diff --git a/docker-compose.yml b/docker-compose.yml
index 843a208..f13733a 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -386,6 +386,8 @@ services:
     image: prom/blackbox-exporter:latest
     volumes:
       - ./monitoring/blackbox.yml:/etc/blackbox_exporter/config.yml:ro
+    extra_hosts:
+      - "host.docker.internal:host-gateway"
     restart: unless-stopped
 
 volumes:
diff --git a/monitoring/blackbox.yml b/monitoring/blackbox.yml
index 2ceee14..7eed68e 100644
--- a/monitoring/blackbox.yml
+++ b/monitoring/blackbox.yml
@@ -20,6 +20,17 @@ modules:
       follow_redirects: false
       preferred_ip_protocol: ip4
 
+  # ERPNext requires Host header matching the site name
+  http_erpnext:
+    prober: http
+    timeout: 10s
+    http:
+      valid_http_versions: ["HTTP/1.1", "HTTP/2.0"]
+      valid_status_codes: [200]
+      headers:
+        Host: performancewest.net
+      preferred_ip_protocol: ip4
+
   tcp_connect:
     prober: tcp
     timeout: 5s
diff --git a/monitoring/prometheus.yml b/monitoring/prometheus.yml
index d2bb381..2287a86 100644
--- a/monitoring/prometheus.yml
+++ b/monitoring/prometheus.yml
@@ -125,11 +125,11 @@ scrape_configs:
       - target_label: __address__
         replacement: blackbox-exporter:9115
 
-  # ── ERPNext CRM (login page returns 200) ───────────────────────────
+  # ── ERPNext CRM (requires Host header for site routing) ─────────────
   - job_name: pw_erpnext
     metrics_path: /probe
     params:
-      module: [http_internal]
+      module: [http_erpnext]
     static_configs:
       - targets:
           - http://erpnext:8000/api/method/ping