diff --git a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
index 55f41cf9457..92b16f85e49 100644
--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
@@ -1160,7 +1160,7 @@ public record ChatCompletionRequest(// @formatter:off
 			@JsonProperty("verbosity") String verbosity,
 			@JsonProperty("prompt_cache_key") String promptCacheKey,
 			@JsonProperty("safety_identifier") String safetyIdentifier,
-			Map<String, Object> extraBody) {
+			@JsonProperty("extra_body") Map<String, Object> extraBody) {
 
 		/**
 		 * Compact constructor that ensures extraBody is initialized as a mutable HashMap
diff --git a/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/ExtraBodySerializationTest.java b/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/ExtraBodySerializationTest.java
index 28e9113e27d..9282bebe7fc 100644
--- a/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/ExtraBodySerializationTest.java
+++ b/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/ExtraBodySerializationTest.java
@@ -22,6 +22,8 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.ai.model.ModelOptionsUtils;
+import org.springframework.ai.openai.OpenAiChatOptions;
 import org.springframework.ai.openai.api.OpenAiApi.ChatCompletionRequest;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -208,4 +210,25 @@ void testDeserializationWithComplexExtraFields() throws Exception {
 		assertThat(request.extraBody().get("stop_token_ids")).isInstanceOf(List.class);
 	}
 
+	@Test
+	void testMergeWithExtraBody() throws Exception {
+		// Arrange: Create OpenAiChatOptions with extraBody
+		OpenAiChatOptions requestOptions = OpenAiChatOptions.builder()
+				.model("test-model")
+				.extraBody(Map.of("enable_thinking", true, "max_depth", 10))
+				.build();
+
+		// Create empty ChatCompletionRequest
+		ChatCompletionRequest request = new ChatCompletionRequest(null, null);
+		
+		// Act: Merge options into request
+		request = ModelOptionsUtils.merge(requestOptions, request, ChatCompletionRequest.class);
+
+		// Assert: Verify extraBody was successfully merged
+		assertThat(request.extraBody()).isNotNull();
+		assertThat(request.extraBody()).containsEntry("enable_thinking", true);
+		assertThat(request.extraBody()).containsEntry("max_depth", 10);
+		assertThat(request.model()).isEqualTo("test-model");
+	}
+
 }