diff --git a/core/src/main/java/com/google/adk/codeexecutors/CodeExecutionUtils.java b/core/src/main/java/com/google/adk/codeexecutors/CodeExecutionUtils.java
index b9afdcaff..a4d3771c3 100644
--- a/core/src/main/java/com/google/adk/codeexecutors/CodeExecutionUtils.java
+++ b/core/src/main/java/com/google/adk/codeexecutors/CodeExecutionUtils.java
@@ -34,6 +34,7 @@
 import java.util.Optional;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+import org.jspecify.annotations.Nullable;
 
 /** Utility functions for code execution. */
 public final class CodeExecutionUtils {
@@ -237,8 +238,7 @@ public abstract static class CodeExecutionInput extends JsonBaseModel {
 
     public static Builder builder() {
       return new AutoValue_CodeExecutionUtils_CodeExecutionInput.Builder()
-          .inputFiles(ImmutableList.of())
-          .executionId(Optional.empty());
+          .inputFiles(ImmutableList.of());
     }
 
     /** Builder for {@link CodeExecutionInput}. */
@@ -248,7 +248,7 @@ public abstract static class Builder {
 
       public abstract Builder inputFiles(List<File> inputFiles);
 
-      public abstract Builder executionId(Optional<String> executionId);
+      public abstract Builder executionId(@Nullable String executionId);
 
       public abstract CodeExecutionInput build();
     }
diff --git a/core/src/main/java/com/google/adk/flows/llmflows/CodeExecution.java b/core/src/main/java/com/google/adk/flows/llmflows/CodeExecution.java
index f2cbe967e..d76cd1a04 100644
--- a/core/src/main/java/com/google/adk/flows/llmflows/CodeExecution.java
+++ b/core/src/main/java/com/google/adk/flows/llmflows/CodeExecution.java
@@ -240,7 +240,8 @@ private static Flowable<Event> runPreProcessor(
                                     .code(codeStr)
                                     .inputFiles(ImmutableList.of(file))
                                     .executionId(
-                                        getOrSetExecutionId(invocationContext, codeExecutorContext))
+                                        getOrSetExecutionId(invocationContext, codeExecutorContext)
+                                            .orElse(null))
                                     .build());
 
                         codeExecutorContext.updateCodeExecutionResult(
@@ -320,7 +321,9 @@ private static Flowable<Event> runPostProcessor(
                       CodeExecutionInput.builder()
                           .code(codeStr)
                           .inputFiles(codeExecutorContext.getInputFiles())
-                          .executionId(getOrSetExecutionId(invocationContext, codeExecutorContext))
+                          .executionId(
+                              getOrSetExecutionId(invocationContext, codeExecutorContext)
+                                  .orElse(null))
                           .build());
               codeExecutorContext.updateCodeExecutionResult(
                   invocationContext.invocationId(),