DeepSeek Harness
DeepSeek Harness is an open-source agent harness by DeepSeek AI. Every capability is a plugin that can be swapped or recomposed: models, tools, skills, sessions, sandboxes, storage, loops, scheduling, and the UI.
Everything is a plugin. Every run is traceable.
DeepSeek Harness is built on Cordis. Plugins provide every agent capability, and each run can be inspected through the Trajectory view.
Everything is a plugin
Models, tools, skills, sessions, sandboxes, storage, loops, scheduling, and UI are swappable plugins.
Every run is traceable
System prompts, reasoning, tool calls, subagent scheduling, and context injection are recorded in an append-only Trajectory log.
Multiple runtime modes
Standard, Code, Minimal, and Creator modes cover coding, multi-step orchestration, benchmarking, and custom presets.
Cordis-powered
Cordis services and events let plugins work together without changing DeepSeek Harness source code.
Open source · MIT
DeepSeek Harness is an MIT-licensed open-source project, available in developer preview.
Multi-agent orchestration
Planning, goals, subagents, and workflows are provided as composable agent capabilities.
Built for agent harness developers
Use DeepSeek Harness for coding agents, model-generated orchestration, and custom plugin presets.
Full-featured coding agent
Use Standard mode with file editing, shell, file and web search, skills, planning, goals, subagents, and workflows.
Code-mode orchestration
Use model-generated TypeScript to combine multi-step tool calls in one program through the Code Mode SDK.
Custom agent presets
Inspect the runtime, test Cordis plugins in memory, and combine them into new modes with Creator mode.
Start with DeepSeek Harness in three steps
Sign in on this site, choose a plan, and get ready to use DeepSeek Harness in your browser without installing anything.
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Choose a plan
Pick the monthly or annual subscription that fits your usage.
Use DeepSeek Harness
After your subscription is active, open the hosted Harness experience and start working.
Open-source infrastructure, built to be composable
DeepSeek Harness is an MIT-licensed developer preview powered by the Cordis plugin architecture.
v0.1 Developer preview release, available on npm and from source.
Developer preview release, available on npm and from source.
Everything is a plugin Models, tools, skills, sessions, sandboxes, storage, loops, scheduling, and UI.
Models, tools, skills, sessions, sandboxes, storage, loops, scheduling, and UI.
4 runtime modes Standard, Code, Minimal, and Creator modes for different agent workflows.
Standard, Code, Minimal, and Creator modes for different agent workflows.
Frequently asked questions
The fastest answers to the questions people ask first about DeepSeek Harness.
Start using DeepSeek Harness
Sign in, choose a plan, and get ready to use DeepSeek Harness in your browser without installing anything.