diff --git a/weed/operation/assign_file_id.go b/weed/operation/assign_file_id.go
index bddc1ae9c..4fb258158 100644
--- a/weed/operation/assign_file_id.go
+++ b/weed/operation/assign_file_id.go
@@ -193,12 +193,20 @@ type StorageOption struct {
 	MaxFileNameLength uint32
 	Fsync             bool
 	SaveInside        bool
+	// EnforceLocation marks a location that came from a placement rule or an
+	// explicit request rather than a filer-level default: it must fail the
+	// assign when unsatisfiable instead of widening to anywhere.
+	EnforceLocation bool
 }
 
 func (so *StorageOption) TtlString() string {
 	return needle.SecondsToTTL(so.TtlSeconds)
 }
 
+// ToAssignRequests builds the assign request for this storage option. When the
+// location came from a filer-level default rather than a placement rule or an
+// explicit request, it also returns a location-stripped fallback for the case
+// where the preferred location cannot serve the write at all.
 func (so *StorageOption) ToAssignRequests(count int) (ar *VolumeAssignRequest, altRequest *VolumeAssignRequest) {
 	ar = &VolumeAssignRequest{
 		Count:               uint64(count),
@@ -211,16 +219,13 @@ func (so *StorageOption) ToAssignRequests(count int) (ar *VolumeAssignRequest, a
 		DataNode:            so.DataNode,
 		WritableVolumeCount: so.VolumeGrowthCount,
 	}
-	if so.DataCenter != "" || so.Rack != "" || so.DataNode != "" {
+	if !so.EnforceLocation && (so.DataCenter != "" || so.Rack != "" || so.DataNode != "") {
 		altRequest = &VolumeAssignRequest{
 			Count:               uint64(count),
 			Replication:         so.Replication,
 			Collection:          so.Collection,
 			Ttl:                 so.TtlString(),
 			DiskType:            so.DiskType,
-			DataCenter:          "",
-			Rack:                "",
-			DataNode:            "",
 			WritableVolumeCount: so.VolumeGrowthCount,
 		}
 	}
diff --git a/weed/operation/assign_file_id_test.go b/weed/operation/assign_file_id_test.go
new file mode 100644
index 000000000..e14327d8e
--- /dev/null
+++ b/weed/operation/assign_file_id_test.go
@@ -0,0 +1,42 @@
+package operation
+
+import "testing"
+
+// An enforced location on a storage option is a placement contract: the assign
+// request must carry it, and no widened fallback may follow it.
+func TestToAssignRequestsKeepsEnforcedLocation(t *testing.T) {
+	so := &StorageOption{
+		Collection:      "dump",
+		Rack:            "l1000",
+		DataCenter:      "dc1",
+		EnforceLocation: true,
+	}
+	ar, alt := so.ToAssignRequests(1)
+	if ar.DataCenter != "dc1" || ar.Rack != "l1000" {
+		t.Fatalf("expected the rule's location, got dc=%q rack=%q", ar.DataCenter, ar.Rack)
+	}
+	if alt != nil {
+		t.Fatalf("enforced location must not be widened, got alt dc=%q rack=%q", alt.DataCenter, alt.Rack)
+	}
+}
+
+// A filer-level default location is a preference: the request still carries
+// it, and a location-stripped fallback follows so a preferred but unservable
+// location does not fail the write.
+func TestToAssignRequestsWidensDefaultLocation(t *testing.T) {
+	so := &StorageOption{
+		Collection: "dump",
+		Rack:       "l1000",
+		DataCenter: "dc1",
+	}
+	ar, alt := so.ToAssignRequests(1)
+	if ar.DataCenter != "dc1" || ar.Rack != "l1000" {
+		t.Fatalf("expected the preferred location, got dc=%q rack=%q", ar.DataCenter, ar.Rack)
+	}
+	if alt == nil || alt.DataCenter != "" || alt.Rack != "" {
+		t.Fatalf("default location should keep a widened fallback, got %+v", alt)
+	}
+	if alt.Collection != "dump" || alt.Replication != ar.Replication {
+		t.Fatalf("fallback must preserve the rest of the option, got %+v", alt)
+	}
+}
diff --git a/weed/server/filer_grpc_server_sub_meta.go b/weed/server/filer_grpc_server_sub_meta.go
index 387024a7d..9db11ec09 100644
--- a/weed/server/filer_grpc_server_sub_meta.go
+++ b/weed/server/filer_grpc_server_sub_meta.go
@@ -772,11 +772,11 @@ func (fs *FilerServer) SubscribeMetadata(req *filer_pb.SubscribeMetadataRequest,
 	var readPersistedLogErr error
 	var readInMemoryLogErr error
 	var isDone bool
-	var lastCheckedFlushTsNs int64 = -1      // Track the last local flush we read the disk under
-	var lastCheckedFlushLowTsNs int64 = -1   // Track the last peer flush low-watermark we read the disk under
-	var lastDiskReadTsNs int64 = -1          // Track the last read position we used for disk read
-	var lastDiskRefsStopTsNs int64 = -1      // Track the last chunk listing bound we read the disk under
-	var lastDiskPassAt time.Time             // Paces re-probes for files no watermark signals
+	var lastCheckedFlushTsNs int64 = -1    // Track the last local flush we read the disk under
+	var lastCheckedFlushLowTsNs int64 = -1 // Track the last peer flush low-watermark we read the disk under
+	var lastDiskReadTsNs int64 = -1        // Track the last read position we used for disk read
+	var lastDiskRefsStopTsNs int64 = -1    // Track the last chunk listing bound we read the disk under
+	var lastDiskPassAt time.Time           // Paces re-probes for files no watermark signals
 	sentRefs := make(map[string]sentRefState)
 
 	aggBuffer := fs.filer.MetaAggregator.MetaLogBuffer
diff --git a/weed/server/filer_server_handlers_write.go b/weed/server/filer_server_handlers_write.go
index 4bb91c9d0..0864409c3 100644
--- a/weed/server/filer_server_handlers_write.go
+++ b/weed/server/filer_server_handlers_write.go
@@ -335,6 +335,11 @@ func (fs *FilerServer) detectStorageOption(ctx context.Context, requestURI, qCol
 		Fsync:             rule.Fsync,
 		VolumeGrowthCount: rule.VolumeGrowthCount,
 		MaxFileNameLength: maxFileNameLength,
+		// A location that survives from a request parameter, a placement
+		// overlay, or the path rule is a contract; only a bare filer default
+		// is a preference that may still be widened.
+		EnforceLocation: dataCenter != "" || overlayDataCenter != "" || rule.DataCenter != "" ||
+			rack != "" || rule.Rack != "" || dataNode != "" || rule.DataNode != "",
 	}, nil
 }