diff --git a/.github/workflows/helm-test.yml b/.github/workflows/helm-test.yml
index 1e4b80e5b7..04ae27a9e6 100644
--- a/.github/workflows/helm-test.yml
+++ b/.github/workflows/helm-test.yml
@@ -179,6 +179,29 @@ jobs:
 
           fail() { echo "::error::$1"; exit 1; }
 
+          # Without a Namespace in the render, Argo's CreateNamespace=true creates
+          # one it never adopts: everything inside is deleted correctly and the
+          # namespace itself is left behind, one per PR, forever.
+          grep -q '^kind: Namespace' /tmp/preview.yaml \
+            || fail "preview render has no Namespace — it would outlive the PR"
+          python3 - <<'NS'
+          import sys, yaml
+          ns = [d for d in yaml.safe_load_all(open("/tmp/preview.yaml"))
+                if d and d["kind"] == "Namespace"]
+          if len(ns) != 1:
+              print(f"::error::expected exactly one Namespace, found {len(ns)}"); sys.exit(1)
+          m = ns[0]["metadata"]
+          w = int((m.get("annotations") or {}).get("argocd.argoproj.io/sync-wave", 0))
+          if w >= -30:
+              print(f"::error::Namespace is at wave {w}, but everything lives inside it "
+                    "— it must come before the ExternalSecret at -30"); sys.exit(1)
+          if not any(k.endswith("/preview") for k in (m.get("labels") or {})):
+              print("::error::Namespace carries no preview label — the Gateway admits "
+                    "routes by namespace label, so the HTTPRoute would attach to nothing")
+              sys.exit(1)
+          print(f"namespace rendered at wave {w} with the gateway selector label")
+          NS
+
           grep -q 'kind: HTTPRoute' /tmp/preview.yaml \
             || fail "preview render has no HTTPRoute — the preview would be unreachable"
           grep -q 'pr-42.pr.studio.decocms.com' /tmp/preview.yaml \
diff --git a/deploy/helm/studio-previews/templates/applicationset.yaml b/deploy/helm/studio-previews/templates/applicationset.yaml
index 0db0c63053..6dfaf11a7f 100644
--- a/deploy/helm/studio-previews/templates/applicationset.yaml
+++ b/deploy/helm/studio-previews/templates/applicationset.yaml
@@ -64,6 +64,13 @@ spec:
                   tag: '{{ include "studio-previews.imageTag" . }}'
               preview:
                 prNumber: '{{ `{{ .number }}` }}'
+                # The chart renders the namespace itself, so the label the
+                # Gateway selects on travels with the manifest instead of
+                # depending on managedNamespaceMetadata below. Both are set:
+                # the metadata still labels the namespace on the first sync,
+                # before the chart's own object is applied.
+                namespaceLabels:
+                  {{ .Values.gateway.namespaceSelectorLabel }}: "true"
                 host: '{{ include "studio-previews.host" . }}'
                 gateway:
                   name: {{ .Values.gateway.name }}
diff --git a/deploy/helm/studio/Chart.yaml b/deploy/helm/studio/Chart.yaml
index bb5b01487e..2819c88d7e 100644
--- a/deploy/helm/studio/Chart.yaml
+++ b/deploy/helm/studio/Chart.yaml
@@ -2,6 +2,12 @@ apiVersion: v2
 name: chart-deco-studio
 description: Helm chart for deco Studio — supports inline secrets, external secretName, and AWS Secrets Manager via ExternalSecret
 type: application
+# 0.14.3: the preview renders its own Namespace (preview.manageNamespace).
+# CreateNamespace=true creates one without adopting it, so a cascading delete
+# removed everything inside and left the namespace behind — one per pull request
+# that ever had a preview. It also carries the Gateway's selector label now, so
+# route attachment no longer depends on managedNamespaceMetadata.
+#
 # 0.14.2: optional hosted sandboxes for previews (preview.sandbox.enabled,
 # default false). Renders one RoleBinding when on, nothing when off. Read the
 # note in templates/preview-sandbox-rbac.yaml before enabling: the namespace it
@@ -32,7 +38,7 @@ type: application
 # when disabled, so existing releases are unaffected.
 # 0.12.4: chart-managed API/worker dispatch roles now use
 # STUDIO_DISPATCH_ROLE; legacy overrides are rejected.
-version: 0.14.2
+version: 0.14.3
 appVersion: "latest"
 
 dependencies:
diff --git a/deploy/helm/studio/templates/preview-namespace.yaml b/deploy/helm/studio/templates/preview-namespace.yaml
new file mode 100644
index 0000000000..530f63bbbf
--- /dev/null
+++ b/deploy/helm/studio/templates/preview-namespace.yaml
@@ -0,0 +1,31 @@
+{{- if and .Values.preview.enabled .Values.preview.manageNamespace }}
+{{- /*
+The preview's own namespace, rendered by the chart rather than conjured by
+Argo's CreateNamespace=true.
+
+CreateNamespace=true creates a namespace but does not adopt it: the object gets
+no tracking annotation and never joins the Application's resource tree, so a
+cascading delete leaves it behind. Everything inside is removed correctly — pods,
+Services, HTTPRoute, ConfigMaps, the Postgres and MinIO that hold the data — and
+an empty namespace stays for every pull request that ever had a preview.
+
+Rendering it here puts it under the same ownership as everything else, so it is
+deleted with them. It also carries its own labels, which means the Gateway's
+namespace selector no longer depends on managedNamespaceMetadata being set
+correctly by whatever creates the Application — the failure that produces a
+silent 404 with a green Argo.
+
+Wave -40: before the ExternalSecret at -30, since everything else is inside it.
+*/ -}}
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: {{ .Release.Namespace }}
+  labels:
+    {{- include "chart-deco-studio.labels" . | nindent 4 }}
+    {{- with .Values.preview.namespaceLabels }}
+    {{- toYaml . | nindent 4 }}
+    {{- end }}
+  annotations:
+    argocd.argoproj.io/sync-wave: "-40"
+{{- end }}
diff --git a/deploy/helm/studio/values-preview.yaml b/deploy/helm/studio/values-preview.yaml
index be70e0497e..0e221df1b6 100644
--- a/deploy/helm/studio/values-preview.yaml
+++ b/deploy/helm/studio/values-preview.yaml
@@ -24,6 +24,8 @@
 
 preview:
   enabled: true
+  # namespaceLabels is injected by the studio-previews ApplicationSet — it is
+  # the one that knows which label the Gateway selects on.
   # prNumber / host injected per PR by the ApplicationSet.
   gateway:
     name: studio-preview
diff --git a/deploy/helm/studio/values.yaml b/deploy/helm/studio/values.yaml
index 5cc3bb7af2..8f171023c0 100644
--- a/deploy/helm/studio/values.yaml
+++ b/deploy/helm/studio/values.yaml
@@ -147,6 +147,21 @@ preview:
       limits:
         memory: "768Mi"
 
+  # Render the preview's namespace as part of the release.
+  #
+  # Argo's CreateNamespace=true creates a namespace without adopting it: no
+  # tracking annotation, never in the Application's resource tree, so a
+  # cascading delete leaves it behind. Everything inside is removed correctly,
+  # and an empty namespace accumulates for every PR that ever had a preview.
+  #
+  # Set false when something else owns the namespace.
+  manageNamespace: true
+  # Labels the namespace carries. The Gateway admits routes by namespace label,
+  # so this is what makes the HTTPRoute attach — putting it here means it no
+  # longer depends on the Application being created with the matching
+  # managedNamespaceMetadata, which is the omission that yields a silent 404.
+  namespaceLabels: {}
+
   # Hosted agent sandboxes for a preview. OFF by default, and it should stay off
   # unless someone is actively testing agent behaviour.
   #