elastic · rjernst · Oct 6, 2025 · Oct 6, 2025
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/protocol/xpack/XPackInfoRequest.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/protocol/xpack/XPackInfoRequest.java
@@ -6,13 +6,10 @@
  */
 package org.elasticsearch.protocol.xpack;
 
-import org.elasticsearch.TransportVersion;
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.LegacyActionRequest;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
-import org.elasticsearch.license.License;
 
 import java.io.IOException;
 import java.util.EnumSet;
@@ -58,9 +55,6 @@ public XPackInfoRequest(StreamInput in) throws IOException {
             categories.add(Category.valueOf(in.readString()));
         }
         this.categories = categories;
-        if (hasLicenseVersionField(in.getTransportVersion())) {
-            int ignoredLicenseVersion = in.readVInt();
-        }
     }
 
     public void setVerbose(boolean verbose) {
@@ -92,12 +86,5 @@ public void writeTo(StreamOutput out) throws IOException {
         for (Category category : categories) {
             out.writeString(category.name());
         }
-        if (hasLicenseVersionField(out.getTransportVersion())) {
-            out.writeVInt(License.VERSION_CURRENT);
-        }
-    }
-
-    private static boolean hasLicenseVersionField(TransportVersion streamVersion) {
-        return streamVersion.between(TransportVersions.V_7_8_1, TransportVersions.V_8_0_0);
     }
 }
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/protocol/xpack/XPackInfoResponse.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/protocol/xpack/XPackInfoResponse.java
@@ -6,7 +6,6 @@
  */
 package org.elasticsearch.protocol.xpack;
 
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
@@ -328,19 +327,13 @@ public FeatureSet(String name, boolean available, boolean enabled) {
 
             public FeatureSet(StreamInput in) throws IOException {
                 this(in.readString(), in.readBoolean(), in.readBoolean());
-                if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
-                    in.readGenericMap(); // backcompat reading native code info, but no longer used here
-                }
             }
 
             @Override
             public void writeTo(StreamOutput out) throws IOException {
                 out.writeString(name);
                 out.writeBoolean(available);
                 out.writeBoolean(enabled);
-                if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
-                    out.writeGenericMap(Collections.emptyMap());
-                }
             }
 
             public String name() {

diff --git a/...plugin/core/src/main/java/org/elasticsearch/protocol/xpack/graph/GraphExploreRequest.java b/...plugin/core/src/main/java/org/elasticsearch/protocol/xpack/graph/GraphExploreRequest.java
@@ -6,7 +6,6 @@
  */
 package org.elasticsearch.protocol.xpack.graph;
 
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.IndicesRequest;
 import org.elasticsearch.action.LegacyActionRequest;
@@ -111,10 +110,6 @@ public GraphExploreRequest(StreamInput in) throws IOException {
 
         indices = in.readStringArray();
         indicesOptions = IndicesOptions.readIndicesOptions(in);
-        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
-            String[] types = in.readStringArray();
-            assert types.length == 0;
-        }
         routing = in.readOptionalString();
         timeout = in.readOptionalTimeValue();
         sampleSize = in.readInt();
@@ -174,9 +169,6 @@ public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
         out.writeStringArray(indices);
         indicesOptions.writeIndicesOptions(out);
-        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
-            out.writeStringArray(Strings.EMPTY_ARRAY);
-        }
         out.writeOptionalString(routing);
         out.writeOptionalTimeValue(timeout);
 

diff --git a/...k/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/ExplainLifecycleRequest.java b/...k/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/ExplainLifecycleRequest.java
@@ -7,7 +7,6 @@
 
 package org.elasticsearch.xpack.core.ilm;
 
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.IndicesRequest;
 import org.elasticsearch.action.support.IndicesOptions;
@@ -51,9 +50,6 @@ public ExplainLifecycleRequest(TimeValue masterTimeout) {
     public ExplainLifecycleRequest(StreamInput in) throws IOException {
         super(in);
         indices = in.readStringArray();
-        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
-            in.readStringArray();
-        }
         indicesOptions = IndicesOptions.readIndicesOptions(in);
         onlyErrors = in.readBoolean();
         onlyManaged = in.readBoolean();

diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/MlMetadata.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/MlMetadata.java
@@ -7,10 +7,8 @@
 package org.elasticsearch.xpack.core.ml;
 
 import org.elasticsearch.TransportVersion;
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.Diff;
-import org.elasticsearch.cluster.DiffableUtils;
 import org.elasticsearch.cluster.NamedDiff;
 import org.elasticsearch.cluster.SimpleDiffable;
 import org.elasticsearch.cluster.metadata.Metadata;
@@ -28,12 +26,10 @@
 import org.elasticsearch.xpack.core.ml.job.config.Job;
 
 import java.io.IOException;
-import java.util.Collections;
 import java.util.EnumSet;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Objects;
-import java.util.SortedMap;
 
 public class MlMetadata implements Metadata.ProjectCustom {
 
@@ -87,28 +83,12 @@ public Diff<Metadata.ProjectCustom> diff(Metadata.ProjectCustom previousState) {
     }
 
     public MlMetadata(StreamInput in) throws IOException {
-        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
-            int size = in.readVInt();
-            for (int i = 0; i < size; i++) {
-                in.readString();
-                new Job(in);
-            }
-            size = in.readVInt();
-            for (int i = 0; i < size; i++) {
-                in.readString();
-                new DatafeedConfig(in);
-            }
-        }
         this.upgradeMode = in.readBoolean();
         this.resetMode = in.readBoolean();
     }
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
-        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
-            writeMap(Collections.emptySortedMap(), out);
-            writeMap(Collections.emptySortedMap(), out);
-        }
         out.writeBoolean(upgradeMode);
         out.writeBoolean(resetMode);
     }
@@ -140,15 +120,6 @@ public static class MlMetadataDiff implements NamedDiff<Metadata.ProjectCustom>
         }
 
         public MlMetadataDiff(StreamInput in) throws IOException {
-            if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
-                DiffableUtils.readJdkMapDiff(in, DiffableUtils.getStringKeySerializer(), Job::new, MlMetadataDiff::readJobDiffFrom);
-                DiffableUtils.readJdkMapDiff(
-                    in,
-                    DiffableUtils.getStringKeySerializer(),
-                    DatafeedConfig::new,
-                    MlMetadataDiff::readDatafeedDiffFrom
-                );
-            }
             upgradeMode = in.readBoolean();
             resetMode = in.readBoolean();
         }
@@ -165,12 +136,6 @@ public Metadata.ProjectCustom apply(Metadata.ProjectCustom part) {
 
         @Override
         public void writeTo(StreamOutput out) throws IOException {
-            if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
-                SortedMap<String, Job> jobs = Collections.emptySortedMap();
-                DiffableUtils.diff(jobs, jobs, DiffableUtils.getStringKeySerializer()).writeTo(out);
-                SortedMap<String, DatafeedConfig> datafeeds = Collections.emptySortedMap();
-                DiffableUtils.diff(datafeeds, datafeeds, DiffableUtils.getStringKeySerializer()).writeTo(out);
-            }
             out.writeBoolean(upgradeMode);
             out.writeBoolean(resetMode);
         }

diff --git a/...ore/src/main/java/org/elasticsearch/xpack/core/ml/action/GetTrainedModelsStatsAction.java b/...ore/src/main/java/org/elasticsearch/xpack/core/ml/action/GetTrainedModelsStatsAction.java
@@ -7,7 +7,6 @@
 package org.elasticsearch.xpack.core.ml.action;
 
 import org.elasticsearch.ElasticsearchException;
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionType;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -110,19 +109,11 @@ public TrainedModelStats(
 
             public TrainedModelStats(StreamInput in) throws IOException {
                 modelId = in.readString();
-                if (in.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
-                    modelSizeStats = in.readOptionalWriteable(TrainedModelSizeStats::new);
-                } else {
-                    modelSizeStats = null;
-                }
+                modelSizeStats = in.readOptionalWriteable(TrainedModelSizeStats::new);
                 ingestStats = IngestStats.read(in);
                 pipelineCount = in.readVInt();
                 inferenceStats = in.readOptionalWriteable(InferenceStats::new);
-                if (in.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
-                    this.deploymentStats = in.readOptionalWriteable(AssignmentStats::new);
-                } else {
-                    this.deploymentStats = null;
-                }
+                this.deploymentStats = in.readOptionalWriteable(AssignmentStats::new);
             }
 
             public String getModelId() {
@@ -174,15 +165,11 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
             @Override
             public void writeTo(StreamOutput out) throws IOException {
                 out.writeString(modelId);
-                if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
-                    out.writeOptionalWriteable(modelSizeStats);
-                }
+                out.writeOptionalWriteable(modelSizeStats);
                 ingestStats.writeTo(out);
                 out.writeVInt(pipelineCount);
                 out.writeOptionalWriteable(inferenceStats);
-                if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
-                    out.writeOptionalWriteable(deploymentStats);
-                }
+                out.writeOptionalWriteable(deploymentStats);
             }
 
             @Override

diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/datafeed/AggProvider.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/datafeed/AggProvider.java
@@ -8,7 +8,6 @@
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -117,7 +116,7 @@ static AggProvider fromStream(StreamInput in) throws IOException {
             in.readGenericMap(),
             in.readOptionalWriteable(AggregatorFactories.Builder::new),
             in.readException(),
-            in.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0) ? in.readBoolean() : false
+            in.readBoolean()
         );
     }
 
@@ -140,9 +139,7 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeGenericMap(aggs);
         out.writeOptionalWriteable(parsedAggs);
         out.writeException(parsingException);
-        if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
-            out.writeBoolean(rewroteAggs);
-        }
+        out.writeBoolean(rewroteAggs);
     }
 
     public Exception getParsingException() {

diff --git a/...ugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/TrainedModelConfig.java b/...ugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/TrainedModelConfig.java
@@ -104,7 +104,6 @@ public class TrainedModelConfig implements ToXContentObject, Writeable {
     public static final ParseField PER_ALLOCATION_MEMORY_BYTES = new ParseField("per_allocation_memory_bytes");
     public static final ParseField PLATFORM_ARCHITECTURE = new ParseField("platform_architecture");
 
-    public static final TransportVersion VERSION_3RD_PARTY_CONFIG_ADDED = TransportVersions.V_8_0_0;
     public static final TransportVersion VERSION_ALLOCATION_MEMORY_ADDED = TransportVersions.V_8_11_X;
 
     // These parsers follow the pattern that metadata is parsed leniently (to allow for enhancements), whilst config is parsed strictly
@@ -278,13 +277,8 @@ public TrainedModelConfig(StreamInput in) throws IOException {
         this.defaultFieldMap = in.readBoolean() ? in.readImmutableMap(StreamInput::readString) : null;
 
         this.inferenceConfig = in.readOptionalNamedWriteable(InferenceConfig.class);
-        if (in.getTransportVersion().onOrAfter(VERSION_3RD_PARTY_CONFIG_ADDED)) {
-            this.modelType = in.readOptionalEnum(TrainedModelType.class);
-            this.location = in.readOptionalNamedWriteable(TrainedModelLocation.class);
-        } else {
-            this.modelType = null;
-            this.location = null;
-        }
+        this.modelType = in.readOptionalEnum(TrainedModelType.class);
+        this.location = in.readOptionalNamedWriteable(TrainedModelLocation.class);
         if (in.getTransportVersion().onOrAfter(TransportVersions.V_8_8_0)) {
             modelPackageConfig = in.readOptionalWriteable(ModelPackageConfig::new);
             fullDefinition = in.readOptionalBoolean();
@@ -471,10 +465,8 @@ public void writeTo(StreamOutput out) throws IOException {
             out.writeBoolean(false);
         }
         out.writeOptionalNamedWriteable(inferenceConfig);
-        if (out.getTransportVersion().onOrAfter(VERSION_3RD_PARTY_CONFIG_ADDED)) {
-            out.writeOptionalEnum(modelType);
-            out.writeOptionalNamedWriteable(location);
-        }
+        out.writeOptionalEnum(modelType);
+        out.writeOptionalNamedWriteable(location);
 
         if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_8_0)) {
             out.writeOptionalWriteable(modelPackageConfig);
@@ -1094,11 +1086,7 @@ public static LazyModelDefinition fromBase64String(String base64String) {
         }
 
         public static LazyModelDefinition fromStreamInput(StreamInput input) throws IOException {
-            if (input.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
-                return new LazyModelDefinition(input.readBytesReference(), null);
-            } else {
-                return fromBase64String(input.readString());
-            }
+            return new LazyModelDefinition(input.readBytesReference(), null);
         }
 
         private LazyModelDefinition(LazyModelDefinition definition) {
@@ -1158,11 +1146,7 @@ private void ensureParsedDefinitionUnsafe(NamedXContentRegistry xContentRegistry
 
         @Override
         public void writeTo(StreamOutput out) throws IOException {
-            if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
-                out.writeBytesReference(getCompressedDefinition());
-            } else {
-                out.writeString(getBase64CompressedDefinition());
-            }
+            out.writeBytesReference(getCompressedDefinition());
         }
 
         @Override

diff --git a/.../org/elasticsearch/xpack/core/ml/inference/assignment/TrainedModelAssignmentMetadata.java b/.../org/elasticsearch/xpack/core/ml/inference/assignment/TrainedModelAssignmentMetadata.java
@@ -10,7 +10,6 @@
 import org.elasticsearch.ResourceAlreadyExistsException;
 import org.elasticsearch.ResourceNotFoundException;
 import org.elasticsearch.TransportVersion;
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.Diff;
 import org.elasticsearch.cluster.DiffableUtils;
@@ -156,7 +155,7 @@ public String getWriteableName() {
 
     @Override
     public TransportVersion getMinimalSupportedVersion() {
-        return TransportVersions.V_8_0_0;
+        return TransportVersion.minimumCompatible();
     }
 
     @Override
@@ -321,7 +320,7 @@ public String getWriteableName() {
 
         @Override
         public TransportVersion getMinimalSupportedVersion() {
-            return TransportVersions.V_8_0_0;
+            return TransportVersion.minimumCompatible();
         }
 
         @Override

diff --git a/.../src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/FillMaskConfig.java b/.../src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/FillMaskConfig.java
@@ -8,7 +8,6 @@
 package org.elasticsearch.xpack.core.ml.inference.trainedmodel;
 
 import org.elasticsearch.TransportVersion;
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -162,7 +161,7 @@ public MlConfigVersion getMinimalSupportedMlConfigVersion() {
 
     @Override
     public TransportVersion getMinimalSupportedTransportVersion() {
-        return TransportVersions.V_8_0_0;
+        return TransportVersion.minimumCompatible();
     }
 
     @Override

diff --git a/...ain/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/FillMaskConfigUpdate.java b/...ain/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/FillMaskConfigUpdate.java
@@ -8,7 +8,6 @@
 package org.elasticsearch.xpack.core.ml.inference.trainedmodel;
 
 import org.elasticsearch.TransportVersion;
-import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.xcontent.ObjectParser;
@@ -105,7 +104,7 @@ public String getName() {
 
     @Override
     public TransportVersion getMinimalSupportedVersion() {
-        return TransportVersions.V_8_0_0;
+        return TransportVersion.minimumCompatible();
     }
 
     @Override