diff --git a/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java b/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
index de3460d31b7..b43069e9a79 100644
--- a/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
+++ b/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
@@ -16,29 +16,30 @@
 
 package org.springframework.ai.openai.api;
 
-import java.io.IOException;
-import java.util.List;
-import java.util.Map;
-import java.util.function.Consumer;
-
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonInclude.Include;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.ObjectMapper;
-import reactor.core.publisher.Flux;
-import reactor.core.publisher.Mono;
-
 import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.http.client.ClientHttpResponse;
+import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.web.client.ResponseErrorHandler;
 import org.springframework.web.client.RestClient;
 import org.springframework.web.reactive.function.client.WebClient;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
 
 // @formatter:off
 /**
@@ -51,7 +52,7 @@ public class OpenAiApi {
 
 	private static final String DEFAULT_BASE_URL = "https://api.openai.com";
 	private static final String DEFAULT_EMBEDDING_MODEL = "text-embedding-ada-002";
-	private static final String SSE_DONE = "[DONE]";
+	private static final Predicate<String> SSE_DONE_PREDICATE = "[DONE]"::equals;
 
 	private final RestClient restClient;
 	private final WebClient webClient;
@@ -74,8 +75,8 @@ public OpenAiApi(String openAiToken) {
 	 * @param restClientBuilder RestClient builder.
 	 */
 	public OpenAiApi(String baseUrl, String openAiToken, RestClient.Builder restClientBuilder) {
-
-		this.objectMapper = new ObjectMapper();
+		// Use the same ObjectMapper for WebClient's response as the one used in RestClient.
+		this.objectMapper = Jackson2ObjectMapperBuilder.json().build();
 
 		Consumer<HttpHeaders> jsonContentHeaders = headers -> {
 			headers.setBearerAuth(openAiToken);
@@ -533,7 +534,15 @@ public record ChatCompletionChunk(
 		public record ChunkChoice(
 				@JsonProperty("finish_reason") ChatCompletionFinishReason finishReason,
 				@JsonProperty("index") Integer index,
-				@JsonProperty("delta") ChatCompletionMessage delta) {
+				@JsonProperty("delta") Delta delta
+		) {
+			// The delta used in ChatCompletionChunk is not identical to ChatCompletion's ChatCompletionMessage, so a Delta record needs to be defined separately.
+			public record Delta(
+
+					@JsonProperty("role") ChatCompletionMessage.Role role,
+
+					@JsonProperty("content") String content) {
+			}
 		}
 	}
 
@@ -571,10 +580,10 @@ public Flux<ChatCompletionChunk> chatCompletionStream(ChatCompletionRequest chat
 				.body(Mono.just(chatRequest), ChatCompletionRequest.class)
 				.retrieve()
 				.bodyToFlux(String.class)
-				// cancels the flux stream after the SSE_DONE is received.
-				.takeUntil(content -> content.contains(SSE_DONE))
-				// filters out the SSE_DONE message.
-				.filter(content -> !content.contains(SSE_DONE))
+				// cancels the flux stream after the "[DONE]" is received.
+				.takeUntil(SSE_DONE_PREDICATE)
+				// filters out the "[DONE]" message.
+				.filter(SSE_DONE_PREDICATE.negate())
 				.map(content -> parseJson(content, ChatCompletionChunk.class));
 	}