diff --git a/deploy/nginx-m1.conf b/deploy/nginx-m1.conf
index 7a28f6c..43e3a6c 100644
--- a/deploy/nginx-m1.conf
+++ b/deploy/nginx-m1.conf
@@ -4,6 +4,11 @@ server {
     root /usr/share/nginx/html;
     index index.html;
 
+    # Capture→Review uploads the calibrated lineup PNGs (clean cal + batch) as
+    # multipart to /api/v1/slabs/{id}/photos. nginx's default client_max_body_size
+    # is 1MB, which 413s on real multi-MB photos. Allow large photo bodies.
+    client_max_body_size 25m;
+
     # Docker embedded DNS for service name resolution (fastapi)
     resolver 127.0.0.11 valid=10s;