Update: Based on further discoveries, the issue here seems that coderd web terminal sessions have gone defunct after the above error. As for what caused it? That's unknown at this time.

If I type cat /dev/zero in the web terminal, I observe 3 issues.

1. I see no output (Actually, this is normal for cat /dev/zero)
2. Opening a new web terminal simply freezes
3. Shortly thereafter, terminal session is closed via: WebSocket failed: socket errored
4. Web terminal to workspace seems permanently defunct, even after waiting a long time and ensuring processes inside the agent are terminated

This also has a pretty significant impact on coderd CPU usage (#11039):

Refs #8556