dsh-mcp-apps

Using MCP Apps (interactive HTML tool panels) inside DeepSeek Harness has traditionally forced protocol hosting and presentation to be bundled together, making it hard to reuse an existing MCP connection and leaving untrusted App code in the same origin as the host document. dsh-mcp-apps splits these concerns into two independent plugin rows: a Host row that shares the live MCP SDK connection, its authentication, and reconnect lifecycle, and a Web row that loads App HTML inside a double-iframe sandbox. The two are decoupled and can be installed independently or combined as needed.

The renderer supports three display surfaces: inline, a right-side fullscreen panel, and picture-in-picture. A single AppBridge session moves between them without remounting the iframe, so internal App state such as counters and form values persists across mode switches. On the security front, untrusted App code runs in an opaque-origin document with CSP installed before any App code executes, every relay message is validated against expected parent and child windows and origins, external navigation is restricted to HTTP(S) in a new tab, and inline height is clamped to the 96-720 px range.

This plugin is well suited for DSH Web-profile users who need MCP Apps without pulling in the full Agent Plugins Bridge, and for compositions that already ship the official Host and only need a minimal renderer. TUI and terminal clients can install the Host package on its own and supply their own text-fallback or open-in-browser renderer, avoiding execution of arbitrary App HTML in a terminal.