The `mcp_app_demo` tool and `mcp_app_demo_widget` UI resource presets already
existed in the preset registry, but no config wired them into a server — so
there was no runnable way to reach a rendered MCP App, and therefore no way to
exercise the sandbox proxy path that #1859 broke.
`mcp-app-http.json` composes the two over plain streamable-HTTP. With it, the
Apps tab renders a real widget and the packaging bug is reproducible on demand:
without clients/web/static in the tarball the widget area shows "Sandbox not
loaded: ENOENT … /clients/web/static/sandbox_proxy.html" instead.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XAR2Nr9kXbrywFNUVoTe9F
