DeepSeek Harness Creator Mode builds agent plugins from a prompt

DeepSeek Harness Creator Mode lets the agent write its own plugins. On November 2 the DeepSeek Harness team announced the feature: describe a tool in plain language, and Harness writes the plugin, installs it and keeps it for later sessions. TechNode covered the demos on November 3. For a small team, this is the cheapest path yet to a custom internal tool. It is also an agent generating and running unreviewed code on your machine, which is the exact thing we told you to watch for.

What actually happened

• The pitch. Creator Mode turns a request into a working plugin inside Harness. The launch demos included a design workspace, a sandbox game, a 3D visualizer for language models and a video editing workbench.
• Seven prompts. DeepSeek published seven demo prompts in Chinese and English, including a paper reader, a poster designer and a dashboard that tracks conversation statistics. You paste one into Harness, select Creator Mode, and watch.
• The caveat DeepSeek itself gave. Some demo plugins were refined over several rounds of conversation, so one prompt may not reproduce the video.
• What Harness is. The GitHub repo describes dsh as an open-source agent harness where "everything is a plugin," built on the Cordis framework and released under the MIT license. It is a developer preview and the README warns, in capitals, that breaking changes are coming. It runs with npx @deepseek-ai/dsh web and serves a local UI on port 3080. As of today it shows about 271,000 stars.

We covered the Harness runtime when it launched, and we covered the CVE where the agent unlocked itself out of its own sandbox. Creator Mode sits on top of both.

Why it matters for your business

The upside is real. A plugin that pulls your Shopify orders into a morning dashboard, or reads supplier PDFs into a table, is now a paragraph of text instead of a contractor invoice. MIT license means you own what it writes.

The risk is that a generated plugin is code that nobody read. It runs with the same permissions as every other plugin in your Harness, next to the connectors that hold your API keys. The README points you to a safety notice before you run anything. Read it, then add your own rules:

1. Run Harness in a container or a throwaway VM, never on the laptop with your production credentials.
2. Treat every Creator Mode output as a pull request. Read the diff before you enable the plugin. If you cannot read it, do not run it.
3. Give plugins scoped tokens with the smallest permissions that work, and rotate them.
4. Pin the Harness version. A developer preview that promises breaking changes will break your plugins at the worst time.

An agent that extends itself is a productivity tool and an attack surface at the same time. Decide which one you are running.

Sources: DeepSeek Harness announcement on X, TechNode, deepseek-ai/deepseek-harness on GitHub.