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 1f99cf4a2..be0504dd4 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
@@ -303,7 +303,7 @@ private static Flowable<Event> runPostProcessor(
     }
     String codeStr = codeStrOptional.get();
     responseContent = responseContentBuilder.build();
-    llmResponseBuilder.content(Optional.empty());
+    llmResponseBuilder.content((Content) null);
 
     Event codeEvent =
         Event.builder()
diff --git a/core/src/main/java/com/google/adk/models/GeminiLlmConnection.java b/core/src/main/java/com/google/adk/models/GeminiLlmConnection.java
index 2e1229d0b..7585d3a7a 100644
--- a/core/src/main/java/com/google/adk/models/GeminiLlmConnection.java
+++ b/core/src/main/java/com/google/adk/models/GeminiLlmConnection.java
@@ -191,7 +191,7 @@ private static LlmResponse createServerContentResponse(LiveServerContent serverC
     return builder
         .partial(serverContent.turnComplete().map(completed -> !completed).orElse(false))
         .turnComplete(serverContent.turnComplete().orElse(false))
-        .interrupted(serverContent.interrupted())
+        .interrupted(serverContent.interrupted().orElse(null))
         .build();
   }
 
diff --git a/core/src/main/java/com/google/adk/models/LlmResponse.java b/core/src/main/java/com/google/adk/models/LlmResponse.java
index 78791acfa..1ca381e23 100644
--- a/core/src/main/java/com/google/adk/models/LlmResponse.java
+++ b/core/src/main/java/com/google/adk/models/LlmResponse.java
@@ -128,74 +128,51 @@ static LlmResponse.Builder jacksonBuilder() {
     }
 
     @JsonProperty("content")
-    public abstract Builder content(Content content);
-
-    public abstract Builder content(Optional<Content> content);
+    public abstract Builder content(@Nullable Content content);
 
     @JsonProperty("interrupted")
     public abstract Builder interrupted(@Nullable Boolean interrupted);
 
-    public abstract Builder interrupted(Optional<Boolean> interrupted);
-
     @JsonProperty("groundingMetadata")
     public abstract Builder groundingMetadata(@Nullable GroundingMetadata groundingMetadata);
 
-    public abstract Builder groundingMetadata(Optional<GroundingMetadata> groundingMetadata);
-
     @JsonProperty("customMetadata")
     public abstract Builder customMetadata(@Nullable List<CustomMetadata> customMetadata);
 
     @JsonProperty("partial")
     public abstract Builder partial(@Nullable Boolean partial);
 
-    public abstract Builder partial(Optional<Boolean> partial);
-
     @JsonProperty("turnComplete")
     public abstract Builder turnComplete(@Nullable Boolean turnComplete);
 
-    public abstract Builder turnComplete(Optional<Boolean> turnComplete);
-
     @JsonProperty("errorCode")
     public abstract Builder errorCode(@Nullable FinishReason errorCode);
 
-    public abstract Builder errorCode(Optional<FinishReason> errorCode);
-
     @JsonProperty("finishReason")
     public abstract Builder finishReason(@Nullable FinishReason finishReason);
 
-    public abstract Builder finishReason(Optional<FinishReason> finishReason);
-
     @JsonProperty("avgLogprobs")
     public abstract Builder avgLogprobs(@Nullable Double avgLogprobs);
 
-    public abstract Builder avgLogprobs(Optional<Double> avgLogprobs);
-
     @JsonProperty("errorMessage")
     public abstract Builder errorMessage(@Nullable String errorMessage);
 
-    public abstract Builder errorMessage(Optional<String> errorMessage);
-
     @JsonProperty("usageMetadata")
     public abstract Builder usageMetadata(
         @Nullable GenerateContentResponseUsageMetadata usageMetadata);
 
-    public abstract Builder usageMetadata(
-        Optional<GenerateContentResponseUsageMetadata> usageMetadata);
-
     @JsonProperty("modelVersion")
     public abstract Builder modelVersion(@Nullable String modelVersion);
 
-    public abstract Builder modelVersion(Optional<String> modelVersion);
-
     @CanIgnoreReturnValue
     public final Builder response(GenerateContentResponse response) {
       Optional<List<Candidate>> candidatesOpt = response.candidates();
       if (candidatesOpt.isPresent() && !candidatesOpt.get().isEmpty()) {
         Candidate candidate = candidatesOpt.get().get(0);
-        this.finishReason(candidate.finishReason());
+        this.finishReason(candidate.finishReason().orElse(null));
         if (candidate.content().isPresent()) {
           this.content(candidate.content().get());
-          this.groundingMetadata(candidate.groundingMetadata());
+          this.groundingMetadata(candidate.groundingMetadata().orElse(null));
         } else {
           candidate.finishReason().ifPresent(this::errorCode);
           candidate.finishMessage().ifPresent(this::errorMessage);
@@ -214,8 +191,8 @@ public final Builder response(GenerateContentResponse response) {
           this.errorMessage("Unknown error.");
         }
       }
-      this.usageMetadata(response.usageMetadata());
-      this.modelVersion(response.modelVersion());
+      this.usageMetadata(response.usageMetadata().orElse(null));
+      this.modelVersion(response.modelVersion().orElse(null));
       return this;
     }
 
diff --git a/core/src/test/java/com/google/adk/models/LlmResponseTest.java b/core/src/test/java/com/google/adk/models/LlmResponseTest.java
index 65e00413f..646b89602 100644
--- a/core/src/test/java/com/google/adk/models/LlmResponseTest.java
+++ b/core/src/test/java/com/google/adk/models/LlmResponseTest.java
@@ -28,7 +28,6 @@
 import com.google.genai.types.FunctionCall;
 import com.google.genai.types.GenerateContentResponseUsageMetadata;
 import com.google.genai.types.Part;
-import java.util.Optional;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -74,8 +73,8 @@ public void testSerializationAndDeserialization_allFieldsPresent()
             .partial(true)
             .turnComplete(false)
             .errorCode(new FinishReason("ERR_123"))
-            .errorMessage(Optional.of("An error occurred."))
-            .interrupted(Optional.of(true))
+            .errorMessage("An error occurred.")
+            .interrupted(true)
             .usageMetadata(usageMetadata)
             .build();
 
@@ -113,16 +112,7 @@ public void testSerializationAndDeserialization_optionalFieldsEmpty()
       throws JsonProcessingException {
     Content sampleContent = createSampleFunctionCallContent("tool_abc");
     LlmResponse originalResponse =
-        LlmResponse.builder()
-            .content(sampleContent)
-            .groundingMetadata(Optional.empty())
-            .partial(Optional.empty())
-            .turnComplete(false)
-            .errorCode(Optional.empty())
-            .errorMessage(Optional.empty())
-            .interrupted(Optional.empty())
-            .usageMetadata(Optional.empty())
-            .build();
+        LlmResponse.builder().content(sampleContent).turnComplete(false).build();
 
     String json = originalResponse.toJson();
     assertThat(json).isNotNull();