@supabase/ssr derives the auth cookie storage key from the hostname of the URL
it is given (sb-<sub>-auth-token). After routing server-side clients at the
internal host (kong-prod), the server looked for sb-kong-prod-auth-token while
the browser had set sb-api-auth-token, so server-side getUser() never found the
just-established session and bounced the user off the MFA challenge back to
/login. Pin every client (browser, server, middleware) to the name derived from
NEXT_PUBLIC_SUPABASE_URL via a shared helper so the namespace stays consistent
regardless of which API endpoint the client talks to.
Server-side Supabase calls (middleware getUser/refresh, server components,
admin client) all egress through the Docker gateway as a single NATed IP and
traverse Caddy's per-IP /auth/* rate limiter (8 events/s). A handful of active
users saturate that shared bucket, 429ing getUser()/token refresh; the
middleware then treats the session as invalid and bounces to /login, while a
manual refresh lands under budget and works again.
Add SUPABASE_INTERNAL_URL (e.g. http://kong-prod:8000) used only by the
server-side clients (middleware, lib/supabase/server.ts, admin getSupabaseAdmin
/getSupabaseAnon), falling back to the public URL when unset. Browser clients
keep the public URL so real per-user-IP edge rate limiting still applies.
Also bake the arg in the Dockerfile/build and make the web-prod network alias
durable via WEB_ALIAS (dev sets web-dev) so the dev container can't reclaim the
web-prod alias on redeploy.
Gerhard Scheikl