MCP Apps support for DeepSeek Harness

[sugarforever]

I built @sugarforever/dsh-mcp-apps, a community plugin that turns the DeepSeek Harness Web profile into an MCP Apps host.

It connects Harness to MCP servers over stdio or Streamable HTTP. Ordinary MCP tools remain normal Harness tools, while tools that expose an MCP App UI are rendered as sandboxed interactive views directly in the conversation.

Highlights:

• MCP Apps extension negotiation (io.modelcontextprotocol/ui)
• text/html;profile=mcp-app resources
• stdio and Streamable HTTP transports
• model-visible, app-visible, and app-only tools
• structured tool results and app-to-server tool/resource calls
• resource CSP metadata and iframe permission policies
• lifecycle cleanup for tools, connections, RPC routes, slots, and app bridges

Install the published plugin into the Harness Web profile:

npx @deepseek-ai/dsh plugin --profile web add @sugarforever/dsh-mcp-apps

Then start or restart Harness:

npx @deepseek-ai/dsh web

The package currently includes a default public VibeFun MCP Apps configuration, and the bundled profile patch can be edited to connect another MCP server.

Repository, documentation, examples, architecture, and security notes:

https://github.com/sugarforever/dsh-mcp-apps

Feedback, compatibility reports, and contributions are welcome in the plugin repository.