fix(auth): route server-side Supabase calls via internal URL to avoid edge rate-limit

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.

Dockerfile

@@ -15,9 +15,14 @@ COPY . .
 ARG NEXT_PUBLIC_SUPABASE_URL
 ARG NEXT_PUBLIC_SUPABASE_ANON_KEY
 ARG NEXT_PUBLIC_APP_URL
+# Server-only internal Supabase URL (e.g. http://kong-prod:8000). Provided at
+# build time so Next inlines it into the Edge middleware bundle; also read at
+# runtime by the Node server components. Optional — falls back to the public URL.
+ARG SUPABASE_INTERNAL_URL
 ENV NEXT_PUBLIC_SUPABASE_URL=$NEXT_PUBLIC_SUPABASE_URL \
     NEXT_PUBLIC_SUPABASE_ANON_KEY=$NEXT_PUBLIC_SUPABASE_ANON_KEY \
-    NEXT_PUBLIC_APP_URL=$NEXT_PUBLIC_APP_URL
+    NEXT_PUBLIC_APP_URL=$NEXT_PUBLIC_APP_URL \
+    SUPABASE_INTERNAL_URL=$SUPABASE_INTERNAL_URL
 RUN npm run build
 
 FROM node:24.16.0-alpine AS runner

docker-compose.yml

@@ -4,7 +4,8 @@
 # supplied via env vars resolved from the project-dir ".env" file
 # (in prod and dev that is a symlink -> .env.production). The defaults below are
 # the PRODUCTION values, so prod works with no extra vars; the dev worktree's
-# .env.production sets WEB_PROJECT / WEB_IMAGE / WEB_CONTAINER / WEB_NETWORK.
+# .env.production sets WEB_PROJECT / WEB_IMAGE / WEB_CONTAINER / WEB_NETWORK /
+# WEB_ALIAS (and SUPABASE_INTERNAL_URL for the internal API hostname).
 name: ${WEB_PROJECT:-web}
 services:
   web:
@@ -15,6 +16,7 @@ services:
         NEXT_PUBLIC_SUPABASE_URL: ${NEXT_PUBLIC_SUPABASE_URL}
         NEXT_PUBLIC_SUPABASE_ANON_KEY: ${NEXT_PUBLIC_SUPABASE_ANON_KEY}
         NEXT_PUBLIC_APP_URL: ${NEXT_PUBLIC_APP_URL}
+        SUPABASE_INTERNAL_URL: ${SUPABASE_INTERNAL_URL:-}
     image: ${WEB_IMAGE:-web:1.0.0}
     container_name: ${WEB_CONTAINER:-web}
     restart: unless-stopped
@@ -29,6 +31,9 @@ services:
     networks:
       default:
         aliases:
+          # PROD defaults to web-prod; dev's .env.production sets WEB_ALIAS=web-dev
+          # so the dev container does NOT also claim the web-prod alias (which
+          # would make Caddy round-robin prod traffic onto the dev build).
           - ${WEB_ALIAS:-web-prod}
     healthcheck:
       test: ["CMD", "wget", "-qO-", "http://127.0.0.1:3000/"]

lib/supabase/admin.ts

@@ -33,7 +33,10 @@ const adminDispatcher = new Agent({
 
 export function getSupabaseAdmin(): SupabaseClient {
   if (_admin) return _admin;
-  const url = process.env.NEXT_PUBLIC_SUPABASE_URL;
+  // Reach Supabase over the internal Docker network when configured, bypassing
+  // the Caddy edge/rate limiter; fall back to the public URL otherwise.
+  const url =
+    process.env.SUPABASE_INTERNAL_URL ?? process.env.NEXT_PUBLIC_SUPABASE_URL;
   const key = process.env.SUPABASE_SERVICE_ROLE_KEY;
   if (!url || !key) {
     throw new Error('Supabase admin env not configured');
@@ -57,7 +60,9 @@ export function getSupabaseAdmin(): SupabaseClient {
 }
 
 export function getSupabaseAnon(): SupabaseClient {
-  const url = process.env.NEXT_PUBLIC_SUPABASE_URL;
+  // Server-side anon client also prefers the internal Docker URL.
+  const url =
+    process.env.SUPABASE_INTERNAL_URL ?? process.env.NEXT_PUBLIC_SUPABASE_URL;
   const key = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY;
   if (!url || !key) {
     throw new Error('Supabase anon env not configured');

lib/supabase/server.ts

@@ -4,7 +4,9 @@ import { cookies } from 'next/headers';
 export function createSupabaseServerClient() {
   const cookieStore = cookies();
   return createServerClient(
-    process.env.NEXT_PUBLIC_SUPABASE_URL!,
+    // Prefer the internal Docker URL so server-side calls skip the Caddy edge
+    // (and its rate limiter); fall back to the public URL when unset.
+    process.env.SUPABASE_INTERNAL_URL ?? process.env.NEXT_PUBLIC_SUPABASE_URL!,
     process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
     {
       cookies: {

middleware.ts

@@ -25,7 +25,13 @@ export async function middleware(request: NextRequest) {
   let response = NextResponse.next({ request });
 
   const supabase = createServerClient(
-    process.env.NEXT_PUBLIC_SUPABASE_URL!,
+    // Server-side requests reach Supabase directly over the Docker network
+    // (SUPABASE_INTERNAL_URL, e.g. http://kong-prod:8000) so they bypass
+    // Caddy's per-IP `/auth/*` rate limiter; all server traffic would
+    // otherwise share a single NATed gateway IP and saturate that budget,
+    // intermittently 429ing getUser() and bouncing users to /login. Falls
+    // back to the public URL when the internal one is not configured.
+    process.env.SUPABASE_INTERNAL_URL ?? process.env.NEXT_PUBLIC_SUPABASE_URL!,
     process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
     {
       cookies: {