A Programming Paradigm for Spatiotemporal Composability.

Documentation: https://deepseek-harness.github.io/deepseek-harness/

Developer preview

DeepSeek Harness is in developer preview and iterating rapidly. THERE WILL BE COMPATIBILITY-BREAKING CHANGES.

Review the safety notice before running the project.

Run

Run from npm

Install Node.js, then run:

npx @deepseek-ai/dsh web

The command starts the Web UI at http://127.0.0.1:3080 by default and opens it in the default browser for a local launch. An SSH launch only prints the host URL because the SSH client or editor owns the local forwarded address. Pass --no-open to run the server without opening a browser. See Web UI guide.

Run from source

To run from a repository checkout:

git clone https://github.com/deepseek-ai/deepseek-harness.git
cd deepseek-harness
pnpm install
pnpm run build
pnpm dsh web

pnpm run build prepares the repository artifacts. pnpm dsh web uses those built artifacts without rebuilding.

Community and support

• Submit feedback or bug reports through GitHub Discussions.
• Add the dsh-plugin topic to your plugin repository for discoverability.
• Join DeepSeek Harness Discord community.

Session Doctor community plugin

The community Session Doctor integration helps operators explain why an agent Session stopped, looped, retried, or produced an incomplete JSONL log.

• Deterministic diagnosis replays persisted Session events and identifies repeated failed tool calls, unchanged failure cycles, tool-error bursts, provider retry storms, token-ceiling turns, sustained context growth, and interrupted turns.
• The Web UI displays findings and can request structured LLM RCA from bounded, payload-free summaries.
• Cross-Session clustering groups recurring detector, category, and recommendation identities so repeated incidents are easier to prioritize.
• Explicit physical repair recovers only a final torn JSONL tail while preserving the valid logical event prefix.

Diagnosis and clustering are read-only. RCA excludes raw messages, tool arguments, call ids, and opaque metadata; physical repair requires an explicit --repair action.

See the Session Doctor bundle for usage and the community repository for the published source snapshot.

Contributing

See CONTRIBUTING.md.

Development

Start with the development guide and architecture documentation.

For agents, follow AGENTS.md.

License

MIT

Third-party dependencies and their licenses are disclosed in THIRD_PARTY_NOTICES.md.