What is DeepSeek Harness? Agent = Model + Harness
What DeepSeek Harness is: an open-source agent harness on Cordis. Not a benchmark, not Claude Code. Everything is a plugin.
Last updated: 2026-08-14
DeepSeek Harness is DeepSeek’s open-source agent harness, released as developer preview on 13 August 2026. License: MIT. Repo: deepseek-ai/deepseek-harness.
Their formula, on the official page:
Agent = Model + Harness
The model is the soul. The harness is what lets an agent see the environment, use tools, and keep working. DSH is that layer: contract, context, execution, evidence, repair — implemented so everything is a plugin.
What it is not
- Not a leaderboard.
- Not a hosted Claude.ai clone. You run
npx @deepseek-ai/dsh weblocally. - Not “the best coding agent on day one.” Early testers said the preset trails Claude Code / Codex. The bet is the kernel.
Cordis
Under the hood is Cordis: mount, unmount, dependencies. Design note: A Programming Paradigm for Spatiotemporal Composability. That is why plugins can be added and removed at runtime without leaving garbage — in theory. In practice, Creator-mode plugins are still in-memory.