JetBrains Gateway WSL project does not open: "Connecting to remote host" closes in mirrored networking

Problem

A project in WSL opened or created through JetBrains Gateway (WSL connection) does not open. The JetBrains Client dialog Connecting to remote host... shows for about two minutes, then closes without an error message. A new project is not added to the Recent WSL Projects list.

The Gateway idea.log shows a client timeout on each attempt:

INFO - #c.j.g.s.ClientOverSshTunnelConnector - Port forwarding done, local join link=tcp://127.0.0.1:5990#...
INFO - #c.j.g.t.ThinClientHandle - Message from thin client <id>: ProjectOpenFailed(exitCode=178)

The WSL configuration file %UserProfile%\.wslconfig contains:

[wsl2]
networkingMode=Mirrored

Cause

JetBrains Client connects to the IDE backend on 127.0.0.1:5990 on the Windows side. For a WSL connection, Gateway does not forward this port itself and expects WSL to make the backend port available on Windows. With networkingMode=Mirrored, the connection to the backend times out (exit code 178).

Resolution

1. In %UserProfile%\.wslconfig, change networkingMode=Mirrored to networkingMode=NAT.
2. In PowerShell, run wsl --shutdown to apply the change. This command stops all running WSL distributions.
3. In JetBrains Gateway, open or create the project again.