impl(o11y): introduce gcp.client.version

gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/Composer.java

@@ -69,6 +69,7 @@ public static List<GapicClass> generateServiceClasses(GapicContext context) {
     clazzes.addAll(generateClientSettingsClasses(context));
     clazzes.addAll(generateMockClasses(context, context.services()));
     clazzes.addAll(generateTestClasses(context));
+    clazzes.addAll(generateVersionClasses(context));
     return clazzes;
   }
 
@@ -197,6 +198,15 @@ public static List<GapicClass> generateTestClasses(GapicContext context) {
     return clazzes;
   }
 
+  public static List<GapicClass> generateVersionClasses(GapicContext context) {
+    return context.services().stream()
+        .collect(Collectors.toMap(Service::pakkage, s -> s, (s1, s2) -> s1))
+        .values()
+        .stream()
+        .map(service -> LibraryVersionClassComposer.instance().generate(context, service))
+        .collect(Collectors.toList());
+  }
+
   @VisibleForTesting
   static List<GapicClass> prepareExecutableSamples(List<GapicClass> clazzes) {
     // Include license header, apiShortName, and apiVersion

gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/LibraryVersionClassComposer.java

@@ -0,0 +1,95 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.api.generator.gapic.composer;
+
+import com.google.api.generator.engine.ast.AnnotationNode;
+import com.google.api.generator.engine.ast.AssignmentExpr;
+import com.google.api.generator.engine.ast.ClassDefinition;
+import com.google.api.generator.engine.ast.CommentStatement;
+import com.google.api.generator.engine.ast.ConcreteReference;
+import com.google.api.generator.engine.ast.ExprStatement;
+import com.google.api.generator.engine.ast.LineComment;
+import com.google.api.generator.engine.ast.ScopeNode;
+import com.google.api.generator.engine.ast.StringObjectValue;
+import com.google.api.generator.engine.ast.TypeNode;
+import com.google.api.generator.engine.ast.ValueExpr;
+import com.google.api.generator.engine.ast.Variable;
+import com.google.api.generator.engine.ast.VariableExpr;
+import com.google.api.generator.gapic.model.GapicClass;
+import com.google.api.generator.gapic.model.GapicContext;
+import com.google.api.generator.gapic.model.Service;
+import java.util.Arrays;
+
+public class LibraryVersionClassComposer {
+  private static final LibraryVersionClassComposer INSTANCE = new LibraryVersionClassComposer();
+
+  private LibraryVersionClassComposer() {}
+
+  public static LibraryVersionClassComposer instance() {
+    return INSTANCE;
+  }
+
+  public GapicClass generate(GapicContext context, Service service) {
+    String packageName = service.pakkage() + ".stub";
+    String className = "Version";
+
+    String artifact = context.artifact();
+    String artifactId = artifact;
+    if (artifact != null && artifact.contains(":")) {
+      artifactId = artifact.split(":")[1];
+    }
+
+    VariableExpr versionVarExpr =
+        VariableExpr.withVariable(
+            Variable.builder().setType(TypeNode.STRING).setName("VERSION").build());
+    AssignmentExpr versionAssignmentExpr =
+        AssignmentExpr.builder()
+            .setVariableExpr(
+                versionVarExpr.toBuilder()
+                    .setIsDecl(true)
+                    .setScope(ScopeNode.PUBLIC)
+                    .setIsStatic(true)
+                    .setIsFinal(true)
+                    .build())
+            .setValueExpr(ValueExpr.withValue(StringObjectValue.withValue("0.0.0-SNAPSHOT")))
+            .build();
+
+    ClassDefinition classDef =
+        ClassDefinition.builder()
+            .setPackageString(packageName)
+            .setAnnotations(
+                Arrays.asList(
+                    AnnotationNode.builder()
+                        .setType(
+                            TypeNode.withReference(
+                                ConcreteReference.withClazz(com.google.api.core.InternalApi.class)))
+                        .setDescription("For internal use only")
+                        .build()))
+            .setScope(ScopeNode.LOCAL)
+            .setIsFinal(true)
+            .setName(className)
+            .setStatements(
+                Arrays.asList(
+                    CommentStatement.withComment(
+                        LineComment.withComment(
+                            String.format("{x-version-update-start:%s:current}", artifactId))),
+                    ExprStatement.withExpr(versionAssignmentExpr),
+                    CommentStatement.withComment(
+                        LineComment.withComment("{x-version-update-end}"))))
+            .build();
+
+    return GapicClass.create(GapicClass.Kind.MAIN, classDef);
+  }
+}

gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/common/AbstractServiceStubSettingsClassComposer.java

@@ -1063,7 +1063,7 @@ private List<MethodDefinition> createClassMethods(
             SettingsCommentComposer.NEW_BUILDER_METHOD_COMMENT));
     javaMethods.addAll(createBuilderHelperMethods(service, typeStore));
     javaMethods.add(createClassConstructor(service, methodSettingsMemberVarExprs, typeStore));
-    javaMethods.add(createGetLibraryMetadataMethod(context));
+    javaMethods.add(createGetLibraryMetadataMethod(context, service));
     return javaMethods;
   }
 
@@ -2107,7 +2107,7 @@ private static MethodDefinition createNestedClassBuildMethod(
         .build();
   }
 
-  private MethodDefinition createGetLibraryMetadataMethod(GapicContext context) {
+  private MethodDefinition createGetLibraryMetadataMethod(GapicContext context, Service service) {
     TypeNode returnType = FIXED_TYPESTORE.get("LibraryMetadata");
     MethodInvocationExpr libraryMetadataBuilderExpr =
         MethodInvocationExpr.builder()
@@ -2133,6 +2133,23 @@ private MethodDefinition createGetLibraryMetadataMethod(GapicContext context) {
               .build();
     }
 
+    libraryMetadataBuilderExpr =
+        MethodInvocationExpr.builder()
+            .setExprReferenceExpr(libraryMetadataBuilderExpr)
+            .setMethodName("setVersion")
+            .setArguments(
+                VariableExpr.builder()
+                    .setStaticReferenceType(
+                        TypeNode.withReference(
+                            VaporReference.builder()
+                                .setName("Version")
+                                .setPakkage(String.format("%s.stub", service.pakkage()))
+                                .build()))
+                    .setVariable(
+                        Variable.builder().setName("VERSION").setType(TypeNode.STRING).build())
+                    .build())
+            .build();
+
     Expr returnExpr =
         MethodInvocationExpr.builder()
             .setExprReferenceExpr(libraryMetadataBuilderExpr)

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/LibraryVersionClassComposerTest.java

@@ -0,0 +1,34 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.api.generator.gapic.composer;
+
+import com.google.api.generator.gapic.model.GapicClass;
+import com.google.api.generator.gapic.model.GapicContext;
+import com.google.api.generator.gapic.model.Service;
+import com.google.api.generator.test.framework.Assert;
+import com.google.api.generator.test.protoloader.GrpcTestProtoLoader;
+import org.junit.Test;
+
+public class LibraryVersionClassComposerTest {
+
+  @Test
+  public void generateVersionClasses() {
+    GapicContext context = GrpcTestProtoLoader.instance().parseShowcaseEcho();
+    Service service = context.services().get(0);
+    GapicClass clazz = LibraryVersionClassComposer.instance().generate(context, service);
+
+    Assert.assertGoldenClass(this.getClass(), clazz, "EchoVersion.golden");
+  }
+}

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/goldens/EchoVersion.golden

@@ -0,0 +1,11 @@
+package com.google.showcase.v1beta1.stub;
+
+import com.google.api.core.InternalApi;
+
+@InternalApi("For internal use only")
+final class Version {
+  // {x-version-update-start:gapic-showcase:current}
+  public static final String VERSION = "0.0.0-SNAPSHOT";
+  // {x-version-update-end}
+
+}

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/grpc/goldens/ApiVersionTestingStubSettings.golden

@@ -170,7 +170,7 @@ public class EchoWithVersionStubSettings extends StubSettings<EchoWithVersionStu
 
   @Override
   protected LibraryMetadata getLibraryMetadata() {
-    return LibraryMetadata.newBuilder().build();
+    return LibraryMetadata.newBuilder().setVersion(Version.VERSION).build();
   }
 
   /** Builder for EchoWithVersionStubSettings. */

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/grpc/goldens/DeprecatedServiceStubSettings.golden

@@ -187,7 +187,7 @@ public class DeprecatedServiceStubSettings extends StubSettings<DeprecatedServic
 
   @Override
   protected LibraryMetadata getLibraryMetadata() {
-    return LibraryMetadata.newBuilder().build();
+    return LibraryMetadata.newBuilder().setVersion(Version.VERSION).build();
   }
 
   /** Builder for DeprecatedServiceStubSettings. */

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/grpc/goldens/EchoServiceSelectiveGapicStubSettings.golden

@@ -224,7 +224,7 @@ public class EchoServiceShouldGeneratePartialUsualStubSettings
 
   @Override
   protected LibraryMetadata getLibraryMetadata() {
-    return LibraryMetadata.newBuilder().build();
+    return LibraryMetadata.newBuilder().setVersion(Version.VERSION).build();
   }
 
   /** Builder for EchoServiceShouldGeneratePartialUsualStubSettings. */

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/grpc/goldens/EchoStubSettings.golden

@@ -413,6 +413,7 @@ public class EchoStubSettings extends StubSettings<EchoStubSettings> {
     return LibraryMetadata.newBuilder()
         .setArtifactName("com.google.cloud:gapic-showcase")
         .setRepository("googleapis/sdk-platform-java")
+        .setVersion(Version.VERSION)
         .build();
   }
 

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/grpc/goldens/JobServiceStubSettings.golden

@@ -260,7 +260,7 @@ public class JobServiceStubSettings extends StubSettings<JobServiceStubSettings>
 
   @Override
   protected LibraryMetadata getLibraryMetadata() {
-    return LibraryMetadata.newBuilder().build();
+    return LibraryMetadata.newBuilder().setVersion(Version.VERSION).build();
   }
 
   /** Builder for JobServiceStubSettings. */

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/grpc/goldens/LoggingServiceV2StubSettings.golden

@@ -512,7 +512,10 @@ public class LoggingServiceV2StubSettings extends StubSettings<LoggingServiceV2S
 
   @Override
   protected LibraryMetadata getLibraryMetadata() {
-    return LibraryMetadata.newBuilder().build();
+    return LibraryMetadata.newBuilder()
+        .setArtifactName("com.google.cloud:google-cloud-logging")
+        .setVersion(Version.VERSION)
+        .build();
   }
 
   /** Builder for LoggingServiceV2StubSettings. */

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/grpc/goldens/PublisherStubSettings.golden

@@ -522,7 +522,7 @@ public class PublisherStubSettings extends StubSettings<PublisherStubSettings> {
 
   @Override
   protected LibraryMetadata getLibraryMetadata() {
-    return LibraryMetadata.newBuilder().build();
+    return LibraryMetadata.newBuilder().setVersion(Version.VERSION).build();
   }
 
   /** Builder for PublisherStubSettings. */

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/grpcrest/goldens/EchoStubSettings.golden

@@ -445,6 +445,7 @@ public class EchoStubSettings extends StubSettings<EchoStubSettings> {
     return LibraryMetadata.newBuilder()
         .setArtifactName("com.google.cloud:gapic-showcase")
         .setRepository("googleapis/sdk-platform-java")
+        .setVersion(Version.VERSION)
         .build();
   }
 

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/grpcrest/goldens/WickedStubSettings.golden

@@ -192,6 +192,7 @@ public class WickedStubSettings extends StubSettings<WickedStubSettings> {
     return LibraryMetadata.newBuilder()
         .setArtifactName("com.google.cloud:gapic-showcase")
         .setRepository("googleapis/sdk-platform-java")
+        .setVersion(Version.VERSION)
         .build();
   }
 

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/rest/goldens/ComplianceStubSettings.golden

@@ -225,7 +225,7 @@ public class ComplianceStubSettings extends StubSettings<ComplianceStubSettings>
 
   @Override
   protected LibraryMetadata getLibraryMetadata() {
-    return LibraryMetadata.newBuilder().build();
+    return LibraryMetadata.newBuilder().setVersion(Version.VERSION).build();
   }
 
   /** Builder for ComplianceStubSettings. */

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/rest/goldens/HttpJsonApiVersionTestingStubSettings.golden

@@ -172,7 +172,7 @@ public class EchoWithVersionStubSettings extends StubSettings<EchoWithVersionStu
 
   @Override
   protected LibraryMetadata getLibraryMetadata() {
-    return LibraryMetadata.newBuilder().build();
+    return LibraryMetadata.newBuilder().setVersion(Version.VERSION).build();
   }
 
   /** Builder for EchoWithVersionStubSettings. */

gapic-generator-java/src/test/java/com/google/api/generator/test/protoloader/TestProtoLoader.java

@@ -74,6 +74,7 @@ public class TestProtoLoader {
           + " to have the values echoed in the response trailers.";
   private static final String ECHO_SERVICE_REPOSITORY = "googleapis/sdk-platform-java";
   private static final String ECHO_SERVICE_ARTIFACT = "com.google.cloud:gapic-showcase";
+  private static final String LOGGING_SERVICE_ARTIFACT = "com.google.cloud:google-cloud-logging";
   private final String testFilesDirectory;
   private final Transport transport;
 
@@ -505,6 +506,7 @@ public GapicContext parseLogging() {
         .setServiceConfig(config)
         .setHelperResourceNames(outputResourceNames)
         .setTransport(transport)
+        .setArtifact(LOGGING_SERVICE_ARTIFACT)
         .build();
   }
 

gax-java/gax/src/main/java/com/google/api/gax/rpc/LibraryMetadata.java

@@ -65,6 +65,13 @@ public abstract class LibraryMetadata {
   @Nullable
   public abstract String artifactName();
 
+  /**
+   * Returns the version of the client library.
+   *
+   * <p>Example: {@code "2.74.1"}. This maps to the {@code gcp.client.version} attribute.
+   *
+   * @return the version, or {@code null} if not set
+   */
   @Nullable
   public abstract String version();
 
@@ -73,7 +80,7 @@ public static LibraryMetadata empty() {
   }
 
   public boolean isEmpty() {
-    return repository() == null && artifactName() == null;
+    return repository() == null && artifactName() == null && version() == null;
   }
 
   public static LibraryMetadata.Builder newBuilder() {
@@ -86,7 +93,7 @@ public abstract static class Builder {
 
     public abstract Builder setArtifactName(@Nullable String artifactName);
 
-    public abstract Builder setVersion(@Nullable String version);
+    public abstract Builder setVersion(@Nullable String libraryVersion);
 
     public abstract LibraryMetadata build();
   }

gax-java/gax/src/main/java/com/google/api/gax/tracing/ApiTracerContext.java

@@ -167,7 +167,7 @@
   /**
    * @return a map of attributes to be included in attempt-level spans
    */
   public Map<String, Object> getAttemptAttributes() {
     Map<String, Object> attributes = new HashMap<>();
     if (!Strings.isNullOrEmpty(serverAddress())) {
       attributes.put(ObservabilityAttributes.SERVER_ADDRESS_ATTRIBUTE, serverAddress());
@@ -186,6 +186,9 @@
         attributes.put(
             ObservabilityAttributes.ARTIFACT_ATTRIBUTE, libraryMetadata().artifactName());
       }
+      if (!Strings.isNullOrEmpty(libraryMetadata().version())) {
+        attributes.put(ObservabilityAttributes.VERSION_ATTRIBUTE, libraryMetadata().version());
+      }
     }
     if (transport() == Transport.GRPC && !Strings.isNullOrEmpty(fullMethodName())) {
       attributes.put(ObservabilityAttributes.GRPC_RPC_METHOD_ATTRIBUTE, fullMethodName());

gax-java/gax/src/main/java/com/google/api/gax/tracing/ObservabilityAttributes.java

@@ -53,6 +53,9 @@ public class ObservabilityAttributes {
   /** The artifact name of the client library (e.g., "google-cloud-vision"). */
   public static final String ARTIFACT_ATTRIBUTE = "gcp.client.artifact";
 
+  /** The version of the client library (e.g., "1.2.3"). */
+  public static final String VERSION_ATTRIBUTE = "gcp.client.version";
+
   /** The full RPC method name, including package, service, and method. */
   public static final String GRPC_RPC_METHOD_ATTRIBUTE = "rpc.method";