Open in VS Code for the web fails ... tunnel 400 error ?

Your Cloud Shell session works, but “Open in VS Code for the Web” fails while creating the Service Bus tunnel. Because the 400 response occurs in several browsers, another PC, and an Azure VM, local cache or VS Code folders are unlikely causes. Microsoft documents this feature as transferring the Cloud Shell session to browser-based VS Code, so unchanged folders fit a failure before the remote editor starts. First, open Cloud Shell Settings and select Reset user settings. This ends the session and unmounts linked storage but does not delete the Azure file share. Reattach the share and retry. Confirm that HTTPS and WebSocket traffic to the Service Bus endpoint is allowed. If it still fails, select View Logs and open an Azure support request with the UTC time, region, tenant and subscription IDs, and correlation or activity IDs. The 400 response does not identify a user-side fix.