What is DeepSeek Harness?
DeepSeek Harness is an open-source agent app from DeepSeek that runs as a desktop app or a web UI and uses DeepSeek models to organize files, analyze spreadsheets, write documents and slides, and write and fix code. It is built so that tools, skills and even the interface are plugins. It is in public preview worldwide.
What can you do with it?
DeepSeek describes Harness as an open-source harness built on an "everything is a plugin" architecture. In a session you can organize documents, analyze spreadsheets, draft documents and slides, research with cited sources, and work on code: explore a repository, fix bugs, build features and run tests, then review the diff. Results such as Word, Excel and HTML files can be previewed and refined in the conversation.
You can start tasks at any time or schedule recurring work, for example a weekly project summary every Friday, and inspect tool calls when needed. Plugins extend tools, skills and the interface, and a Creator mode lets you build new plugins by describing them in chat. DeepSeek's own super-agent research prototype is packaged as a Harness bundle.
Try it on a small task
Suggested workflow: install the desktop app, open a workspace folder with a small spreadsheet, and ask for a summary with one chart and a short written report. Check that the figures in the report match the sheet and that the agent only wrote files where you expected.
Then point it at a small repository and ask it to fix one failing test. Review the diff before accepting, and look at the tool-call details to see which commands it ran.
Pricing and access
DeepSeek says Harness is in public preview worldwide and open source, with a desktop download and a web UI you can launch from code. The desktop app is available for macOS (Apple silicon) and Windows (64-bit). The interface shown on DeepSeek's page uses DeepSeek-V4.1-Flash as the model, and the plugin list marks Scheduled tasks, Agent teams and Voice input as Experimental.
The Harness page does not list a price for model usage. Expect model calls to follow DeepSeek's own API pricing and check it before running long or scheduled tasks. Because it is a preview, features and behaviour may change.
What stands out
- Everything is a plugin: tools, skills and interface
- Creator mode to build plugins through chat
- Scheduled and background tasks with tool-call details
- Desktop app or web UI launched from code
Before you choose
- Public preview, so features may change.
- Model usage costs are not stated on the Harness page.
- Plugins and scheduled tasks can act on your files; review permissions and outputs.
Go to the source
Sources & further reading
Based on the official documentation below. Features and access can change; check the provider before making a decision.
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