The Supervisor proxy answers 502 to every add-on read, write and websocket
until Core is RUNNING (proxy.py api()/websocket() -> check_api_state()), so
the add-on cannot control while a slow integration holds HA's start, even
with its entities live. Measured on a safety112 repro stack with the
2026.08.0 proxy code: first write 1.0-4.4 s after RUNNING, 238-300 s after
live readings. Not routed around (DECISIONS/SAFETY-112-...).
While the API does not answer, the first status row is red and is the
banner ("Waiting for Home Assistant to finish starting"), Home shows a
"waiting" state in EN/NL instead of "Needs you now", and the log adds a
"still waiting" line every 5 minutes and the wait's length at the end.
A safety stop, a stalled loop or shadow mode keeps its own headline.
Control, writes, heartbeat and the stand-down are unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>