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feat: implement MCP protocol version header support #404

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26 changes: 20 additions & 6 deletions .../main/java/io/modelcontextprotocol/client/transport/WebClientStreamableHttpTransport.java
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,10 @@ public class WebClientStreamableHttpTransport implements McpClientTransport {

private static final Logger logger = LoggerFactory.getLogger(WebClientStreamableHttpTransport.class);

private static final String MCP_PROTOCOL_VERSION = "2025-06-18";

private static final String MCP_PROTOCOL_VERSION_HEADER_NAME = "MCP-Protocol-Version";

private static final String DEFAULT_ENDPOINT = "/mcp";

/**
Expand Down Expand Up @@ -127,12 +131,20 @@ public Mono<Void> connect(Function<Mono<McpSchema.JSONRPCMessage>, Mono<McpSchem

private DefaultMcpTransportSession createTransportSession() {
Function<String, Publisher<Void>> onClose = sessionId -> sessionId == null ? Mono.empty()
: webClient.delete().uri(this.endpoint).headers(httpHeaders -> {
httpHeaders.add("mcp-session-id", sessionId);
}).retrieve().toBodilessEntity().onErrorComplete(e -> {
logger.warn("Got error when closing transport", e);
return true;
}).then();
: webClient.delete()
.uri(this.endpoint)
.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
.headers(httpHeaders -> {
httpHeaders.add("mcp-session-id", sessionId);
httpHeaders.add(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION);
})
.retrieve()
.toBodilessEntity()
.onErrorComplete(e -> {
logger.warn("Got error when closing transport", e);
return true;
})
.then();
return new DefaultMcpTransportSession(onClose);
}

Expand Down Expand Up @@ -185,6 +197,7 @@ private Mono<Disposable> reconnect(McpTransportStream<Disposable> stream) {
Disposable connection = webClient.get()
.uri(this.endpoint)
.accept(MediaType.TEXT_EVENT_STREAM)
.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
.headers(httpHeaders -> {
transportSession.sessionId().ifPresent(id -> httpHeaders.add("mcp-session-id", id));
if (stream != null) {
Expand Down Expand Up @@ -245,6 +258,7 @@ public Mono<Void> sendMessage(McpSchema.JSONRPCMessage message) {
Disposable connection = webClient.post()
.uri(this.endpoint)
.accept(MediaType.TEXT_EVENT_STREAM, MediaType.APPLICATION_JSON)
.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
.headers(httpHeaders -> {
transportSession.sessionId().ifPresent(id -> httpHeaders.add("mcp-session-id", id));
})
Expand Down
6 changes: 6 additions & 0 deletions ...lux/src/main/java/io/modelcontextprotocol/client/transport/WebFluxSseClientTransport.java
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,10 @@ public class WebFluxSseClientTransport implements McpClientTransport {

private static final Logger logger = LoggerFactory.getLogger(WebFluxSseClientTransport.class);

private static final String MCP_PROTOCOL_VERSION = "2024-11-05";

private static final String MCP_PROTOCOL_VERSION_HEADER_NAME = "MCP-Protocol-Version";

/**
* Event type for JSON-RPC messages received through the SSE connection. The server
* sends messages with this event type to transmit JSON-RPC protocol data.
Expand Down Expand Up @@ -249,6 +253,7 @@ public Mono<Void> sendMessage(JSONRPCMessage message) {
return webClient.post()
.uri(messageEndpointUri)
.contentType(MediaType.APPLICATION_JSON)
.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
.bodyValue(jsonText)
.retrieve()
.toBodilessEntity()
Expand Down Expand Up @@ -281,6 +286,7 @@ protected Flux<ServerSentEvent<String>> eventStream() {// @formatter:off
.get()
.uri(this.sseEndpoint)
.accept(MediaType.TEXT_EVENT_STREAM)
.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
.retrieve()
.bodyToFlux(SSE_TYPE)
.retryWhen(Retry.from(retrySignal -> retrySignal.handle(inboundRetryHandler)));
Expand Down
6 changes: 6 additions & 0 deletions mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientSseClientTransport.java
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,10 @@
*/
public class HttpClientSseClientTransport implements McpClientTransport {

private static final String MCP_PROTOCOL_VERSION = "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 */
Expand Down Expand Up @@ -330,6 +334,7 @@ public Mono<Void> connect(Function<Mono<JSONRPCMessage>, Mono<JSONRPCMessage>> h
.uri(Utils.resolveUri(this.baseUri, this.sseEndpoint))
.header("Accept", "text/event-stream")
.header("Cache-Control", "no-cache")
.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
.GET()
.build();

Expand Down Expand Up @@ -457,6 +462,7 @@ private Mono<HttpResponse<String>> sendHttpPost(final String endpoint, final Str
final URI requestUri = Utils.resolveUri(baseUri, endpoint);
final HttpRequest request = this.requestBuilder.copy()
.uri(requestUri)
.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
.POST(HttpRequest.BodyPublishers.ofString(body))
.build();

Expand Down
7 changes: 7 additions & 0 deletions ...main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java
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Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,10 @@ public class HttpClientStreamableHttpTransport implements McpClientTransport {

private static final Logger logger = LoggerFactory.getLogger(HttpClientStreamableHttpTransport.class);

private static final String MCP_PROTOCOL_VERSION = "2025-06-18";

private static final String MCP_PROTOCOL_VERSION_HEADER_NAME = "MCP-Protocol-Version";

private static final String DEFAULT_ENDPOINT = "/mcp";

/**
Expand Down Expand Up @@ -158,6 +162,7 @@ private Publisher<Void> createDelete(String sessionId) {
.uri(Utils.resolveUri(this.baseUri, this.endpoint))
.header("Cache-Control", "no-cache")
.header("mcp-session-id", sessionId)
.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
.DELETE()
.build();

Expand Down Expand Up @@ -222,6 +227,7 @@ private Mono<Disposable> reconnect(McpTransportStream<Disposable> stream) {
HttpRequest request = requestBuilder.uri(Utils.resolveUri(this.baseUri, this.endpoint))
.header("Accept", TEXT_EVENT_STREAM)
.header("Cache-Control", "no-cache")
.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
.GET()
.build();

Expand Down Expand Up @@ -361,6 +367,7 @@ public Mono<Void> sendMessage(McpSchema.JSONRPCMessage sendMessage) {
.header("Accept", TEXT_EVENT_STREAM + ", " + APPLICATION_JSON)
.header("Content-Type", APPLICATION_JSON)
.header("Cache-Control", "no-cache")
.header(MCP_PROTOCOL_VERSION_HEADER_NAME, MCP_PROTOCOL_VERSION)
.POST(HttpRequest.BodyPublishers.ofString(jsonBody))
.build();

Expand Down
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