diff --git a/packages/system/seaweedfs/tests/fullname_override_test.yaml b/packages/system/seaweedfs/tests/fullname_override_test.yaml
new file mode 100644
index 000000000..545e949b5
--- /dev/null
+++ b/packages/system/seaweedfs/tests/fullname_override_test.yaml
@@ -0,0 +1,62 @@
+suite: seaweedfs workload naming is pinned to the chart name
+
+# Upstream chart 4.31 names workloads after the Helm release (`seaweedfs.fullname`)
+# instead of after the chart (`seaweedfs.name`, pre-4.31). The shipped release is
+# `seaweedfs-system`, so the bump silently renamed every StatefulSet/Deployment to
+# `seaweedfs-system-*`. Those names are immutable, so an upgrade cannot rename in
+# place — Helm brings up a second, duplicate set beside the running one while the
+# data stays on the original `data1-seaweedfs-volume-*` PVCs.
+#
+# values.yaml pins `fullnameOverride: seaweedfs` so the rendered names stay
+# chart-based regardless of the release name, matching the convention already used
+# by other system packages (cozy-proxy, flux-operator, linstor-scheduler, ...).
+# These tests pin that contract: names must NOT follow the release name.
+
+release:
+  name: seaweedfs-system
+  namespace: tenant-root
+
+tests:
+  - it: names the master StatefulSet after the chart, not the release
+    template: charts/seaweedfs/templates/master/master-statefulset.yaml
+    asserts:
+      - equal:
+          path: metadata.name
+          value: seaweedfs-master
+      - equal:
+          path: spec.serviceName
+          value: seaweedfs-master
+
+  - it: names the volume StatefulSet after the chart, so its data PVCs keep the legacy names
+    template: charts/seaweedfs/templates/volume/volume-statefulset.yaml
+    asserts:
+      - equal:
+          path: metadata.name
+          value: seaweedfs-volume
+      # Together with the StatefulSet name this yields data1-seaweedfs-volume-N —
+      # the PVC names the running clusters already hold their data on.
+      - equal:
+          path: spec.volumeClaimTemplates[0].metadata.name
+          value: data1
+
+  - it: names the filer StatefulSet after the chart
+    template: charts/seaweedfs/templates/filer/filer-statefulset.yaml
+    asserts:
+      - equal:
+          path: metadata.name
+          value: seaweedfs-filer
+
+  - it: keeps the selector labels release-scoped so adopted pods keep matching
+    template: charts/seaweedfs/templates/master/master-statefulset.yaml
+    asserts:
+      # A StatefulSet selector is immutable: in-place adoption only works because
+      # 4.31 left these labels identical to 4.05.
+      - equal:
+          path: spec.selector.matchLabels["app.kubernetes.io/name"]
+          value: seaweedfs
+      - equal:
+          path: spec.selector.matchLabels["app.kubernetes.io/instance"]
+          value: seaweedfs-system
+      - equal:
+          path: spec.selector.matchLabels["app.kubernetes.io/component"]
+          value: master
diff --git a/packages/system/seaweedfs/tests/s3_service_name_consumers_test.yaml b/packages/system/seaweedfs/tests/s3_service_name_consumers_test.yaml
index 628d2713b..b536b7c57 100644
--- a/packages/system/seaweedfs/tests/s3_service_name_consumers_test.yaml
+++ b/packages/system/seaweedfs/tests/s3_service_name_consumers_test.yaml
@@ -13,9 +13,12 @@ suite: seaweedfs s3 consumers resolve the renamed s3 service
 # `seaweedfs-system-s3` while the real service is `seaweedfs-s3`. With no
 # matching endpoints, ingress-nginx returns 503 and COSI cannot reach S3.
 #
-# All tests render under the real release name so name != fullname, the exact
-# condition that exposes the bug. The all-in-one case documents the other
-# ternary branch, which is unchanged and correct.
+# values.yaml now pins fullnameOverride: seaweedfs, which makes name == fullname
+# and would hide this bug by accident. So each test re-creates the original
+# condition explicitly (fullnameOverride: seaweedfs-system => name != fullname)
+# and keeps guarding the divergence itself, independent of what the shipped
+# default happens to be. The all-in-one case documents the other ternary branch,
+# which is unchanged and correct.
 
 templates:
   - charts/seaweedfs/templates/s3/s3-service.yaml
@@ -31,6 +34,7 @@ tests:
   - it: s3 service is named with the name helper, not componentName
     template: charts/seaweedfs/templates/s3/s3-service.yaml
     set:
+      seaweedfs.fullnameOverride: seaweedfs-system
       seaweedfs.s3.enabled: true
     asserts:
       - equal:
@@ -40,6 +44,7 @@ tests:
   - it: s3 ingress backend points at the s3 service, not a fullname-derived name
     template: charts/seaweedfs/templates/s3/s3-ingress.yaml
     set:
+      seaweedfs.fullnameOverride: seaweedfs-system
       seaweedfs.s3.enabled: true
       seaweedfs.s3.ingress.enabled: true
       seaweedfs.s3.ingress.host: s3.example.com
@@ -51,6 +56,7 @@ tests:
   - it: all-in-one ingress backend still resolves to the all-in-one service
     template: charts/seaweedfs/templates/s3/s3-ingress.yaml
     set:
+      seaweedfs.fullnameOverride: seaweedfs-system
       seaweedfs.allInOne.enabled: true
       seaweedfs.allInOne.s3.enabled: true
       seaweedfs.s3.ingress.enabled: true
@@ -63,6 +69,7 @@ tests:
   - it: iceberg ingress backend points at the s3 service too
     template: charts/seaweedfs/templates/s3/s3-iceberg-ingress.yaml
     set:
+      seaweedfs.fullnameOverride: seaweedfs-system
       seaweedfs.s3.enabled: true
       seaweedfs.s3.icebergPort: 8334
       seaweedfs.s3.icebergIngress.enabled: true
@@ -75,6 +82,7 @@ tests:
   - it: COSI in-cluster ENDPOINT resolves the s3 service when ingress is disabled
     template: charts/seaweedfs/templates/cosi/cosi-deployment.yaml
     set:
+      seaweedfs.fullnameOverride: seaweedfs-system
       seaweedfs.cosi.enabled: true
       seaweedfs.s3.enabled: true
       seaweedfs.s3.ingress.enabled: false
@@ -88,6 +96,7 @@ tests:
   - it: COSI in-cluster ENDPOINT (filer S3 mode) targets the s3 service on the filer s3 port
     template: charts/seaweedfs/templates/cosi/cosi-deployment.yaml
     set:
+      seaweedfs.fullnameOverride: seaweedfs-system
       seaweedfs.cosi.enabled: true
       seaweedfs.s3.enabled: false
       seaweedfs.filer.s3.enabled: true
diff --git a/packages/system/seaweedfs/values.yaml b/packages/system/seaweedfs/values.yaml
index c363dc3ed..ce126b158 100644
--- a/packages/system/seaweedfs/values.yaml
+++ b/packages/system/seaweedfs/values.yaml
@@ -11,6 +11,17 @@ global:
     monitoring:
       enabled: true
 seaweedfs:
+  # Decouple the workload names from the Helm release name. Upstream 4.31 started
+  # naming resources after the release, and the data-plane release is
+  # `<name>-system`, so every StatefulSet was renamed to `<name>-system-*`. Those
+  # names are immutable, so Helm could not rename in place — it stood up a second,
+  # empty set beside the running one while the data stayed on `data1-seaweedfs-volume-*`.
+  # Pinning the chart name restores the pre-4.31 names, so the running workloads
+  # and their volumes are adopted across the bump. extra/seaweedfs does NOT override
+  # this per release — it relies on this pin — and guards the one case the pin
+  # cannot serve (a tenant installed fresh on 1.5.x, whose data is on the renamed
+  # volumes) by refusing to render.
+  fullnameOverride: seaweedfs
   master:
     # 30 GB per volume × 10 GiB PVC = 0 → rounded to 1 maxVolume per
     # volume server. With defaultReplication=001 (one replica on a