Description
## Symptom
After a Moonlight (HydraExperienceNet stream) process terminates on a Mac Mini kiosk head (cheeky-cactus-86, node-8acd8c19), the hydracluster exec channel to that node becomes unresponsive. The node continues to show as 'online' in the cluster (heartbeats still flowing) but any hydracluster exec command times out.
## Reproduction
1. Start a stream session from cheeky-cactus
2. Terminate the session (delete relay session or kill Moonlight)
3. Attempt hydracluster exec node-8acd8c19 'echo ok' — times out after 60s
## Impact
Cannot remotely inspect or operate the kiosk head until it is physically power-cycled. Discovered during portrait streaming verification on 2026-05-14