Before starting a stream (e.g. via test or via kiosk assignment), there is no single API call to check whether the target body already has another head streaming to it, or whether a head has a stale assignment pointing to a body that is now serving a different head. This makes it easy to create silent conflicts: two heads assigned to the same body at the same time.
Discovered during mic relay validation 2026-05-17: turbo-pancake-76 (bxl1/cloud-seven, self-service) had a stale stream_url pointing to cosmic-pretzel-98 (10.10.100.12) while cheeky-cactus-86 (bxl1-test) was actively streaming to the same body.
Additionally, PUT /api/v1/heads/{id} with {"stream":{}} does not clear stream_url / stream_url_lan fields (only stream_app_id is cleared), leaving a partial stale assignment that can confuse monitoring.
GET /api/v1/streaming-monitor — returns all heads with a non-empty stream_url grouped by body IP. Flags any body IP that has more than one head assigned. Fields: body_ip, heads: [{id, name, district, venue, app, status}], conflict: bool.
Fix PUT /api/v1/heads/{id} with stream: {} to also clear stream_url and stream_url_lan (not just stream_app_id).
Before assigning a head to a body in tests or scripts, call GET /api/v1/streaming-monitor to confirm the target body is free. Also useful as a pre-flight check before major events.