help with jupyter behind a proxy

I am having trouble running Jupyter behind a proxy. The kernels seem to not connect properly to the websocket.

On the browser console, I see this error:
```
WebSocket connection to 'wss://proxytestme.systems/jupyterproxy/8890/api/kernels/2668b22d-dae5-4b11-b9ef-cca2ffb60e50/channels?session_id=649DE08BF5FB41FE892DB51D1B59AC34' failed: Invalid frame header
Kernel.start_channels @ kernel.js:461
```

On the server side, I see the following in the logs:
```
[W 23:45:02.028 NotebookApp] 404 GET /jupyterproxy/8890/api/kernels/2668b22d-dae5-4b11-b9ef-cca2ffb60e50/channels?session_id=649DE08BF5FB41FE892DB51D1B59AC34 (127.0.0.1) 2.05ms referer=None
[W 23:45:02.044 NotebookApp] 404 GET /jupyterproxy/8890/api/kernels/2668b22d-dae5-4b11-b9ef-cca2ffb60e50/channels?session_id=649DE08BF5FB41FE892DB51D1B59AC34 (127.0.0.1) 1.65ms referer=None
[I 23:45:02.049 NotebookApp] Adapting to protocol v5.0 for kernel 2668b22d-dae5-4b11-b9ef-cca2ffb60e50
```

Right after these logs on the server, I also see a "Client disconnected" message on the proxy.

Start by checking the proxy configuration and comparing the browser WebSocket URL with the NotebookApp 404 logs. The issue names no repository files or tests; done would require identifying the proxy/WebSocket routing cause and documenting or fixing it.

Written by the indexing model from the issue text.