diff --git a/gapic-generator-java/src/main/java/com/google/api/generator/engine/ast/TryCatchStatement.java b/gapic-generator-java/src/main/java/com/google/api/generator/engine/ast/TryCatchStatement.java
index 0cc76f3eea..61efac914a 100644
--- a/gapic-generator-java/src/main/java/com/google/api/generator/engine/ast/TryCatchStatement.java
+++ b/gapic-generator-java/src/main/java/com/google/api/generator/engine/ast/TryCatchStatement.java
@@ -20,7 +20,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 @AutoValue
@@ -60,7 +60,7 @@ public abstract static class Builder {
 
     public abstract Builder setIsSampleCode(boolean isSampleCode);
 
-    public Builder addCatch(@Nonnull VariableExpr variableExpr, List<Statement> body) {
+    public Builder addCatch(@NonNull VariableExpr variableExpr, List<Statement> body) {
       List<VariableExpr> catchVarExprs = new ArrayList<>(catchVariableExprs());
       catchVarExprs.add(variableExpr);
       setCatchVariableExprs(catchVarExprs);
diff --git a/gapic-generator-java/src/main/java/com/google/api/generator/engine/writer/ImportWriterVisitor.java b/gapic-generator-java/src/main/java/com/google/api/generator/engine/writer/ImportWriterVisitor.java
index d6e6a0320c..3552a97e4f 100644
--- a/gapic-generator-java/src/main/java/com/google/api/generator/engine/writer/ImportWriterVisitor.java
+++ b/gapic-generator-java/src/main/java/com/google/api/generator/engine/writer/ImportWriterVisitor.java
@@ -69,7 +69,7 @@
 import java.util.Set;
 import java.util.TreeSet;
 import java.util.stream.Collectors;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 public class ImportWriterVisitor implements AstNodeVisitor {
@@ -91,12 +91,12 @@ public void clear() {
     importShortNames.clear();
   }
 
-  public void initialize(@Nonnull String currentPackage) {
+  public void initialize(@NonNull String currentPackage) {
     this.currentPackage = currentPackage;
     currentClassName = null;
   }
 
-  public void initialize(@Nonnull String currentPackage, @Nonnull String currentClassName) {
+  public void initialize(@NonNull String currentPackage, @NonNull String currentClassName) {
     this.currentPackage = currentPackage;
     this.currentClassName = currentClassName;
   }
diff --git a/gapic-generator-java/src/main/java/com/google/api/generator/gapic/model/SourceCodeInfoLocation.java b/gapic-generator-java/src/main/java/com/google/api/generator/gapic/model/SourceCodeInfoLocation.java
index f39cb39530..da7cac2f59 100644
--- a/gapic-generator-java/src/main/java/com/google/api/generator/gapic/model/SourceCodeInfoLocation.java
+++ b/gapic-generator-java/src/main/java/com/google/api/generator/gapic/model/SourceCodeInfoLocation.java
@@ -15,20 +15,20 @@
 package com.google.api.generator.gapic.model;
 
 import com.google.protobuf.DescriptorProtos.SourceCodeInfo.Location;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * A light wrapper around SourceCodeInfo.Location to provide cleaner protobuf comments. Please see
  * additional documentation on descriptor.proto.
  */
 public class SourceCodeInfoLocation {
-  @Nonnull private final Location location;
+  @NonNull private final Location location;
 
   private SourceCodeInfoLocation(Location location) {
     this.location = location;
   }
 
-  public static SourceCodeInfoLocation create(@Nonnull Location location) {
+  public static SourceCodeInfoLocation create(@NonNull Location location) {
     return new SourceCodeInfoLocation(location);
   }
 
diff --git a/gapic-generator-java/src/main/java/com/google/api/generator/gapic/protoparser/TypeParser.java b/gapic-generator-java/src/main/java/com/google/api/generator/gapic/protoparser/TypeParser.java
index 49b17d25db..ea33250203 100644
--- a/gapic-generator-java/src/main/java/com/google/api/generator/gapic/protoparser/TypeParser.java
+++ b/gapic-generator-java/src/main/java/com/google/api/generator/gapic/protoparser/TypeParser.java
@@ -34,7 +34,7 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 public class TypeParser {
   private static Reference REFERENCE_BYTE_STRING = ConcreteReference.withClazz(ByteString.class);
@@ -62,7 +62,7 @@ public class TypeParser {
           .put(JavaType.BYTE_STRING, REFERENCE_BYTE_STRING)
           .build();
 
-  public static TypeNode parseType(@Nonnull FieldDescriptor field) {
+  public static TypeNode parseType(@NonNull FieldDescriptor field) {
     if (field.isMapField()) {
       return createMapType(field);
     }
@@ -83,11 +83,11 @@ public static TypeNode parseType(@Nonnull FieldDescriptor field) {
     return TypeNode.withReference(parseFieldReference(field));
   }
 
-  public static TypeNode parseType(@Nonnull Descriptor messageDescriptor) {
+  public static TypeNode parseType(@NonNull Descriptor messageDescriptor) {
     return TypeNode.withReference(parseMessageReference(messageDescriptor));
   }
 
-  public static TypeNode parseType(@Nonnull EnumDescriptor enumDescriptor) {
+  public static TypeNode parseType(@NonNull EnumDescriptor enumDescriptor) {
     return TypeNode.withReference(parseEnumReference(enumDescriptor));
   }
 
@@ -119,7 +119,7 @@ static Reference parseFieldReference(FieldDescriptor field) {
   }
 
   @VisibleForTesting
-  static Reference parseMessageReference(@Nonnull Descriptor messageDescriptor) {
+  static Reference parseMessageReference(@NonNull Descriptor messageDescriptor) {
     List<String> outerNestedTypeNames = new ArrayList<>();
     FileOptions fileOptions = messageDescriptor.getFile().getOptions();
     String javaOuterClassname =
@@ -179,7 +179,7 @@ static Reference parseMessageReference(@Nonnull Descriptor messageDescriptor) {
   }
 
   @VisibleForTesting
-  static Reference parseEnumReference(@Nonnull EnumDescriptor enumDescriptor) {
+  static Reference parseEnumReference(@NonNull EnumDescriptor enumDescriptor) {
     // This is similar to parseMessageReference, but we make it a separate method because
     // EnumDescriptor and Descriptor are sibling types.
     FileOptions fileOptions = enumDescriptor.getFile().getOptions();
diff --git a/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/GrpcCallContext.java b/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/GrpcCallContext.java
index 246c76405b..ee898af17e 100644
--- a/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/GrpcCallContext.java
+++ b/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/GrpcCallContext.java
@@ -64,7 +64,7 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -626,7 +626,7 @@ public GrpcCallContext withRequestParamsDynamicHeaderOption(String requestParams
 
   /** {@inheritDoc} */
   @Override
-  @Nonnull
+  @NonNull
   public ApiTracer getTracer() {
     ApiTracer tracer = callOptions.getOption(TRACER_KEY);
     if (tracer == null) {
@@ -637,7 +637,7 @@ public ApiTracer getTracer() {
 
   /** {@inheritDoc} */
   @Override
-  public GrpcCallContext withTracer(@Nonnull ApiTracer tracer) {
+  public GrpcCallContext withTracer(@NonNull ApiTracer tracer) {
     Preconditions.checkNotNull(tracer);
     return withCallOptions(callOptions.withOption(TRACER_KEY, tracer));
   }
diff --git a/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/GrpcCallableFactory.java b/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/GrpcCallableFactory.java
index 974feb0c43..3d703ea701 100644
--- a/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/GrpcCallableFactory.java
+++ b/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/GrpcCallableFactory.java
@@ -61,7 +61,7 @@
 import io.grpc.MethodDescriptor;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /** Class with utility methods to create grpc-based direct callables. */
 public class GrpcCallableFactory {
@@ -329,7 +329,7 @@ ClientStreamingCallable<RequestT, ResponseT> createClientStreamingCallable(
   }
 
   @InternalApi("Visible for testing")
-  static SpanName getSpanName(@Nonnull MethodDescriptor<?, ?> methodDescriptor) {
+  static SpanName getSpanName(@NonNull MethodDescriptor<?, ?> methodDescriptor) {
     Matcher matcher = FULL_METHOD_NAME_REGEX.matcher(methodDescriptor.getFullMethodName());
 
     Preconditions.checkArgument(matcher.matches(), "Invalid fullMethodName");
diff --git a/gax-java/gax-grpc/src/test/java/com/google/api/gax/grpc/GrpcDirectStreamControllerTest.java b/gax-java/gax-grpc/src/test/java/com/google/api/gax/grpc/GrpcDirectStreamControllerTest.java
index 5f7bdf8819..6c8d6e5a04 100644
--- a/gax-java/gax-grpc/src/test/java/com/google/api/gax/grpc/GrpcDirectStreamControllerTest.java
+++ b/gax-java/gax-grpc/src/test/java/com/google/api/gax/grpc/GrpcDirectStreamControllerTest.java
@@ -52,7 +52,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.Timeout;
@@ -68,13 +68,13 @@ void testRetryNoRaceCondition() throws Exception {
         ManagedChannelBuilder.forAddress("localhost", 1234).usePlaintext().build();
     StreamResumptionStrategy<Color, Money> resumptionStrategy =
         new StreamResumptionStrategy<Color, Money>() {
-          @Nonnull
+          @NonNull
           @Override
           public StreamResumptionStrategy<Color, Money> createNew() {
             return this;
           }
 
-          @Nonnull
+          @NonNull
           @Override
           public Money processResponse(Money response) {
             return response;
diff --git a/gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonCallContext.java b/gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonCallContext.java
index ad0164fed0..5dd74b129c 100644
--- a/gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonCallContext.java
+++ b/gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonCallContext.java
@@ -55,7 +55,7 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -587,7 +587,7 @@ public HttpJsonCallContext withDeadline(org.threeten.bp.Instant newDeadline) {
     return withCallOptions(builder.setDeadline(newDeadline).build());
   }
 
-  @Nonnull
+  @NonNull
   @Override
   public ApiTracer getTracer() {
     if (tracer == null) {
@@ -598,7 +598,7 @@ public ApiTracer getTracer() {
 
   /** {@inheritDoc} */
   @Override
-  public HttpJsonCallContext withTracer(@Nonnull ApiTracer newTracer) {
+  public HttpJsonCallContext withTracer(@NonNull ApiTracer newTracer) {
     Preconditions.checkNotNull(newTracer);
 
     return new HttpJsonCallContext(
diff --git a/gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonCallableFactory.java b/gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonCallableFactory.java
index 33e2ff886e..af4dcff840 100644
--- a/gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonCallableFactory.java
+++ b/gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonCallableFactory.java
@@ -48,7 +48,7 @@
 import com.google.common.base.Preconditions;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /** Class with utility methods to create http/json-based direct callables. */
 public class HttpJsonCallableFactory {
@@ -228,7 +228,7 @@ ServerStreamingCallable<RequestT, ResponseT> createServerStreamingCallable(
   }
 
   @InternalApi("Visible for testing")
-  static SpanName getSpanName(@Nonnull ApiMethodDescriptor<?, ?> methodDescriptor) {
+  static SpanName getSpanName(@NonNull ApiMethodDescriptor<?, ?> methodDescriptor) {
     Matcher matcher = FULL_METHOD_NAME_REGEX.matcher(methodDescriptor.getFullMethodName());
 
     Preconditions.checkArgument(matcher.matches(), "Invalid fullMethodName");
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/batching/BatcherImpl.java b/gax-java/gax/src/main/java/com/google/api/gax/batching/BatcherImpl.java
index a69ab7c411..1435fe8ed5 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/batching/BatcherImpl.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/batching/BatcherImpl.java
@@ -64,7 +64,7 @@
 import java.util.concurrent.TimeoutException;
 import java.util.logging.Level;
 import java.util.logging.Logger;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -500,7 +500,7 @@ void add(
       totalThrottledTimeMs += throttledTimeMs;
     }
 
-    void setResponseFuture(@Nonnull ApiFuture<ResponseT> responseFuture) {
+    void setResponseFuture(@NonNull ApiFuture<ResponseT> responseFuture) {
       Preconditions.checkNotNull(responseFuture);
       this.responseFuture = responseFuture;
     }
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/retrying/NoopRetryingContext.java b/gax-java/gax/src/main/java/com/google/api/gax/retrying/NoopRetryingContext.java
index 840918ed31..3529c52a95 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/retrying/NoopRetryingContext.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/retrying/NoopRetryingContext.java
@@ -36,7 +36,7 @@
 import com.google.api.gax.tracing.ApiTracer;
 import com.google.api.gax.tracing.BaseApiTracer;
 import java.util.Set;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * Backwards compatibility class to aid in transition to adding operation state to {@link
@@ -48,7 +48,7 @@ public static RetryingContext create() {
   }
 
   /** {@inheritDoc} */
-  @Nonnull
+  @NonNull
   @Override
   public ApiTracer getTracer() {
     return BaseApiTracer.getInstance();
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/retrying/RetryingContext.java b/gax-java/gax/src/main/java/com/google/api/gax/retrying/RetryingContext.java
index 4a745f0a7c..263ff293af 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/retrying/RetryingContext.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/retrying/RetryingContext.java
@@ -33,7 +33,7 @@
 import com.google.api.gax.rpc.StatusCode;
 import com.google.api.gax.tracing.ApiTracer;
 import java.util.Set;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -44,7 +44,7 @@
 @BetaApi("The surface for passing per operation state is not yet stable")
 public interface RetryingContext {
   /** Returns the {@link ApiTracer} associated with the current operation. */
-  @Nonnull
+  @NonNull
   ApiTracer getTracer();
 
   /**
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/retrying/RetryingExecutorWithContext.java b/gax-java/gax/src/main/java/com/google/api/gax/retrying/RetryingExecutorWithContext.java
index f19ba56079..fb9200edbc 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/retrying/RetryingExecutorWithContext.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/retrying/RetryingExecutorWithContext.java
@@ -32,7 +32,7 @@
 import com.google.api.core.BetaApi;
 import com.google.api.core.InternalExtensionOnly;
 import java.util.concurrent.Callable;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * A {@link RetryingExecutor} that accepts a per-operation context.
@@ -45,5 +45,5 @@
 @InternalExtensionOnly
 public interface RetryingExecutorWithContext<ResponseT> extends RetryingExecutor<ResponseT> {
   RetryingFuture<ResponseT> createFuture(
-      @Nonnull Callable<ResponseT> callable, @Nonnull RetryingContext context);
+      @NonNull Callable<ResponseT> callable, @NonNull RetryingContext context);
 }
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/retrying/StreamResumptionStrategy.java b/gax-java/gax/src/main/java/com/google/api/gax/retrying/StreamResumptionStrategy.java
index 3178a866c9..9fcdd08cd5 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/retrying/StreamResumptionStrategy.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/retrying/StreamResumptionStrategy.java
@@ -29,7 +29,7 @@
  */
 package com.google.api.gax.retrying;
 
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -41,7 +41,7 @@
 public interface StreamResumptionStrategy<RequestT, ResponseT> {
 
   /** Creates a new instance of this StreamResumptionStrategy without accumulated state */
-  @Nonnull
+  @NonNull
   StreamResumptionStrategy<RequestT, ResponseT> createNew();
 
   /**
@@ -58,7 +58,7 @@ public interface StreamResumptionStrategy<RequestT, ResponseT> {
    *       through this method.
    * </ol>
    */
-  @Nonnull
+  @NonNull
   ResponseT processResponse(ResponseT response);
 
   /**
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/rpc/ApiCallContext.java b/gax-java/gax/src/main/java/com/google/api/gax/rpc/ApiCallContext.java
index fb14424d65..4a034a6327 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/rpc/ApiCallContext.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/rpc/ApiCallContext.java
@@ -41,7 +41,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -173,7 +173,7 @@ public interface ApiCallContext extends RetryingContext {
    * events like retries.
    */
   @BetaApi("The surface for tracing is not stable yet and may change in the future")
-  @Nonnull
+  @NonNull
   ApiTracer getTracer();
 
   /**
@@ -185,7 +185,7 @@ public interface ApiCallContext extends RetryingContext {
    * @param tracer the {@link ApiTracer} to set.
    */
   @BetaApi("The surface for tracing is not stable yet and may change in the future")
-  ApiCallContext withTracer(@Nonnull ApiTracer tracer);
+  ApiCallContext withTracer(@NonNull ApiTracer tracer);
 
   /**
    * Returns a new ApiCallContext with the given {@link RetrySettings} set.
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientContext.java b/gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientContext.java
index a5058e019f..2e9d8b6d90 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientContext.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientContext.java
@@ -58,7 +58,7 @@
 import java.util.Set;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -101,14 +101,12 @@ public abstract class ClientContext {
   public abstract Watchdog getStreamWatchdog();
 
   /** This method is obsolete. Use {@link #getStreamWatchdogCheckIntervalDuration()} instead. */
-  @Nonnull
   @ObsoleteApi("Use getStreamWatchdogCheckIntervalDuration() instead")
-  public final org.threeten.bp.Duration getStreamWatchdogCheckInterval() {
+  public final org.threeten.bp.@NonNull Duration getStreamWatchdogCheckInterval() {
     return toThreetenDuration(getStreamWatchdogCheckIntervalDuration());
   }
 
-  @Nonnull
-  public abstract java.time.Duration getStreamWatchdogCheckIntervalDuration();
+  public abstract java.time.@NonNull Duration getStreamWatchdogCheckIntervalDuration();
 
   @Nullable
   public abstract String getUniverseDomain();
@@ -124,7 +122,7 @@ public final org.threeten.bp.Duration getStreamWatchdogCheckInterval() {
 
   /** Gets the {@link ApiTracerFactory} that will be used to generate traces for operations. */
   @BetaApi("The surface for tracing is not stable yet and may change in the future.")
-  @Nonnull
+  @NonNull
   public abstract ApiTracerFactory getTracerFactory();
 
   /**
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientSettings.java b/gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientSettings.java
index 78ac3f803d..5253780ad2 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientSettings.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientSettings.java
@@ -39,7 +39,7 @@
 import com.google.common.base.MoreObjects;
 import java.io.IOException;
 import java.util.concurrent.Executor;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -113,14 +113,12 @@ public final WatchdogProvider getWatchdogProvider() {
   }
 
   /** This method is obsolete. Use {@link #getWatchdogCheckIntervalDuration()} instead. */
-  @Nonnull
   @ObsoleteApi("Use getWatchdogCheckIntervalDuration() instead")
-  public final org.threeten.bp.Duration getWatchdogCheckInterval() {
+  public final org.threeten.bp.@NonNull Duration getWatchdogCheckInterval() {
     return stubSettings.getStreamWatchdogCheckInterval();
   }
 
-  @Nonnull
-  public final java.time.Duration getWatchdogCheckIntervalDuration() {
+  public final java.time.@NonNull Duration getWatchdogCheckIntervalDuration() {
     return stubSettings.getStreamWatchdogCheckIntervalDuration();
   }
 
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/rpc/FixedWatchdogProvider.java b/gax-java/gax/src/main/java/com/google/api/gax/rpc/FixedWatchdogProvider.java
index 74484ef50a..ead51b317c 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/rpc/FixedWatchdogProvider.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/rpc/FixedWatchdogProvider.java
@@ -34,7 +34,7 @@
 import com.google.api.core.ObsoleteApi;
 import java.time.Duration;
 import java.util.concurrent.ScheduledExecutorService;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -62,7 +62,7 @@ public boolean needsClock() {
   }
 
   @Override
-  public WatchdogProvider withClock(@Nonnull ApiClock clock) {
+  public WatchdogProvider withClock(@NonNull ApiClock clock) {
     throw new UnsupportedOperationException("FixedWatchdogProvider doesn't need a clock");
   }
 
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/rpc/InstantiatingWatchdogProvider.java b/gax-java/gax/src/main/java/com/google/api/gax/rpc/InstantiatingWatchdogProvider.java
index 725c2a02e8..1fa3beb4e9 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/rpc/InstantiatingWatchdogProvider.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/rpc/InstantiatingWatchdogProvider.java
@@ -36,7 +36,7 @@
 import com.google.api.core.ObsoleteApi;
 import com.google.common.base.Preconditions;
 import java.util.concurrent.ScheduledExecutorService;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -70,7 +70,7 @@ public boolean needsClock() {
   }
 
   @Override
-  public WatchdogProvider withClock(@Nonnull ApiClock clock) {
+  public WatchdogProvider withClock(@NonNull ApiClock clock) {
     return new InstantiatingWatchdogProvider(
         Preconditions.checkNotNull(clock), executor, checkInterval);
   }
@@ -85,12 +85,12 @@ public boolean needsCheckInterval() {
    */
   @Override
   @ObsoleteApi("Use withCheckIntervalDuration(java.time.Duration) instead")
-  public WatchdogProvider withCheckInterval(@Nonnull org.threeten.bp.Duration checkInterval) {
+  public WatchdogProvider withCheckInterval(org.threeten.bp.@NonNull Duration checkInterval) {
     return withCheckIntervalDuration(toJavaTimeDuration(checkInterval));
   }
 
   @Override
-  public WatchdogProvider withCheckIntervalDuration(@Nonnull java.time.Duration checkInterval) {
+  public WatchdogProvider withCheckIntervalDuration(java.time.@NonNull Duration checkInterval) {
     return new InstantiatingWatchdogProvider(
         clock, executor, Preconditions.checkNotNull(checkInterval));
   }
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/rpc/ServerStream.java b/gax-java/gax/src/main/java/com/google/api/gax/rpc/ServerStream.java
index d1f9848631..2700a0a1f1 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/rpc/ServerStream.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/rpc/ServerStream.java
@@ -33,7 +33,7 @@
 import java.util.Iterator;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * A blocking Iterable-style wrapper around server stream responses.
@@ -81,7 +81,7 @@ ResponseObserver<V> observer() {
 
   /** {@inheritDoc} */
   @Override
-  @Nonnull
+  @NonNull
   public Iterator<V> iterator() {
     if (consumed) {
       throw new IllegalStateException("Iterator already consumed");
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/rpc/ServerStreamingCallSettings.java b/gax-java/gax/src/main/java/com/google/api/gax/rpc/ServerStreamingCallSettings.java
index cbba46485f..6a08a765e3 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/rpc/ServerStreamingCallSettings.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/rpc/ServerStreamingCallSettings.java
@@ -43,7 +43,7 @@
 import com.google.common.collect.Sets;
 import java.time.Duration;
 import java.util.Set;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * A settings class to configure a {@link ServerStreamingCallable}.
@@ -80,12 +80,12 @@
 public final class ServerStreamingCallSettings<RequestT, ResponseT>
     extends StreamingCallSettings<RequestT, ResponseT> {
 
-  @Nonnull private final Set<Code> retryableCodes;
-  @Nonnull private final RetrySettings retrySettings;
-  @Nonnull private final StreamResumptionStrategy<RequestT, ResponseT> resumptionStrategy;
+  @NonNull private final Set<Code> retryableCodes;
+  @NonNull private final RetrySettings retrySettings;
+  @NonNull private final StreamResumptionStrategy<RequestT, ResponseT> resumptionStrategy;
 
-  @Nonnull private final java.time.Duration idleTimeout;
-  @Nonnull private final java.time.Duration waitTimeout;
+  private final java.time.@NonNull Duration idleTimeout;
+  private final java.time.@NonNull Duration waitTimeout;
 
   private ServerStreamingCallSettings(Builder<RequestT, ResponseT> builder) {
     this.retryableCodes = ImmutableSet.copyOf(builder.retryableCodes);
@@ -99,7 +99,7 @@ private ServerStreamingCallSettings(Builder<RequestT, ResponseT> builder) {
    * See the class documentation of {@link ServerStreamingCallSettings} for a description of what
    * retryableCodes do.
    */
-  @Nonnull
+  @NonNull
   public Set<Code> getRetryableCodes() {
     return retryableCodes;
   }
@@ -108,7 +108,7 @@ public Set<Code> getRetryableCodes() {
    * See the class documentation of {@link ServerStreamingCallSettings} for a description of what
    * retrySettings do.
    */
-  @Nonnull
+  @NonNull
   public RetrySettings getRetrySettings() {
     return retrySettings;
   }
@@ -117,15 +117,14 @@ public RetrySettings getRetrySettings() {
    * See the class documentation of {@link ServerStreamingCallSettings} and {@link
    * StreamResumptionStrategy} for a description of what the StreamResumptionStrategy does.
    */
-  @Nonnull
+  @NonNull
   public StreamResumptionStrategy<RequestT, ResponseT> getResumptionStrategy() {
     return resumptionStrategy;
   }
 
   /** This method is obsolete. Use {@link #getIdleTimeoutDuration()} instead. */
-  @Nonnull
   @ObsoleteApi("Use getIdleTimeoutDuration() instead")
-  public org.threeten.bp.Duration getIdleTimeout() {
+  public org.threeten.bp.@NonNull Duration getIdleTimeout() {
     return toThreetenDuration(getIdleTimeoutDuration());
   }
 
@@ -133,15 +132,13 @@ public org.threeten.bp.Duration getIdleTimeout() {
    * See the class documentation of {@link ServerStreamingCallSettings} for a description of what
    * the {@link #idleTimeout} does.
    */
-  @Nonnull
-  public java.time.Duration getIdleTimeoutDuration() {
+  public java.time.@NonNull Duration getIdleTimeoutDuration() {
     return idleTimeout;
   }
 
   /** This method is obsolete. Use {@link #getWaitTimeoutDuration()} instead. */
-  @Nonnull
   @ObsoleteApi("Use getWaitTimeoutDuration() instead")
-  public org.threeten.bp.Duration getWaitTimeout() {
+  public org.threeten.bp.@NonNull Duration getWaitTimeout() {
     return toThreetenDuration(getWaitTimeoutDuration());
   }
 
@@ -149,8 +146,7 @@ public org.threeten.bp.Duration getWaitTimeout() {
    * See the class documentation of {@link ServerStreamingCallSettings} for a description of what
    * the {@link #waitTimeout} does.
    */
-  @Nonnull
-  public java.time.Duration getWaitTimeoutDuration() {
+  public java.time.@NonNull Duration getWaitTimeoutDuration() {
     return waitTimeout;
   }
 
@@ -174,13 +170,13 @@ public String toString() {
 
   public static class Builder<RequestT, ResponseT>
       extends StreamingCallSettings.Builder<RequestT, ResponseT> {
-    @Nonnull private Set<StatusCode.Code> retryableCodes;
-    @Nonnull private RetrySettings.Builder retrySettingsBuilder;
-    @Nonnull private StreamResumptionStrategy<RequestT, ResponseT> resumptionStrategy;
+    @NonNull private Set<StatusCode.Code> retryableCodes;
+    private RetrySettings.@NonNull Builder retrySettingsBuilder;
+    @NonNull private StreamResumptionStrategy<RequestT, ResponseT> resumptionStrategy;
 
-    @Nonnull private java.time.Duration idleTimeout;
+    private java.time.@NonNull Duration idleTimeout;
 
-    @Nonnull private java.time.Duration waitTimeout;
+    private java.time.@NonNull Duration waitTimeout;
 
     /** Initialize the builder with default settings */
     private Builder() {
@@ -221,7 +217,7 @@ public Builder<RequestT, ResponseT> setRetryableCodes(Set<Code> retryableCodes)
       return this;
     }
 
-    @Nonnull
+    @NonNull
     public Set<Code> getRetryableCodes() {
       return retryableCodes;
     }
@@ -249,13 +245,13 @@ public RetrySettings.Builder retrySettings() {
      *
      * @see #retrySettings()
      */
-    public Builder<RequestT, ResponseT> setRetrySettings(@Nonnull RetrySettings retrySettings) {
+    public Builder<RequestT, ResponseT> setRetrySettings(@NonNull RetrySettings retrySettings) {
       Preconditions.checkNotNull(retrySettings);
       this.retrySettingsBuilder = retrySettings.toBuilder();
       return this;
     }
 
-    @Nonnull
+    @NonNull
     public RetrySettings getRetrySettings() {
       return retrySettingsBuilder.build();
     }
@@ -266,13 +262,13 @@ public RetrySettings getRetrySettings() {
      */
     @ObsoleteApi("Use setSimpleTimeoutNoRetriesDuration(java.time.Duration) instead")
     public Builder<RequestT, ResponseT> setSimpleTimeoutNoRetries(
-        @Nonnull org.threeten.bp.Duration timeout) {
+        org.threeten.bp.@NonNull Duration timeout) {
       return setSimpleTimeoutNoRetriesDuration(toJavaTimeDuration(timeout));
     }
 
     /** Disables retries and sets the overall timeout. */
     public Builder<RequestT, ResponseT> setSimpleTimeoutNoRetriesDuration(
-        @Nonnull java.time.Duration timeout) {
+        java.time.@NonNull Duration timeout) {
       setRetryableCodes();
       setRetrySettings(
           RetrySettings.newBuilder()
@@ -294,33 +290,31 @@ public Builder<RequestT, ResponseT> setSimpleTimeoutNoRetriesDuration(
      * StreamResumptionStrategy does.
      */
     public Builder<RequestT, ResponseT> setResumptionStrategy(
-        @Nonnull StreamResumptionStrategy<RequestT, ResponseT> resumptionStrategy) {
+        @NonNull StreamResumptionStrategy<RequestT, ResponseT> resumptionStrategy) {
       Preconditions.checkNotNull(resumptionStrategy);
       this.resumptionStrategy = Preconditions.checkNotNull(resumptionStrategy);
       return this;
     }
 
-    @Nonnull
+    @NonNull
     public StreamResumptionStrategy<RequestT, ResponseT> getResumptionStrategy() {
       return resumptionStrategy;
     }
 
     /** This method is obsolete. Use {@link #getIdleTimeoutDuration()} instead. */
-    @Nonnull
     @ObsoleteApi("Use getIdleTimeoutDuration() instead")
-    public org.threeten.bp.Duration getIdleTimeout() {
+    public org.threeten.bp.@NonNull Duration getIdleTimeout() {
       return toThreetenDuration(getIdleTimeoutDuration());
     }
 
-    @Nonnull
-    public java.time.Duration getIdleTimeoutDuration() {
+    public java.time.@NonNull Duration getIdleTimeoutDuration() {
       return idleTimeout;
     }
 
     /** This method is obsolete. Use {@link #setIdleTimeoutDuration(Duration)} instead. */
     @ObsoleteApi("Use setIdleTimeoutDuration(java.time.Duration) instead")
     public Builder<RequestT, ResponseT> setIdleTimeout(
-        @Nonnull org.threeten.bp.Duration idleTimeout) {
+        org.threeten.bp.@NonNull Duration idleTimeout) {
       return setIdleTimeoutDuration(toJavaTimeDuration(idleTimeout));
     }
 
@@ -329,27 +323,25 @@ public Builder<RequestT, ResponseT> setIdleTimeout(
      * {@link java.time.Duration#ZERO} disables the check for abandoned streams.
      */
     public Builder<RequestT, ResponseT> setIdleTimeoutDuration(
-        @Nonnull java.time.Duration idleTimeout) {
+        java.time.@NonNull Duration idleTimeout) {
       this.idleTimeout = Preconditions.checkNotNull(idleTimeout);
       return this;
     }
 
     /** This method is obsolete. Use {@link #getWaitTimeoutDuration()} instead. */
-    @Nonnull
     @ObsoleteApi("Use getWaitTimeoutDuration() instead")
-    public org.threeten.bp.Duration getWaitTimeout() {
+    public org.threeten.bp.@NonNull Duration getWaitTimeout() {
       return toThreetenDuration(getWaitTimeoutDuration());
     }
 
-    @Nonnull
-    public java.time.Duration getWaitTimeoutDuration() {
+    public java.time.@NonNull Duration getWaitTimeoutDuration() {
       return waitTimeout;
     }
 
     /** This method is obsolete. Use {@link #setWaitTimeoutDuration(java.time.Duration)} instead. */
     @ObsoleteApi("Use setWaitTimeoutDuration(java.time.Duration) instead")
     public Builder<RequestT, ResponseT> setWaitTimeout(
-        @Nonnull org.threeten.bp.Duration waitTimeout) {
+        org.threeten.bp.@NonNull Duration waitTimeout) {
       return setWaitTimeoutDuration(toJavaTimeDuration(waitTimeout));
     }
 
@@ -358,7 +350,7 @@ public Builder<RequestT, ResponseT> setWaitTimeout(
      * java.time.Duration#ZERO} disables the check for abandoned streams.
      */
     public Builder<RequestT, ResponseT> setWaitTimeoutDuration(
-        @Nonnull java.time.Duration waitTimeout) {
+        java.time.@NonNull Duration waitTimeout) {
       this.waitTimeout = waitTimeout;
       return this;
     }
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/rpc/StubSettings.java b/gax-java/gax/src/main/java/com/google/api/gax/rpc/StubSettings.java
index 0342bea45d..60240abefc 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/rpc/StubSettings.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/rpc/StubSettings.java
@@ -51,7 +51,7 @@
 import com.google.common.base.Preconditions;
 import java.io.IOException;
 import java.util.concurrent.Executor;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -77,11 +77,11 @@ public abstract class StubSettings<SettingsT extends StubSettings<SettingsT>> {
   private final String quotaProjectId;
   @Nullable private final String gdchApiAudience;
   @Nullable private final WatchdogProvider streamWatchdogProvider;
-  @Nonnull private final java.time.Duration streamWatchdogCheckInterval;
-  @Nonnull private final ApiTracerFactory tracerFactory;
+  private final java.time.@NonNull Duration streamWatchdogCheckInterval;
+  @NonNull private final ApiTracerFactory tracerFactory;
   // Track if deprecated setExecutorProvider is called
   private boolean deprecatedExecutorProviderSet;
-  @Nonnull private final EndpointContext endpointContext;
+  @NonNull private final EndpointContext endpointContext;
 
   /**
    * Indicate when creating transport whether it is allowed to use mTLS endpoint instead of the
@@ -207,14 +207,12 @@ public final WatchdogProvider getStreamWatchdogProvider() {
   }
 
   /** This method is obsolete. Use {@link #getStreamWatchdogCheckIntervalDuration()} instead. */
-  @Nonnull
   @ObsoleteApi("Use getStreamWatchdogCheckIntervalDuration() instead")
-  public final org.threeten.bp.Duration getStreamWatchdogCheckInterval() {
+  public final org.threeten.bp.@NonNull Duration getStreamWatchdogCheckInterval() {
     return toThreetenDuration(getStreamWatchdogCheckIntervalDuration());
   }
 
-  @Nonnull
-  public final java.time.Duration getStreamWatchdogCheckIntervalDuration() {
+  public final java.time.@NonNull Duration getStreamWatchdogCheckIntervalDuration() {
     return streamWatchdogCheckInterval;
   }
 
@@ -223,7 +221,7 @@ public final java.time.Duration getStreamWatchdogCheckIntervalDuration() {
    * operations.
    */
   @BetaApi("The surface for tracing is not stable yet and may change in the future.")
-  @Nonnull
+  @NonNull
   public ApiTracerFactory getTracerFactory() {
     return tracerFactory;
   }
@@ -272,8 +270,8 @@ public abstract static class Builder<
     private String quotaProjectId;
     @Nullable private String gdchApiAudience;
     @Nullable private WatchdogProvider streamWatchdogProvider;
-    @Nonnull private java.time.Duration streamWatchdogCheckInterval;
-    @Nonnull private ApiTracerFactory tracerFactory;
+    private java.time.@NonNull Duration streamWatchdogCheckInterval;
+    @NonNull private ApiTracerFactory tracerFactory;
     private boolean deprecatedExecutorProviderSet;
     private String universeDomain;
     private final EndpointContext endpointContext;
@@ -536,7 +534,7 @@ public B setQuotaProjectId(String quotaProjectId) {
      * #setStreamWatchdogCheckIntervalDuration(java.time.Duration)} instead.
      */
     @ObsoleteApi("Use setStreamWatchdogCheckIntervalDuration(java.time.Duration) instead")
-    public B setStreamWatchdogCheckInterval(@Nonnull org.threeten.bp.Duration checkInterval) {
+    public B setStreamWatchdogCheckInterval(org.threeten.bp.@NonNull Duration checkInterval) {
       return setStreamWatchdogCheckIntervalDuration(toJavaTimeDuration(checkInterval));
     }
 
@@ -544,7 +542,7 @@ public B setStreamWatchdogCheckInterval(@Nonnull org.threeten.bp.Duration checkI
      * Sets how often the {@link Watchdog} will check ongoing streaming RPCs. Defaults to 10 secs.
      * Use {@link java.time.Duration#ZERO} to disable.
      */
-    public B setStreamWatchdogCheckIntervalDuration(@Nonnull java.time.Duration checkInterval) {
+    public B setStreamWatchdogCheckIntervalDuration(java.time.@NonNull Duration checkInterval) {
       Preconditions.checkNotNull(checkInterval);
       this.streamWatchdogCheckInterval = checkInterval;
       return self();
@@ -568,7 +566,7 @@ public B setGdchApiAudience(String gdchApiAudience) {
      * @param tracerFactory an instance of {@link ApiTracerFactory} to set.
      */
     @BetaApi("The surface for tracing is not stable yet and may change in the future.")
-    public B setTracerFactory(@Nonnull ApiTracerFactory tracerFactory) {
+    public B setTracerFactory(@NonNull ApiTracerFactory tracerFactory) {
       Preconditions.checkNotNull(tracerFactory);
       this.tracerFactory = tracerFactory;
       return self();
@@ -646,13 +644,12 @@ public org.threeten.bp.Duration getStreamWatchdogCheckInterval() {
       return toThreetenDuration(getStreamWatchdogCheckIntervalDuration());
     }
 
-    @Nonnull
-    public java.time.Duration getStreamWatchdogCheckIntervalDuration() {
+    public java.time.@NonNull Duration getStreamWatchdogCheckIntervalDuration() {
       return Preconditions.checkNotNull(streamWatchdogCheckInterval);
     }
 
     @BetaApi("The surface for tracing is not stable yet and may change in the future.")
-    @Nonnull
+    @NonNull
     public ApiTracerFactory getTracerFactory() {
       return tracerFactory;
     }
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/rpc/Watchdog.java b/gax-java/gax/src/main/java/com/google/api/gax/rpc/Watchdog.java
index 69ca5d1eca..b86aa5e99d 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/rpc/Watchdog.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/rpc/Watchdog.java
@@ -49,7 +49,7 @@
 import java.util.concurrent.TimeoutException;
 import java.util.logging.Level;
 import java.util.logging.Logger;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * Prevents the streams from hanging indefinitely. This middleware garbage collects idle streams in
@@ -120,16 +120,17 @@ private void start() {
       "Use watchDuration(ResponseObserver, java.time.Duration, java.time.Duration) instead")
   public <ResponseT> ResponseObserver<ResponseT> watch(
       ResponseObserver<ResponseT> innerObserver,
-      @Nonnull org.threeten.bp.Duration waitTimeout,
-      @Nonnull org.threeten.bp.Duration idleTimeout) {
+      org.threeten.bp.@NonNull Duration waitTimeout,
+      org.threeten.bp.@NonNull Duration idleTimeout) {
     return watchDuration(
         innerObserver, toJavaTimeDuration(waitTimeout), toJavaTimeDuration(idleTimeout));
   }
+
   /** Wraps the target observer with timing constraints. */
   public <ResponseT> ResponseObserver<ResponseT> watchDuration(
       ResponseObserver<ResponseT> innerObserver,
-      @Nonnull java.time.Duration waitTimeout,
-      @Nonnull java.time.Duration idleTimeout) {
+      java.time.@NonNull Duration waitTimeout,
+      java.time.@NonNull Duration idleTimeout) {
     Preconditions.checkNotNull(innerObserver, "innerObserver can't be null");
     Preconditions.checkNotNull(waitTimeout, "waitTimeout can't be null");
     Preconditions.checkNotNull(idleTimeout, "idleTimeout can't be null");
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/rpc/WatchdogProvider.java b/gax-java/gax/src/main/java/com/google/api/gax/rpc/WatchdogProvider.java
index a31fc7b6f4..6a92e7bf51 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/rpc/WatchdogProvider.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/rpc/WatchdogProvider.java
@@ -34,12 +34,12 @@
 import com.google.api.core.ApiClock;
 import com.google.api.core.ObsoleteApi;
 import java.util.concurrent.ScheduledExecutorService;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 public interface WatchdogProvider {
   boolean needsClock();
 
-  WatchdogProvider withClock(@Nonnull ApiClock clock);
+  WatchdogProvider withClock(@NonNull ApiClock clock);
 
   boolean needsCheckInterval();
 
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/tracing/OpencensusTracer.java b/gax-java/gax/src/main/java/com/google/api/gax/tracing/OpencensusTracer.java
index c9f6b7cfc7..f8e6c493c5 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/tracing/OpencensusTracer.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/tracing/OpencensusTracer.java
@@ -49,7 +49,7 @@
 import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicLong;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * Implementation of {@link ApiTracer} that uses OpenCensus.
@@ -222,7 +222,7 @@ public class OpencensusTracer extends BaseApiTracer {
   private long totalReceivedMessages = 0;
 
   OpencensusTracer(
-      @Nonnull Tracer tracer, @Nonnull Span span, @Nonnull OperationType operationType) {
+      @NonNull Tracer tracer, @NonNull Span span, @NonNull OperationType operationType) {
     this.tracer = Preconditions.checkNotNull(tracer, "tracer can't be null");
     this.span = Preconditions.checkNotNull(span, "span can't be null");
     this.operationType = Preconditions.checkNotNull(operationType, "operationType can't be null");
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/tracing/OpencensusTracerFactory.java b/gax-java/gax/src/main/java/com/google/api/gax/tracing/OpencensusTracerFactory.java
index b9966b1f51..81434a1ac4 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/tracing/OpencensusTracerFactory.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/tracing/OpencensusTracerFactory.java
@@ -38,7 +38,7 @@
 import io.opencensus.trace.Tracer;
 import io.opencensus.trace.Tracing;
 import java.util.Map;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * A {@link ApiTracerFactory} to build instances of {@link OpencensusTracer}.
@@ -50,8 +50,8 @@
  */
 @InternalApi("For google-cloud-java client use only")
 public final class OpencensusTracerFactory extends BaseApiTracerFactory {
-  @Nonnull private final Tracer internalTracer;
-  @Nonnull private final Map<String, AttributeValue> spanAttributes;
+  @NonNull private final Tracer internalTracer;
+  @NonNull private final Map<String, AttributeValue> spanAttributes;
 
   /**
    * Instantiates a new instance capturing the {@link io.opencensus.trace.Tracer} in {@code
@@ -82,7 +82,7 @@ public OpencensusTracerFactory(Map<String, String> spanAttributes) {
    * @param internalTracer the Opencensus tracer to wrap.
    */
   @InternalApi("Visible for testing")
-  OpencensusTracerFactory(Tracer internalTracer, @Nonnull Map<String, String> spanAttributes) {
+  OpencensusTracerFactory(Tracer internalTracer, @NonNull Map<String, String> spanAttributes) {
     this.internalTracer =
         Preconditions.checkNotNull(internalTracer, "internalTracer can't be null");
     ImmutableMap.Builder<String, AttributeValue> formattedSpanAttributes = ImmutableMap.builder();
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TraceFinisher.java b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TraceFinisher.java
index 292a827759..595b131023 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TraceFinisher.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TraceFinisher.java
@@ -32,13 +32,13 @@
 import com.google.api.core.ApiFutureCallback;
 import com.google.common.base.Preconditions;
 import java.util.concurrent.CancellationException;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /** An {@link ApiFutureCallback} to mark a started operation trace as finished. */
 class TraceFinisher<T> implements ApiFutureCallback<T> {
   private final ApiTracer tracer;
 
-  TraceFinisher(@Nonnull ApiTracer tracer) {
+  TraceFinisher(@NonNull ApiTracer tracer) {
     this.tracer = Preconditions.checkNotNull(tracer, "tracer can't be null");
   }
 
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedBidiCallable.java b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedBidiCallable.java
index fd2172752d..1ab46095bc 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedBidiCallable.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedBidiCallable.java
@@ -40,7 +40,7 @@
 import com.google.common.base.Preconditions;
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.atomic.AtomicBoolean;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * A wrapper callable that will wrap a callable chain in a trace.
@@ -52,14 +52,14 @@
 public class TracedBidiCallable<RequestT, ResponseT>
     extends BidiStreamingCallable<RequestT, ResponseT> {
 
-  @Nonnull private final ApiTracerFactory tracerFactory;
-  @Nonnull private final SpanName spanName;
-  @Nonnull private final BidiStreamingCallable<RequestT, ResponseT> innerCallable;
+  @NonNull private final ApiTracerFactory tracerFactory;
+  @NonNull private final SpanName spanName;
+  @NonNull private final BidiStreamingCallable<RequestT, ResponseT> innerCallable;
 
   public TracedBidiCallable(
-      @Nonnull BidiStreamingCallable<RequestT, ResponseT> innerCallable,
-      @Nonnull ApiTracerFactory tracerFactory,
-      @Nonnull SpanName spanName) {
+      @NonNull BidiStreamingCallable<RequestT, ResponseT> innerCallable,
+      @NonNull ApiTracerFactory tracerFactory,
+      @NonNull SpanName spanName) {
     this.tracerFactory = Preconditions.checkNotNull(tracerFactory, "tracerFactory can't be null");
     this.spanName = Preconditions.checkNotNull(spanName, "spanName can't be null");
     this.innerCallable = Preconditions.checkNotNull(innerCallable, "innerCallable can't be null");
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedClientStreamingCallable.java b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedClientStreamingCallable.java
index 773efe2dea..cb41c7ccf2 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedClientStreamingCallable.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedClientStreamingCallable.java
@@ -38,7 +38,7 @@
 import com.google.common.base.Preconditions;
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.atomic.AtomicReference;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * A wrapper callable that will wrap a callable chain in a trace.
@@ -57,9 +57,9 @@ public class TracedClientStreamingCallable<RequestT, ResponseT>
   private final SpanName spanName;
 
   public TracedClientStreamingCallable(
-      @Nonnull ClientStreamingCallable<RequestT, ResponseT> innerCallable,
-      @Nonnull ApiTracerFactory tracerFactory,
-      @Nonnull SpanName spanName) {
+      @NonNull ClientStreamingCallable<RequestT, ResponseT> innerCallable,
+      @NonNull ApiTracerFactory tracerFactory,
+      @NonNull SpanName spanName) {
     this.tracerFactory = Preconditions.checkNotNull(tracerFactory, "tracerFactory can't be null");
     this.spanName = Preconditions.checkNotNull(spanName, "spanName can't be null");
     this.innerCallable = Preconditions.checkNotNull(innerCallable, "innerCallable can't be null");
@@ -98,9 +98,9 @@ private static class TracedRequestObserver<RequestT> implements ApiStreamObserve
     private final AtomicReference<Throwable> cancellationCauseHolder;
 
     TracedRequestObserver(
-        @Nonnull ApiTracer tracer,
-        @Nonnull ApiStreamObserver<RequestT> innerObserver,
-        @Nonnull AtomicReference<Throwable> cancellationCauseHolder) {
+        @NonNull ApiTracer tracer,
+        @NonNull ApiStreamObserver<RequestT> innerObserver,
+        @NonNull AtomicReference<Throwable> cancellationCauseHolder) {
       this.tracer = Preconditions.checkNotNull(tracer, "tracer can't be null");
       this.innerObserver = Preconditions.checkNotNull(innerObserver, "innerObserver can't be null");
       this.cancellationCauseHolder =
@@ -137,14 +137,14 @@ public void onCompleted() {
    * close the current trace upon completion of the RPC.
    */
   private static class TracedResponseObserver<RequestT> implements ApiStreamObserver<RequestT> {
-    @Nonnull private final ApiTracer tracer;
-    @Nonnull private final ApiStreamObserver<RequestT> innerObserver;
-    @Nonnull private final AtomicReference<Throwable> cancellationCauseHolder;
+    @NonNull private final ApiTracer tracer;
+    @NonNull private final ApiStreamObserver<RequestT> innerObserver;
+    @NonNull private final AtomicReference<Throwable> cancellationCauseHolder;
 
     TracedResponseObserver(
-        @Nonnull ApiTracer tracer,
-        @Nonnull ApiStreamObserver<RequestT> innerObserver,
-        @Nonnull AtomicReference<Throwable> cancellationCauseHolder) {
+        @NonNull ApiTracer tracer,
+        @NonNull ApiStreamObserver<RequestT> innerObserver,
+        @NonNull AtomicReference<Throwable> cancellationCauseHolder) {
       this.tracer = Preconditions.checkNotNull(tracer, "tracer can't be null");
       this.innerObserver = Preconditions.checkNotNull(innerObserver, "innerObserver can't be null");
       this.cancellationCauseHolder = cancellationCauseHolder;
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedOperationCallable.java b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedOperationCallable.java
index 3b83d7fd75..e95135b048 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedOperationCallable.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedOperationCallable.java
@@ -37,7 +37,7 @@
 import com.google.api.gax.rpc.OperationCallable;
 import com.google.api.gax.tracing.ApiTracerFactory.OperationType;
 import com.google.common.util.concurrent.MoreExecutors;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * This callable wraps a {@link OperationCallable} in a {@link ApiTracer}.
@@ -48,14 +48,14 @@
 public class TracedOperationCallable<RequestT, ResponseT, MetadataT>
     extends OperationCallable<RequestT, ResponseT, MetadataT> {
 
-  private @Nonnull OperationCallable<RequestT, ResponseT, MetadataT> innerCallable;
-  private @Nonnull ApiTracerFactory tracerFactory;
-  private @Nonnull SpanName spanName;
+  private @NonNull OperationCallable<RequestT, ResponseT, MetadataT> innerCallable;
+  private @NonNull ApiTracerFactory tracerFactory;
+  private @NonNull SpanName spanName;
 
   public TracedOperationCallable(
-      @Nonnull OperationCallable<RequestT, ResponseT, MetadataT> innerCallable,
-      @Nonnull ApiTracerFactory tracerFactory,
-      @Nonnull SpanName spanName) {
+      @NonNull OperationCallable<RequestT, ResponseT, MetadataT> innerCallable,
+      @NonNull ApiTracerFactory tracerFactory,
+      @NonNull SpanName spanName) {
     this.innerCallable = innerCallable;
     this.tracerFactory = tracerFactory;
     this.spanName = spanName;
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedResponseObserver.java b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedResponseObserver.java
index ba72d2f5b7..bc6ab4d5b6 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedResponseObserver.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedResponseObserver.java
@@ -34,7 +34,7 @@
 import com.google.api.gax.rpc.StreamController;
 import com.google.common.base.Preconditions;
 import java.util.concurrent.atomic.AtomicBoolean;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * A {@link ResponseObserver} to mark a started operation trace as finished.
@@ -50,14 +50,14 @@ class TracedResponseObserver<ResponseT> implements ResponseObserver<ResponseT> {
   private AtomicBoolean wasCancelled;
 
   TracedResponseObserver(
-      @Nonnull ApiTracer tracer, @Nonnull ResponseObserver<ResponseT> innerObserver) {
+      @NonNull ApiTracer tracer, @NonNull ResponseObserver<ResponseT> innerObserver) {
     this(tracer, innerObserver, new AtomicBoolean());
   }
 
   TracedResponseObserver(
-      @Nonnull ApiTracer tracer,
-      @Nonnull ResponseObserver<ResponseT> innerObserver,
-      @Nonnull AtomicBoolean wasCancelled) {
+      @NonNull ApiTracer tracer,
+      @NonNull ResponseObserver<ResponseT> innerObserver,
+      @NonNull AtomicBoolean wasCancelled) {
     this.tracer = Preconditions.checkNotNull(tracer, "tracer");
     this.innerObserver = Preconditions.checkNotNull(innerObserver, "innerObserver");
     this.wasCancelled = Preconditions.checkNotNull(wasCancelled, "wasCancelled");
diff --git a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedServerStreamingCallable.java b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedServerStreamingCallable.java
index e46520e616..c136345456 100644
--- a/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedServerStreamingCallable.java
+++ b/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedServerStreamingCallable.java
@@ -36,7 +36,7 @@
 import com.google.api.gax.rpc.ServerStreamingCallable;
 import com.google.api.gax.tracing.ApiTracerFactory.OperationType;
 import com.google.common.base.Preconditions;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * A wrapper callable that will wrap a callable chain in a trace.
@@ -48,14 +48,14 @@
 public final class TracedServerStreamingCallable<RequestT, ResponseT>
     extends ServerStreamingCallable<RequestT, ResponseT> {
 
-  @Nonnull private final ApiTracerFactory tracerFactory;
-  @Nonnull private final SpanName spanName;
-  @Nonnull private final ServerStreamingCallable<RequestT, ResponseT> innerCallable;
+  @NonNull private final ApiTracerFactory tracerFactory;
+  @NonNull private final SpanName spanName;
+  @NonNull private final ServerStreamingCallable<RequestT, ResponseT> innerCallable;
 
   public TracedServerStreamingCallable(
-      @Nonnull ServerStreamingCallable<RequestT, ResponseT> innerCallable,
-      @Nonnull ApiTracerFactory tracerFactory,
-      @Nonnull SpanName spanName) {
+      @NonNull ServerStreamingCallable<RequestT, ResponseT> innerCallable,
+      @NonNull ApiTracerFactory tracerFactory,
+      @NonNull SpanName spanName) {
     this.tracerFactory = Preconditions.checkNotNull(tracerFactory, "tracerFactory can't be null");
     this.spanName = Preconditions.checkNotNull(spanName, "spanName can't be null");
     this.innerCallable = Preconditions.checkNotNull(innerCallable, "innerCallable can't be null");
diff --git a/gax-java/gax/src/test/java/com/google/api/gax/rpc/testing/FakeCallContext.java b/gax-java/gax/src/test/java/com/google/api/gax/rpc/testing/FakeCallContext.java
index 2eab2e1465..4f94f3d02f 100644
--- a/gax-java/gax/src/test/java/com/google/api/gax/rpc/testing/FakeCallContext.java
+++ b/gax-java/gax/src/test/java/com/google/api/gax/rpc/testing/FakeCallContext.java
@@ -50,7 +50,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import javax.annotation.Nonnull;
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 
 @InternalApi("for testing")
@@ -458,7 +458,7 @@ public <T> T getOption(Key<T> key) {
 
   /** {@inheritDoc} */
   @Override
-  @Nonnull
+  @NonNull
   public ApiTracer getTracer() {
     if (tracer == null) {
       return BaseApiTracer.getInstance();
@@ -468,7 +468,7 @@ public ApiTracer getTracer() {
 
   /** {@inheritDoc} */
   @Override
-  public ApiCallContext withTracer(@Nonnull ApiTracer tracer) {
+  public ApiCallContext withTracer(@NonNull ApiTracer tracer) {
     Preconditions.checkNotNull(tracer);
 
     return new FakeCallContext(