diff --git a/frontend/nginx.conf b/frontend/nginx.conf
index 96a390a..e3f8d02 100644
--- a/frontend/nginx.conf
+++ b/frontend/nginx.conf
@@ -14,8 +14,15 @@ server {
     client_max_body_size 50m;
 
     # API reverse proxy -> FastAPI backend (port 8000)
+    # NOTE: upstream is resolved at REQUEST time through Docker's embedded DNS
+    # (127.0.0.11). A plain `proxy_pass http://api:8000` caches the container
+    # IP at nginx startup, so after the api container restarts and gets a new
+    # IP, nginx keeps proxying to the stale address (which may belong to
+    # another service) until this container is restarted too.
     location /api/ {
-        proxy_pass http://api:8000;
+        resolver 127.0.0.11 valid=10s ipv6=off;
+        set $api_upstream http://api:8000;
+        proxy_pass $api_upstream;
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;