diff --git a/server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamLifecycle.java b/server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamLifecycle.java
index 042debf848566..5a0699dbf07bd 100644
--- a/server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamLifecycle.java
+++ b/server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamLifecycle.java
@@ -383,8 +383,7 @@ public void writeTo(StreamOutput out) throws IOException {
         if (out.getTransportVersion().supports(ADD_SAMPLE_METHOD_DOWNSAMPLE_DLM)) {
             out.writeOptionalWriteable(downsamplingMethod);
         }
-        if (out.getTransportVersion().supports(DLM_FROZEN_TIER_GA_TV)
-            || (DLM_SEARCHABLE_SNAPSHOTS_FEATURE_FLAG.isEnabled() && out.getTransportVersion().supports(SEARCHABLE_SNAPSHOTS_DLM_TV))) {
+        if (out.getTransportVersion().supports(DLM_FROZEN_TIER_GA_TV) || out.getTransportVersion().supports(SEARCHABLE_SNAPSHOTS_DLM_TV)) {
             out.writeOptionalTimeValue(frozenAfter);
         }
     }
@@ -405,8 +404,11 @@ public DataStreamLifecycle(StreamInput in) throws IOException {
         downsamplingMethod = in.getTransportVersion().supports(ADD_SAMPLE_METHOD_DOWNSAMPLE_DLM)
             ? in.readOptionalWriteable(DownsampleConfig.SamplingMethod::read)
             : null;
-        frozenAfter = ((DLM_SEARCHABLE_SNAPSHOTS_FEATURE_FLAG.isEnabled() && in.getTransportVersion().supports(SEARCHABLE_SNAPSHOTS_DLM_TV))
-            || in.getTransportVersion().supports(DLM_FROZEN_TIER_GA_TV)) ? in.readOptionalTimeValue() : null;
+        if (in.getTransportVersion().supports(SEARCHABLE_SNAPSHOTS_DLM_TV) || in.getTransportVersion().supports(DLM_FROZEN_TIER_GA_TV)) {
+            frozenAfter = in.readOptionalTimeValue();
+        } else {
+            frozenAfter = null;
+        }
     }
 
     /**
@@ -790,8 +792,8 @@ public void writeTo(StreamOutput out) throws IOException {
             if (out.getTransportVersion().supports(ADD_SAMPLE_METHOD_DOWNSAMPLE_DLM)) {
                 ResettableValue.write(out, downsamplingMethod, StreamOutput::writeWriteable);
             }
-            if ((DLM_SEARCHABLE_SNAPSHOTS_FEATURE_FLAG.isEnabled() && out.getTransportVersion().supports(SEARCHABLE_SNAPSHOTS_DLM_TV)
-                || out.getTransportVersion().supports(DLM_FROZEN_TIER_GA_TV))) {
+            if (out.getTransportVersion().supports(SEARCHABLE_SNAPSHOTS_DLM_TV)
+                || out.getTransportVersion().supports(DLM_FROZEN_TIER_GA_TV)) {
                 ResettableValue.write(out, frozenAfter, StreamOutput::writeTimeValue);
             }
         }
@@ -854,9 +856,8 @@ public static Template read(StreamInput in) throws IOException {
                 .supports(ADD_SAMPLE_METHOD_DOWNSAMPLE_DLM)
                     ? ResettableValue.read(in, DownsampleConfig.SamplingMethod::read)
                     : ResettableValue.undefined();
-            ResettableValue<TimeValue> frozenAfter = (DLM_SEARCHABLE_SNAPSHOTS_FEATURE_FLAG.isEnabled()
-                && in.getTransportVersion().supports(SEARCHABLE_SNAPSHOTS_DLM_TV)
-                || in.getTransportVersion().supports(DLM_FROZEN_TIER_GA_TV))
+            ResettableValue<TimeValue> frozenAfter = in.getTransportVersion().supports(SEARCHABLE_SNAPSHOTS_DLM_TV)
+                || in.getTransportVersion().supports(DLM_FROZEN_TIER_GA_TV)
                     ? ResettableValue.read(in, StreamInput::readTimeValue)
                     : ResettableValue.undefined();
             return new Template(lifecycleTarget, enabled, dataRetention, downsamplingRounds, downsamplingMethod, frozenAfter);
diff --git a/x-pack/plugin/esql/qa/server/mixed-cluster/src/javaRestTest/java/org/elasticsearch/xpack/esql/qa/mixed/Clusters.java b/x-pack/plugin/esql/qa/server/mixed-cluster/src/javaRestTest/java/org/elasticsearch/xpack/esql/qa/mixed/Clusters.java
index aa1804d15e31e..ac1d6015ebaa2 100644
--- a/x-pack/plugin/esql/qa/server/mixed-cluster/src/javaRestTest/java/org/elasticsearch/xpack/esql/qa/mixed/Clusters.java
+++ b/x-pack/plugin/esql/qa/server/mixed-cluster/src/javaRestTest/java/org/elasticsearch/xpack/esql/qa/mixed/Clusters.java
@@ -37,11 +37,7 @@ public static ElasticsearchCluster mixedVersionCluster(Path csvDataPath, boolean
             .configFile("ingest-geoip/GeoLite2-City.mmdb", Resource.fromClasspath("GeoLite2-City.mmdb"))
             .configFile("ingest-geoip/GeoLite2-Country.mmdb", Resource.fromClasspath("GeoLite2-Country.mmdb"))
             .configFile("ingest-geoip/GeoLite2-ASN.mmdb", Resource.fromClasspath("GeoLite2-ASN.mmdb"))
-            .setting("ingest.geoip.downloader.enabled", "false")
-            // DLM frozen tier serialization is gated on both a feature flag and a transport version, so nodes in a mixed cluster can
-            // disagree on the wire format when their build types differ (snapshot vs release). Disable the flag on every node so
-            // serialization is consistent regardless of build type. See https://github.com/elastic/elasticsearch/issues/153679.
-            .systemProperty("es.dlm_searchable_snapshots_feature_flag_enabled", "false");
+            .setting("ingest.geoip.downloader.enabled", "false");
         if (supportRetryOnShardFailures(oldVersion) == false) {
             cluster.setting("cluster.routing.rebalance.enable", "none");
         }