After auto-update from 3.9.16 → 3.10.20, MCP Apps no longer render — the tool result shows only text, no iframe. Same servers rendered correctly in 3.9.16. Reproduces across local stdio and remote HTTP servers, and with both the low-level MCP Server and high-level McpServer. Confirmed the same servers still render in Codex, so it’s client-side.
Minimal repro (stdio, MCP SDK only): a tool with _meta: { ui: { resourceUri: “ui://x” } } + a resource at that URI served with mimeType text/html;profile=mcp-app. In 3.10.20 the widget never renders; in 3.9.16 it does. Full ~40-line server available.
Hey, thanks for the report. Yeah, in 3.9.16 the widgets were rendering, and that actually explains it. If it worked back then, MCP Apps rendering must’ve been enabled for your account, and after updating to 3.10.20 that enablement got dropped.
This isn’t a broken pipeline or a server-specific issue. The render code didn’t change between 3.9.16 and 3.10.20, the symptom is the same on both stdio and HTTP across different server types, and it works in Codex since it isn’t gated there. Everything points to the widgets simply not being enabled for your account right now.
The feature is relatively new, it showed up in Cursor 2.6, and it’s rolling out gradually, so access can change depending on version or cohort. That doesn’t mean the feature was removed or that you configured something wrong. Unfortunately you can’t toggle this from your side.
I’ll check with the team to see if we can re-enable it for your account.
Following up after digging into this further - it’s a known issue on our side, and it’s the same one we’re now tracking internally. The interactive MCP App widgets aren’t mounting for setups like yours right now: the tool itself still runs (that’s why you get the text result), but the inline widget doesn’t render. This isn’t your server or config, and it isn’t something you can toggle on your end.
Two things that’d help us pin it down:
Does the widget fail on every tool call, or does it occasionally render?
Does a window reload (Cmd+Shift+P → “Developer: Reload Window”), or toggling the MCP server off and back on in Settings, ever make it appear? If it does, that’s also a temporary workaround.
Thanks, this confirms it. “Fails on every call” and “reload doesn’t help” line up exactly with the known issue we’re already tracking on our side, so it’s not your servers or config, and there’s nothing to toggle or work around right now. We’ve reproduced it internally, and I’ll update this thread once the fix lands.
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.
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.
