/healthz is hit over 127.0.0.1 (the deploy probe) and localhost (the container's
own healthcheck) before any proxy has supplied a real Host header. With only the
public domain in ALLOWED_HOSTS, Django 400s both, the container is marked unhealthy
forever, and the deploy never goes green — which is how the first real deploy
failed.
The loopback is now appended unconditionally. It widens nothing: gunicorn binds to
the loopback only and the proxy owns the public domains, so nothing external can
present these hosts. Tested with a non-loopback ALLOWED_HOSTS.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Bernard Siebens
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