diff --git a/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventAction.java b/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventAction.java
index d92b80f5ca58d..bb041de9fa9fc 100644
--- a/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventAction.java
+++ b/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventAction.java
@@ -22,6 +22,7 @@
 import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.xcontent.ConstructingObjectParser;
 import org.elasticsearch.xcontent.ParseField;
+import org.elasticsearch.xcontent.ToXContentObject;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.XContentParser;
 import org.elasticsearch.xcontent.XContentType;
@@ -47,7 +48,7 @@ private PostAnalyticsEventAction() {
         super(NAME, Response::readFromStreamInput);
     }
 
-    public static class Request extends ActionRequest implements AnalyticsEvent.Context {
+    public static class Request extends ActionRequest implements AnalyticsEvent.Context, ToXContentObject {
 
         private final String eventCollectionName;
 
@@ -199,7 +200,7 @@ public boolean equals(Object o) {
                 && debug == that.debug
                 && eventTime == that.eventTime
                 && Objects.equals(eventType, that.eventType)
-                && Objects.equals(xContentType, that.xContentType)
+                && Objects.equals(xContentType.canonical(), that.xContentType.canonical())
                 && Objects.equals(payload, that.payload)
                 && Objects.equals(headers, that.headers)
                 && Objects.equals(clientAddress, that.clientAddress);
@@ -207,7 +208,36 @@ public boolean equals(Object o) {
 
         @Override
         public int hashCode() {
-            return Objects.hash(eventCollectionName, eventType, debug, eventTime, xContentType, payload, headers, clientAddress);
+            return Objects.hash(
+                eventCollectionName,
+                eventType,
+                debug,
+                eventTime,
+                xContentType.canonical(),
+                payload,
+                headers,
+                clientAddress
+            );
+        }
+
+        @Override
+        public String toString() {
+            return Strings.toString(this);
+        }
+
+        @Override
+        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+            builder.startObject();
+            builder.field("event_collection_name", eventCollectionName);
+            builder.field("debug", debug);
+            builder.field("event_time", eventTime);
+            builder.field("event_type", eventType);
+            builder.field("x_content_type", xContentType);
+            builder.field("payload", payload);
+            builder.field("headers", headers);
+            builder.field("client_address", clientAddress);
+            builder.endObject();
+            return builder;
         }
     }
 
diff --git a/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/search/SearchApplicationListItem.java b/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/search/SearchApplicationListItem.java
index b998d6770f12c..1354f956a51fd 100644
--- a/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/search/SearchApplicationListItem.java
+++ b/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/search/SearchApplicationListItem.java
@@ -11,14 +11,20 @@
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.core.Nullable;
+import org.elasticsearch.xcontent.ConstructingObjectParser;
 import org.elasticsearch.xcontent.ParseField;
 import org.elasticsearch.xcontent.ToXContentObject;
 import org.elasticsearch.xcontent.XContentBuilder;
+import org.elasticsearch.xcontent.XContentParser;
 
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.List;
 import java.util.Objects;
 
+import static org.elasticsearch.xcontent.ConstructingObjectParser.constructorArg;
+import static org.elasticsearch.xcontent.ConstructingObjectParser.optionalConstructorArg;
+
 /**
  * This class is used for returning information for lists of search applications, to avoid including all
  * {@link SearchApplication} information which can be retrieved using subsequent Get Search Application requests.
@@ -75,6 +81,30 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         return builder;
     }
 
+    private static final ConstructingObjectParser<SearchApplicationListItem, String> PARSER = new ConstructingObjectParser<>(
+        "search_application_list_item`",
+        false,
+        (params) -> {
+            final String name = (String) params[0];
+            @SuppressWarnings("unchecked")
+            final String[] indices = ((List<String>) params[1]).toArray(String[]::new);
+            final String analyticsCollectionName = (String) params[2];
+            final Long updatedAtMillis = (Long) params[3];
+            return new SearchApplicationListItem(name, indices, analyticsCollectionName, updatedAtMillis);
+        }
+    );
+
+    static {
+        PARSER.declareStringOrNull(optionalConstructorArg(), NAME_FIELD);
+        PARSER.declareStringArray(constructorArg(), INDICES_FIELD);
+        PARSER.declareStringOrNull(optionalConstructorArg(), ANALYTICS_COLLECTION_NAME_FIELD);
+        PARSER.declareLong(optionalConstructorArg(), UPDATED_AT_MILLIS_FIELD);
+    }
+
+    public SearchApplicationListItem fromXContent(XContentParser parser) {
+        return PARSER.apply(parser, null);
+    }
+
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeString(name);
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/GetAnalyticsCollectionResponseSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/GetAnalyticsCollectionResponseBWCSerializingTests.java
similarity index 70%
rename from x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/GetAnalyticsCollectionResponseSerializingTests.java
rename to x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/GetAnalyticsCollectionResponseBWCSerializingTests.java
index d4433320ddc5c..4ce61b44c0dea 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/GetAnalyticsCollectionResponseSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/GetAnalyticsCollectionResponseBWCSerializingTests.java
@@ -7,14 +7,16 @@
 
 package org.elasticsearch.xpack.application.analytics.action;
 
+import org.elasticsearch.TransportVersion;
 import org.elasticsearch.common.io.stream.Writeable;
-import org.elasticsearch.test.AbstractWireSerializingTestCase;
 import org.elasticsearch.xpack.application.analytics.AnalyticsCollection;
+import org.elasticsearch.xpack.core.ml.AbstractBWCWireSerializationTestCase;
 
 import java.io.IOException;
 import java.util.List;
 
-public class GetAnalyticsCollectionResponseSerializingTests extends AbstractWireSerializingTestCase<GetAnalyticsCollectionAction.Response> {
+public class GetAnalyticsCollectionResponseBWCSerializingTests extends AbstractBWCWireSerializationTestCase<
+    GetAnalyticsCollectionAction.Response> {
 
     @Override
     protected Writeable.Reader<GetAnalyticsCollectionAction.Response> instanceReader() {
@@ -31,4 +33,12 @@ protected GetAnalyticsCollectionAction.Response createTestInstance() {
     protected GetAnalyticsCollectionAction.Response mutateInstance(GetAnalyticsCollectionAction.Response instance) throws IOException {
         return randomValueOtherThan(instance, this::createTestInstance);
     }
+
+    @Override
+    protected GetAnalyticsCollectionAction.Response mutateInstanceForVersion(
+        GetAnalyticsCollectionAction.Response instance,
+        TransportVersion version
+    ) {
+        return instance;
+    }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventDebugResponseSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventDebugResponseBWCSerializingTests.java
similarity index 69%
rename from x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventDebugResponseSerializingTests.java
rename to x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventDebugResponseBWCSerializingTests.java
index 0a7bb6567fe3b..e91c23bac4b66 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventDebugResponseSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventDebugResponseBWCSerializingTests.java
@@ -7,14 +7,16 @@
 
 package org.elasticsearch.xpack.application.analytics.action;
 
+import org.elasticsearch.TransportVersion;
 import org.elasticsearch.common.io.stream.Writeable;
-import org.elasticsearch.test.AbstractWireSerializingTestCase;
+import org.elasticsearch.xpack.core.ml.AbstractBWCWireSerializationTestCase;
 
 import java.io.IOException;
 
 import static org.elasticsearch.xpack.application.analytics.event.AnalyticsEventTestUtils.randomAnalyticsEvent;
 
-public class PostAnalyticsEventDebugResponseSerializingTests extends AbstractWireSerializingTestCase<PostAnalyticsEventAction.Response> {
+public class PostAnalyticsEventDebugResponseBWCSerializingTests extends AbstractBWCWireSerializationTestCase<
+    PostAnalyticsEventAction.Response> {
 
     @Override
     protected Writeable.Reader<PostAnalyticsEventAction.Response> instanceReader() {
@@ -30,4 +32,12 @@ protected PostAnalyticsEventAction.Response createTestInstance() {
     protected PostAnalyticsEventAction.Response mutateInstance(PostAnalyticsEventAction.Response instance) throws IOException {
         return randomValueOtherThan(instance, this::createTestInstance);
     }
+
+    @Override
+    protected PostAnalyticsEventAction.Response mutateInstanceForVersion(
+        PostAnalyticsEventAction.Response instance,
+        TransportVersion version
+    ) {
+        return instance;
+    }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventRequestSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventRequestBWCSerializingTests.java
similarity index 87%
rename from x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventRequestSerializingTests.java
rename to x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventRequestBWCSerializingTests.java
index 567187ff179f0..0fadef93088ff 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventRequestSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventRequestBWCSerializingTests.java
@@ -7,14 +7,15 @@
 
 package org.elasticsearch.xpack.application.analytics.action;
 
+import org.elasticsearch.TransportVersion;
 import org.elasticsearch.common.ValidationException;
 import org.elasticsearch.common.bytes.BytesArray;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.core.Tuple;
-import org.elasticsearch.test.AbstractWireSerializingTestCase;
 import org.elasticsearch.xcontent.XContentType;
 import org.elasticsearch.xpack.application.analytics.event.AnalyticsEvent;
+import org.elasticsearch.xpack.core.ml.AbstractBWCWireSerializationTestCase;
 
 import java.io.IOException;
 import java.util.Collections;
@@ -25,7 +26,7 @@
 import static org.elasticsearch.xpack.application.analytics.event.AnalyticsEventTestUtils.randomInetAddress;
 import static org.mockito.Mockito.mock;
 
-public class PostAnalyticsEventRequestSerializingTests extends AbstractWireSerializingTestCase<PostAnalyticsEventAction.Request> {
+public class PostAnalyticsEventRequestBWCSerializingTests extends AbstractBWCWireSerializationTestCase<PostAnalyticsEventAction.Request> {
 
     public void testValidate() {
         assertNull(createTestInstance().validate());
@@ -83,4 +84,12 @@ protected PostAnalyticsEventAction.Request createTestInstance() {
             new BytesArray(randomByteArrayOfLength(20))
         ).eventTime(randomLong()).debug(randomBoolean()).headers(randomHeaders()).clientAddress(randomInetAddress()).request();
     }
+
+    @Override
+    protected PostAnalyticsEventAction.Request mutateInstanceForVersion(
+        PostAnalyticsEventAction.Request instance,
+        TransportVersion version
+    ) {
+        return instance;
+    }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/rules/action/ListQueryRulesetsActionResponseSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/rules/action/ListQueryRulesetsActionResponseBWCSerializingTests.java
similarity index 75%
rename from x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/rules/action/ListQueryRulesetsActionResponseSerializingTests.java
rename to x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/rules/action/ListQueryRulesetsActionResponseBWCSerializingTests.java
index 65755464f92df..0b3cbdab9a946 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/rules/action/ListQueryRulesetsActionResponseSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/rules/action/ListQueryRulesetsActionResponseBWCSerializingTests.java
@@ -7,13 +7,15 @@
 
 package org.elasticsearch.xpack.application.rules.action;
 
+import org.elasticsearch.TransportVersion;
 import org.elasticsearch.common.io.stream.Writeable;
-import org.elasticsearch.test.AbstractWireSerializingTestCase;
 import org.elasticsearch.xpack.application.rules.QueryRuleset;
 import org.elasticsearch.xpack.application.rules.QueryRulesetListItem;
 import org.elasticsearch.xpack.application.search.SearchApplicationTestUtils;
+import org.elasticsearch.xpack.core.ml.AbstractBWCWireSerializationTestCase;
 
-public class ListQueryRulesetsActionResponseSerializingTests extends AbstractWireSerializingTestCase<ListQueryRulesetsAction.Response> {
+public class ListQueryRulesetsActionResponseBWCSerializingTests extends AbstractBWCWireSerializationTestCase<
+    ListQueryRulesetsAction.Response> {
 
     @Override
     protected Writeable.Reader<ListQueryRulesetsAction.Response> instanceReader() {
@@ -36,4 +38,12 @@ protected ListQueryRulesetsAction.Response mutateInstance(ListQueryRulesetsActio
     protected ListQueryRulesetsAction.Response createTestInstance() {
         return randomQueryRulesetListItem();
     }
+
+    @Override
+    protected ListQueryRulesetsAction.Response mutateInstanceForVersion(
+        ListQueryRulesetsAction.Response instance,
+        TransportVersion version
+    ) {
+        return instance;
+    }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/rules/action/PutQueryRulesetActionResponseSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/rules/action/PutQueryRulesetActionResponseSerializingTests.java
index b35380a70b636..e670610775c93 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/rules/action/PutQueryRulesetActionResponseSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/rules/action/PutQueryRulesetActionResponseSerializingTests.java
@@ -7,13 +7,14 @@
 
 package org.elasticsearch.xpack.application.rules.action;
 
+import org.elasticsearch.TransportVersion;
 import org.elasticsearch.action.DocWriteResponse;
 import org.elasticsearch.common.io.stream.Writeable;
-import org.elasticsearch.test.AbstractWireSerializingTestCase;
+import org.elasticsearch.xpack.core.ml.AbstractBWCWireSerializationTestCase;
 
 import java.io.IOException;
 
-public class PutQueryRulesetActionResponseSerializingTests extends AbstractWireSerializingTestCase<PutQueryRulesetAction.Response> {
+public class PutQueryRulesetActionResponseSerializingTests extends AbstractBWCWireSerializationTestCase<PutQueryRulesetAction.Response> {
 
     @Override
     protected Writeable.Reader<PutQueryRulesetAction.Response> instanceReader() {
@@ -29,4 +30,9 @@ protected PutQueryRulesetAction.Response createTestInstance() {
     protected PutQueryRulesetAction.Response mutateInstance(PutQueryRulesetAction.Response instance) throws IOException {
         return randomValueOtherThan(instance, this::createTestInstance);
     }
+
+    @Override
+    protected PutQueryRulesetAction.Response mutateInstanceForVersion(PutQueryRulesetAction.Response instance, TransportVersion version) {
+        return instance;
+    }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/DeleteSearchApplicationActionRequestBWCSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/DeleteSearchApplicationActionRequestBWCSerializingTests.java
index ce1da6276aedd..0711ce6834f28 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/DeleteSearchApplicationActionRequestBWCSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/DeleteSearchApplicationActionRequestBWCSerializingTests.java
@@ -42,6 +42,6 @@ protected DeleteSearchApplicationAction.Request mutateInstanceForVersion(
         DeleteSearchApplicationAction.Request instance,
         TransportVersion version
     ) {
-        return new DeleteSearchApplicationAction.Request(instance.getName());
+        return instance;
     }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/GetSearchApplicationActionRequestBWCSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/GetSearchApplicationActionRequestBWCSerializingTests.java
index c9d95b696134b..6a6efedade06c 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/GetSearchApplicationActionRequestBWCSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/GetSearchApplicationActionRequestBWCSerializingTests.java
@@ -42,6 +42,6 @@ protected GetSearchApplicationAction.Request mutateInstanceForVersion(
         GetSearchApplicationAction.Request instance,
         TransportVersion version
     ) {
-        return new GetSearchApplicationAction.Request(instance.getName());
+        return instance;
     }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/GetSearchApplicationActionResponseBWCSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/GetSearchApplicationActionResponseBWCSerializingTests.java
index 83e432690574d..bb3e36c95f0ab 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/GetSearchApplicationActionResponseBWCSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/GetSearchApplicationActionResponseBWCSerializingTests.java
@@ -48,6 +48,6 @@ protected GetSearchApplicationAction.Response mutateInstanceForVersion(
         GetSearchApplicationAction.Response instance,
         TransportVersion version
     ) {
-        return new GetSearchApplicationAction.Response(instance.searchApp());
+        return instance;
     }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/ListSearchApplicationActionRequestBWCSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/ListSearchApplicationActionRequestBWCSerializingTests.java
index 0a9cb1e690e46..62678e073a633 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/ListSearchApplicationActionRequestBWCSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/ListSearchApplicationActionRequestBWCSerializingTests.java
@@ -47,6 +47,6 @@ protected ListSearchApplicationAction.Request mutateInstanceForVersion(
         ListSearchApplicationAction.Request instance,
         TransportVersion version
     ) {
-        return new ListSearchApplicationAction.Request(instance.query(), instance.pageParams());
+        return instance;
     }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/ListSearchApplicationActionResponseSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/ListSearchApplicationActionResponseBWCSerializingTests.java
similarity index 77%
rename from x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/ListSearchApplicationActionResponseSerializingTests.java
rename to x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/ListSearchApplicationActionResponseBWCSerializingTests.java
index 1457ae7ee56d2..41eb7fabc096a 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/ListSearchApplicationActionResponseSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/ListSearchApplicationActionResponseBWCSerializingTests.java
@@ -7,13 +7,14 @@
 
 package org.elasticsearch.xpack.application.search.action;
 
+import org.elasticsearch.TransportVersion;
 import org.elasticsearch.common.io.stream.Writeable;
-import org.elasticsearch.test.AbstractWireSerializingTestCase;
 import org.elasticsearch.xpack.application.search.SearchApplication;
 import org.elasticsearch.xpack.application.search.SearchApplicationListItem;
 import org.elasticsearch.xpack.application.search.SearchApplicationTestUtils;
+import org.elasticsearch.xpack.core.ml.AbstractBWCWireSerializationTestCase;
 
-public class ListSearchApplicationActionResponseSerializingTests extends AbstractWireSerializingTestCase<
+public class ListSearchApplicationActionResponseBWCSerializingTests extends AbstractBWCWireSerializationTestCase<
     ListSearchApplicationAction.Response> {
 
     @Override
@@ -37,4 +38,12 @@ protected ListSearchApplicationAction.Response mutateInstance(ListSearchApplicat
     protected ListSearchApplicationAction.Response createTestInstance() {
         return randomSearchApplicationListItem();
     }
+
+    @Override
+    protected ListSearchApplicationAction.Response mutateInstanceForVersion(
+        ListSearchApplicationAction.Response instance,
+        TransportVersion version
+    ) {
+        return instance;
+    }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/PutSearchApplicationActionRequestBWCSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/PutSearchApplicationActionRequestBWCSerializingTests.java
index 6e0f177bd508c..0d79950d2081a 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/PutSearchApplicationActionRequestBWCSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/PutSearchApplicationActionRequestBWCSerializingTests.java
@@ -48,6 +48,6 @@ protected PutSearchApplicationAction.Request mutateInstanceForVersion(
         PutSearchApplicationAction.Request instance,
         TransportVersion version
     ) {
-        return new PutSearchApplicationAction.Request(instance.getSearchApplication(), instance.create());
+        return instance;
     }
 }
diff --git a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/PutSearchApplicationActionResponseSerializingTests.java b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/PutSearchApplicationActionResponseBWCSerializingTests.java
similarity index 70%
rename from x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/PutSearchApplicationActionResponseSerializingTests.java
rename to x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/PutSearchApplicationActionResponseBWCSerializingTests.java
index 66479525d692c..4831f972a231e 100644
--- a/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/PutSearchApplicationActionResponseSerializingTests.java
+++ b/x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/action/PutSearchApplicationActionResponseBWCSerializingTests.java
@@ -7,13 +7,14 @@
 
 package org.elasticsearch.xpack.application.search.action;
 
+import org.elasticsearch.TransportVersion;
 import org.elasticsearch.action.DocWriteResponse;
 import org.elasticsearch.common.io.stream.Writeable;
-import org.elasticsearch.test.AbstractWireSerializingTestCase;
+import org.elasticsearch.xpack.core.ml.AbstractBWCWireSerializationTestCase;
 
 import java.io.IOException;
 
-public class PutSearchApplicationActionResponseSerializingTests extends AbstractWireSerializingTestCase<
+public class PutSearchApplicationActionResponseBWCSerializingTests extends AbstractBWCWireSerializationTestCase<
     PutSearchApplicationAction.Response> {
 
     @Override
@@ -30,4 +31,12 @@ protected PutSearchApplicationAction.Response createTestInstance() {
     protected PutSearchApplicationAction.Response mutateInstance(PutSearchApplicationAction.Response instance) throws IOException {
         return randomValueOtherThan(instance, this::createTestInstance);
     }
+
+    @Override
+    protected PutSearchApplicationAction.Response mutateInstanceForVersion(
+        PutSearchApplicationAction.Response instance,
+        TransportVersion version
+    ) {
+        return instance;
+    }
 }