diff --git a/k8s/bases/infrastructure/cluster-policies/best-practices/restrict-doggy-countdown-hostnames.yaml b/k8s/bases/infrastructure/cluster-policies/best-practices/restrict-doggy-countdown-hostnames.yaml
new file mode 100644
index 000000000..4db51bc83
--- /dev/null
+++ b/k8s/bases/infrastructure/cluster-policies/best-practices/restrict-doggy-countdown-hostnames.yaml
@@ -0,0 +1,43 @@
+# The doggy-countdown deployment is sourced from a separately published OCI
+# artifact and is applied as a ServiceAccount with permission to manage
+# HTTPRoutes in this namespace. Keep that publishing path from claiming another
+# hostname on the shared, cross-namespace Gateway (and from making external-dns
+# publish that claim). Requiring exactly one hostname also rejects a hostname-
+# less route, which Gateway API would otherwise match against every hostname.
+apiVersion: kyverno.io/v1
+kind: ClusterPolicy
+metadata:
+  name: restrict-doggy-countdown-hostnames
+  annotations:
+    policies.kyverno.io/title: Restrict Doggy Countdown Hostnames
+    policies.kyverno.io/category: Security, Gateway API
+    policies.kyverno.io/severity: high
+    policies.kyverno.io/subject: HTTPRoute
+    policies.kyverno.io/minversion: 1.6.0
+    policies.kyverno.io/description: >-
+      Restricts HTTPRoutes in the doggy-countdown namespace to the tenant's
+      assigned simba hostname so its remote manifest source cannot claim other
+      names on the shared platform Gateway.
+spec:
+  validationFailureAction: Enforce
+  background: true
+  rules:
+    - name: require-doggy-countdown-hostname
+      match:
+        any:
+          - resources:
+              kinds:
+                - HTTPRoute
+              namespaces:
+                - doggy-countdown
+      validate:
+        message: >-
+          Doggy countdown HTTPRoutes must declare exactly one hostname:
+          simba.${domain}.
+        deny:
+          conditions:
+            any:
+              - key: "{{ request.object.spec.hostnames || `[]` }}"
+                operator: NotEquals
+                value:
+                  - "simba.${domain}"
diff --git a/k8s/bases/infrastructure/cluster-policies/kustomization.yaml b/k8s/bases/infrastructure/cluster-policies/kustomization.yaml
index 381a7b082..ed7580fe6 100644
--- a/k8s/bases/infrastructure/cluster-policies/kustomization.yaml
+++ b/k8s/bases/infrastructure/cluster-policies/kustomization.yaml
@@ -12,6 +12,7 @@ resources:
   - best-practices/disable-default-sa-automount.yaml
   - best-practices/disallow-latest-tag.yaml
   - best-practices/propagate-reloader-to-flagger-primary.yaml
+  - best-practices/restrict-doggy-countdown-hostnames.yaml
   - best-practices/restrict-tenant-secret-stores.yaml
   - best-practices/validate-host-restrictions.yaml
   - best-practices/validate-pdb-drain-safe.yaml
diff --git a/tests/restrict-doggy-countdown-hostnames/kyverno-test.yaml b/tests/restrict-doggy-countdown-hostnames/kyverno-test.yaml
new file mode 100644
index 000000000..c395bad7b
--- /dev/null
+++ b/tests/restrict-doggy-countdown-hostnames/kyverno-test.yaml
@@ -0,0 +1,31 @@
+---
+apiVersion: cli.kyverno.io/v1alpha1
+kind: Test
+metadata:
+  name: restrict-doggy-countdown-hostnames
+policies:
+  - >-
+    ../../k8s/bases/infrastructure/cluster-policies/best-practices/restrict-doggy-countdown-hostnames.yaml
+resources:
+  - resources.yaml
+results:
+  - policy: restrict-doggy-countdown-hostnames
+    rule: require-doggy-countdown-hostname
+    resources:
+      - doggy-countdown/intended-hostname
+    kind: HTTPRoute
+    result: pass
+  - policy: restrict-doggy-countdown-hostnames
+    rule: require-doggy-countdown-hostname
+    resources:
+      - doggy-countdown/arbitrary-hostname
+      - doggy-countdown/hostname-less
+      - doggy-countdown/mixed-hostnames
+    kind: HTTPRoute
+    result: fail
+  - policy: restrict-doggy-countdown-hostnames
+    rule: require-doggy-countdown-hostname
+    resources:
+      - another-tenant/arbitrary-hostname
+    kind: HTTPRoute
+    result: skip
diff --git a/tests/restrict-doggy-countdown-hostnames/resources.yaml b/tests/restrict-doggy-countdown-hostnames/resources.yaml
new file mode 100644
index 000000000..44f35d107
--- /dev/null
+++ b/tests/restrict-doggy-countdown-hostnames/resources.yaml
@@ -0,0 +1,44 @@
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: HTTPRoute
+metadata:
+  name: intended-hostname
+  namespace: doggy-countdown
+spec:
+  hostnames:
+    - "simba.${domain}"
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: HTTPRoute
+metadata:
+  name: arbitrary-hostname
+  namespace: doggy-countdown
+spec:
+  hostnames:
+    - login.platform.devantler.tech
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: HTTPRoute
+metadata:
+  name: hostname-less
+  namespace: doggy-countdown
+spec: {}
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: HTTPRoute
+metadata:
+  name: mixed-hostnames
+  namespace: doggy-countdown
+spec:
+  hostnames:
+    - "simba.${domain}"
+    - login.platform.devantler.tech
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: HTTPRoute
+metadata:
+  name: arbitrary-hostname
+  namespace: another-tenant
+spec:
+  hostnames:
+    - login.platform.devantler.tech