DeepSeek Harness is now in developer preview for agent harness developers worldwide — source code included.
Every capability is a plugin that can be swapped or recomposed: models, tools, skills, sessions, sandboxes, storage, loops, scheduling, and the UI.
A harness lets an agent understand its environment, use tools, and keep working in real-world settings.
The Cordis kernel manages plugin mounting, unmounting, and dependencies. Agent capabilities live in the plugins.
Plugins provide every agent capability, including models, tools, skills, sessions, sandboxes, storage, loops, scheduling, and the UI. Cordis services and events let the plugins work together.
Developers can select, swap, or extend any capability in configuration without changing the DeepSeek Harness source code.
DeepSeek Harness is built onCordis’s plugin system. Plugins provide every agent capability, including models, tools, skills, sessions, sandboxes, storage, loops, scheduling, and the UI. Cordis services and events let the plugins work together. Developers can select, swap, or extend any capability in configuration without changing the DeepSeek Harness source code.
Everything the model sees is recorded in an append-only session log: system prompts, reasoning, tool calls and results, subagent scheduling, and every context injection. In the Trajectory view, you can inspect these records by source. Resume, fork, search, and replay all operate on the same event stream.
DeepSeek Harness is built onCordis’s plugin system. Plugins provide every agent capability, including models, tools, skills, sessions, sandboxes, storage, loops, scheduling, and the UI. Cordis services and events let the plugins work together. Developers can select, swap, or extend any capability in configuration without changing the DeepSeek Harness source code.
Everything the model sees is recorded in an append-only session log: system prompts, reasoning, tool calls and results, subagent scheduling, and every context injection. In the Trajectory view, you can inspect these records by source. Resume, fork, search, and replay all operate on the same event stream.
Install Node.js, then launch the Web UI with npx.
Clone the full source and follow the setup instructions in the repository.