diff --git a/mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/client/transport/WebClientStreamableHttpTransport.java b/mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/client/transport/WebClientStreamableHttpTransport.java
index 6d8e82f5..fd867efa 100644
--- a/mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/client/transport/WebClientStreamableHttpTransport.java
+++ b/mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/client/transport/WebClientStreamableHttpTransport.java
@@ -144,7 +144,7 @@ private DefaultMcpTransportSession createTransportSession() {
 				: webClient.delete()
 					.uri(this.endpoint)
 					.header(HttpHeaders.MCP_SESSION_ID, sessionId)
-					.header(HttpHeaders.PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
+					.header(HttpHeaders.MCP_PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
 					.retrieve()
 					.toBodilessEntity()
 					.onErrorComplete(e -> {
@@ -204,7 +204,7 @@ private Mono<Disposable> reconnect(McpTransportStream<Disposable> stream) {
 			Disposable connection = webClient.get()
 				.uri(this.endpoint)
 				.accept(MediaType.TEXT_EVENT_STREAM)
-				.header(HttpHeaders.PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
+				.header(HttpHeaders.MCP_PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
 				.headers(httpHeaders -> {
 					transportSession.sessionId().ifPresent(id -> httpHeaders.add(HttpHeaders.MCP_SESSION_ID, id));
 					if (stream != null) {
@@ -265,7 +265,7 @@ public Mono<Void> sendMessage(McpSchema.JSONRPCMessage message) {
 			Disposable connection = webClient.post()
 				.uri(this.endpoint)
 				.accept(MediaType.APPLICATION_JSON, MediaType.TEXT_EVENT_STREAM)
-				.header(HttpHeaders.PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
+				.header(HttpHeaders.MCP_PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
 				.headers(httpHeaders -> {
 					transportSession.sessionId().ifPresent(id -> httpHeaders.add(HttpHeaders.MCP_SESSION_ID, id));
 				})
diff --git a/mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/client/transport/WebFluxSseClientTransport.java b/mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/client/transport/WebFluxSseClientTransport.java
index 75caebef..013943b1 100644
--- a/mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/client/transport/WebFluxSseClientTransport.java
+++ b/mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/client/transport/WebFluxSseClientTransport.java
@@ -262,7 +262,7 @@ public Mono<Void> sendMessage(JSONRPCMessage message) {
 				return webClient.post()
 					.uri(messageEndpointUri)
 					.contentType(MediaType.APPLICATION_JSON)
-					.header(HttpHeaders.PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
+					.header(HttpHeaders.MCP_PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
 					.bodyValue(jsonText)
 					.retrieve()
 					.toBodilessEntity()
@@ -295,7 +295,7 @@ protected Flux<ServerSentEvent<String>> eventStream() {// @formatter:off
 			.get()
 			.uri(this.sseEndpoint)
 			.accept(MediaType.TEXT_EVENT_STREAM)
-			.header(HttpHeaders.PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
+			.header(HttpHeaders.MCP_PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
 			.retrieve()
 			.bodyToFlux(SSE_TYPE)
 			.retryWhen(Retry.from(retrySignal -> retrySignal.handle(inboundRetryHandler)));
diff --git a/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java b/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java
index 3cfa7359..cebdce4b 100644
--- a/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java
+++ b/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java
@@ -173,7 +173,7 @@ private Publisher<Void> createDelete(String sessionId) {
 				.uri(uri)
 				.header("Cache-Control", "no-cache")
 				.header(HttpHeaders.MCP_SESSION_ID, sessionId)
-				.header(HttpHeaders.PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
+				.header(HttpHeaders.MCP_PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
 				.DELETE();
 			return Mono.from(this.httpRequestCustomizer.customize(builder, "DELETE", uri, null));
 		}).flatMap(requestBuilder -> {
@@ -243,7 +243,7 @@ private Mono<Disposable> reconnect(McpTransportStream<Disposable> stream) {
 				var builder = requestBuilder.uri(uri)
 					.header("Accept", TEXT_EVENT_STREAM)
 					.header("Cache-Control", "no-cache")
-					.header(HttpHeaders.PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
+					.header(HttpHeaders.MCP_PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
 					.GET();
 				return Mono.from(this.httpRequestCustomizer.customize(builder, "GET", uri, null));
 			})
@@ -398,7 +398,7 @@ public Mono<Void> sendMessage(McpSchema.JSONRPCMessage sentMessage) {
 					.header("Accept", APPLICATION_JSON + ", " + TEXT_EVENT_STREAM)
 					.header("Content-Type", APPLICATION_JSON)
 					.header("Cache-Control", "no-cache")
-					.header(HttpHeaders.PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
+					.header(HttpHeaders.MCP_PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
 					.POST(HttpRequest.BodyPublishers.ofString(jsonBody));
 				return Mono.from(this.httpRequestCustomizer.customize(builder, "GET", uri, jsonBody));
 			}).flatMapMany(requestBuilder -> Flux.<ResponseEvent>create(responseEventSink -> {
diff --git a/mcp/src/main/java/io/modelcontextprotocol/spec/HttpHeaders.java b/mcp/src/main/java/io/modelcontextprotocol/spec/HttpHeaders.java
index 65b80957..e2bbadb7 100644
--- a/mcp/src/main/java/io/modelcontextprotocol/spec/HttpHeaders.java
+++ b/mcp/src/main/java/io/modelcontextprotocol/spec/HttpHeaders.java
@@ -8,6 +8,7 @@
  * Names of HTTP headers in use by MCP HTTP transports.
  *
  * @author Dariusz Jędrzejczyk
+ * @author Yanming Zhou
  */
 public interface HttpHeaders {
 
@@ -16,6 +17,11 @@ public interface HttpHeaders {
 	 */
 	String MCP_SESSION_ID = "mcp-session-id";
 
+	/**
+	 * Identifies the MCP protocol version.
+	 */
+	String MCP_PROTOCOL_VERSION = "MCP-Protocol-Version";
+
 	/**
 	 * Identifies events within an SSE Stream.
 	 */
@@ -23,7 +29,9 @@ public interface HttpHeaders {
 
 	/**
 	 * Identifies the MCP protocol version.
+	 * @deprecated use {@link MCP_PROTOCOL_VERSION} instead
 	 */
-	String PROTOCOL_VERSION = "MCP-Protocol-Version";
+	@Deprecated(forRemoval = true)
+	String PROTOCOL_VERSION = MCP_PROTOCOL_VERSION;
 
 }