DeepSeek Harness
FreeDeepSeek's open-source agent runtime, where everything is a plugin
An agent runtime DeepSeek open-sourced on 13 August 2026 under the MIT licence. Models, tools, skills, sessions, sandboxes, filesystems, orchestration loops and even the UI are all implemented as swappable, extensible plugins. One npx command brings up a local web UI where the agent reads and edits files in a workspace you choose and runs commands.
Why we picked it
Released on 13 August 2026, past 66,000 stars within a day and now at 215,900, MIT-licensed, with more than fifteen thousand commits in the repository.
Architecturally it bets on one idea: everything is a plugin. Models, tools, skills, sessions, sandboxes, filesystems, loops, orchestration and the UI are each a replaceable plugin on top of the Cordis meta-framework. That is the opposite of most agent products, which weld the model and the interface together — swapping the reasoning loop, attaching your own sandbox or taking the core without the UI is a plugin change rather than a fork.
Getting started is npx @deepseek-ai/dsh web, which serves a local web UI at http://127.0.0.1:3080
by default. From source it is clone, then pnpm install && pnpm run build && pnpm dsh web. A
headless mode exists for pipelines.
It is model-agnostic and not tied to DeepSeek's own models.
To be clear about:
- This is a developer preview and the project says compatibility-breaking changes are expected. It moves fast, and a plugin written today may need edits next version. Weigh that before making it a long-term dependency.
- The interface is a browser-based web UI, not a TUI. Terminal purists will likely prefer OpenCode.
- You still bring your own model, and token costs go to the model provider. Local models cost nothing.