Cannot inspect network activity: The subprotocol '' is invalid

[martynasbp]

Hello,

Since yesterday I am unable to use network inspection tool on devtunnels.

This affects all ports I have open. No traffic ever shows up on the screen.

If I bring up the browser's dev tools looks like I get the following error:

Uncaught (in promise) SyntaxError: Failed to construct 'WebSocket': The subprotocol '' is invalid.

Seems like there is a bug that prevents websocket connection from being established.

---

devtunnel version
Tunnel CLI version: 1.0.1516+7e996fe917

Tunnel service URI        : https://global.rel.tunnels.api.visualstudio.com/
Tunnel service version    : 1.0.1519.52590 (6ecd531c46; 2025-10-21 22:43:10Z)
Tunnel service cluster    : euw