Open-source agent harness (developer preview)
DeepSeek Harness
DeepSeek Harness (dsh) is DeepSeek's MIT-licensed agent harness, released as a developer preview in August 2026. It is built on the Cordis plugin system: models, tools, skills, sessions, sandboxes, storage, scheduling, the UI, and the agent loop itself are all swappable plugins. It runs as a local web UI rather than a terminal UI, records everything the model sees in an append-only session log, and can use other providers, local models, or even Claude Code and Codex as plugged-in subagents.
Best for
- Developers building or experimenting with their own agent harness
- Running DeepSeek models in an agent workflow at low cost
- Orchestrating other agents, such as Claude Code or Codex, from one session
Not best for
- Production use: it is a developer preview with breaking changes promised
- Developers who want a terminal-first tool
- Anyone who wants a finished product rather than a framework
Quick facts
- Vendor
- DeepSeek
- Category
- Open-source agent harness (developer preview)
- Platforms
- Web UI, Node.js
- Integrations
- DeepSeek API, Local models, Claude Code, Codex, Cordis
- Pricing
- Free and open source under the MIT license. You pay for the models you connect; DeepSeek API rates apply when you use DeepSeek models.
In Depth: DeepSeek Harness
Key features
- Everything is a plugin, including the agent loop
- Local web UI
- Append-only session log for inspecting, resuming, forking, and replaying
- Standard, Code, Minimal, and custom runtime presets
- Pluggable sandboxes and subagent scheduling
- Other model providers and local models by configuration
Pricing and access
Free and open source under the MIT license. You pay for the models you connect; DeepSeek API rates apply when you use DeepSeek models.
Plans and limits change often. Confirm current pricing on deepseek.com/harness/en/ before you commit.
