Where does the bug appear (feature/product)?
Cursor IDE
Describe the Bug
In Cursor 3.11.19, MCP Apps interactive UI views are not displayed when calling tools that declare a UI resource. The MCP tool executes successfully and the agent returns a text response, but the embedded interactive GUI (iframe/view) never appears in the chat.
In Cursor 3.10.11, the same MCP server, configuration, and prompt correctly render the interactive MCP App UI alongside the tool result.
Steps to Reproduce
- Clone reference example: git clone GitHub - modelcontextprotocol/ext-apps: Official repo for spec & SDK of MCP Apps protocol - standard for UIs embedded AI chatbots, served by MCP servers · GitHub ~/repos/ext-apps
- In ~/.cursor/mcp.json add uv run ~/repos/ext-apps/examples/qr-server/server.py --stdio
- In a new Agent chat, send: "Generate a QR code for the page https://example.com "
Expected Behavior
MCP Apps interactive UI should render in Cursor 3.11.x the same way it does in 3.10.11: when a tool declares a UI resource, the host should fetch and display the sandboxed interactive view in the chat alongside the tool result.
Screenshots / Screen Recordings
Operating System
Linux
Version Information
Version: 3.11.19
VS Code Extension API: 1.125.0
Commit: bf249e6efb5b097f23d7e21d7283429f0760b740
Date: 2026-07-12T21:39:24.175Z
Layout: IDE
Build Type: Stable
Release Track: Default
Electron: 40.10.3
Chromium: 144.0.7559.236
Node.js: 24.15.0
V8: 14.4.258.32-electron.0
xterm.js: 6.1.0-beta.256
OS: Linux x64 6.17.0-35-generic
Does this stop you from using Cursor
No - Cursor works, but with this issue