diff --git a/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientSseClientTransport.java b/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientSseClientTransport.java
index 0f3511afb..7abc4d26c 100644
--- a/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientSseClientTransport.java
+++ b/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientSseClientTransport.java
@@ -23,6 +23,7 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 
 import io.modelcontextprotocol.client.transport.ResponseSubscribers.ResponseEvent;
+import io.modelcontextprotocol.spec.HttpHeaders;
 import io.modelcontextprotocol.spec.McpClientTransport;
 import io.modelcontextprotocol.spec.McpSchema;
 import io.modelcontextprotocol.spec.ProtocolVersions;
@@ -66,8 +67,6 @@ public class HttpClientSseClientTransport implements McpClientTransport {
 
 	private static final String MCP_PROTOCOL_VERSION = ProtocolVersions.MCP_2024_11_05;
 
-	private static final String MCP_PROTOCOL_VERSION_HEADER_NAME = "MCP-Protocol-Version";
-
 	private static final Logger logger = LoggerFactory.getLogger(HttpClientSseClientTransport.class);
 
 	/** SSE event type for JSON-RPC messages */
@@ -403,7 +402,7 @@ public Mono<Void> connect(Function<Mono<JSONRPCMessage>, Mono<JSONRPCMessage>> h
 				.uri(uri)
 				.header("Accept", "text/event-stream")
 				.header("Cache-Control", "no-cache")
-				.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
+				.header(HttpHeaders.PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
 				.GET();
 			return Mono.from(this.httpRequestCustomizer.customize(builder, "GET", uri, null));
 		}).flatMap(requestBuilder -> Mono.create(sink -> {
@@ -529,7 +528,7 @@ private Mono<HttpResponse<String>> sendHttpPost(final String endpoint, final Str
 		return Mono.defer(() -> {
 			var builder = this.requestBuilder.copy()
 				.uri(requestUri)
-				.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
+				.header(HttpHeaders.PROTOCOL_VERSION, MCP_PROTOCOL_VERSION)
 				.POST(HttpRequest.BodyPublishers.ofString(body));
 			return Mono.from(this.httpRequestCustomizer.customize(builder, "POST", requestUri, body));
 		}).flatMap(customizedBuilder -> {
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 93c28422a..fe59d0e3d 100644
--- a/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java
+++ b/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java
@@ -435,8 +435,10 @@ public Mono<Void> sendMessage(McpSchema.JSONRPCMessage sentMessage) {
 					})).onErrorMap(CompletionException.class, t -> t.getCause()).onErrorComplete().subscribe();
 
 			})).flatMap(responseEvent -> {
-				if (transportSession.markInitialized(
-						responseEvent.responseInfo().headers().firstValue("mcp-session-id").orElseGet(() -> null))) {
+				if (transportSession.markInitialized(responseEvent.responseInfo()
+					.headers()
+					.firstValue(HttpHeaders.MCP_SESSION_ID)
+					.orElseGet(() -> null))) {
 					// Once we have a session, we try to open an async stream for
 					// the server to send notifications and requests out-of-band.