modelcontextprotocol/java-sdk
Watch
1
0
Fork
You've already forked java-sdk
 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Basic version negotiation capabilities

Browse source 
- We do not support full version negotiation, but this commit allows the
  client to the send the correct version to match that of the server.
- There is one limitation: the GET /mcp request happens too early,
  before we have deserialized the initialization response, so we do not
  know the negotiated version yet. This request will have the client
  latest version as Mcp-Protocol-Version value.

Signed-off-by: Daniel Garnier-Moiroux <git@garnier.wf>
This commit is contained in:
Daniel Garnier-Moiroux 2025-11-20 15:50:46 +01:00 • committed by Daniel Garnier-Moiroux
commit e6045f7287
4 changed files with 53 additions and 27 deletions
Download patch file Download diff file Expand all files Collapse all files

6
mcp-core/src/main/java/io/modelcontextprotocol/client/LifecycleInitializer.java
View file

@ -287,7 +287,9 @@ class LifecycleInitializer {
this.initializationRef.compareAndSet(newInit, null);
return Mono.error(new RuntimeException("Client failed to initialize " + actionName, ex));
})
.flatMap(operation);
.flatMap(res -> operation.apply(res)
.contextWrite(c -> c.put(McpAsyncClient.NEGOTIATED_PROTOCOL_VERSION,
res.initializeResult().protocolVersion())));
});
}
@ -319,6 +321,8 @@ class LifecycleInitializer {
}
return mcpClientSession.sendNotification(McpSchema.METHOD_NOTIFICATION_INITIALIZED, null)
.contextWrite(
c -> c.put(McpAsyncClient.NEGOTIATED_PROTOCOL_VERSION, initializeResult.protocolVersion()))
.thenReturn(initializeResult);
}).flatMap(initializeResult -> {
initialization.cacheResult(initializeResult);

2
mcp-core/src/main/java/io/modelcontextprotocol/client/McpAsyncClient.java
View file

@ -106,6 +106,8 @@ public class McpAsyncClient {
public static final TypeRef<McpSchema.ProgressNotification> PROGRESS_NOTIFICATION_TYPE_REF = new TypeRef<>() {
};
public static final String NEGOTIATED_PROTOCOL_VERSION = "io.modelcontextprotocol.client.negotiated-protocol-version";
/**
* Client capabilities.
*/

13
mcp-core/src/main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java
View file

@ -20,6 +20,7 @@ import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Consumer;
import java.util.function.Function;
import io.modelcontextprotocol.client.McpAsyncClient;
import io.modelcontextprotocol.client.transport.ResponseSubscribers.ResponseEvent;
import io.modelcontextprotocol.client.transport.customizer.McpAsyncHttpClientRequestCustomizer;
import io.modelcontextprotocol.client.transport.customizer.McpSyncHttpClientRequestCustomizer;
@ -193,7 +194,9 @@ public class HttpClientStreamableHttpTransport implements McpClientTransport {
.uri(uri)
.header("Cache-Control", "no-cache")
.header(HttpHeaders.MCP_SESSION_ID, sessionId)
.header(HttpHeaders.PROTOCOL_VERSION, this.latestSupportedProtocolVersion)
.header(HttpHeaders.PROTOCOL_VERSION,
ctx.getOrDefault(McpAsyncClient.NEGOTIATED_PROTOCOL_VERSION,
this.latestSupportedProtocolVersion))
.DELETE();
var transportContext = ctx.getOrDefault(McpTransportContext.KEY, McpTransportContext.EMPTY);
return Mono.from(this.httpRequestCustomizer.customize(builder, "DELETE", uri, null, transportContext));
@ -264,7 +267,9 @@ public class HttpClientStreamableHttpTransport implements McpClientTransport {
var builder = requestBuilder.uri(uri)
.header(HttpHeaders.ACCEPT, TEXT_EVENT_STREAM)
.header("Cache-Control", "no-cache")
.header(HttpHeaders.PROTOCOL_VERSION, this.latestSupportedProtocolVersion)
.header(HttpHeaders.PROTOCOL_VERSION,
connectionCtx.getOrDefault(McpAsyncClient.NEGOTIATED_PROTOCOL_VERSION,
this.latestSupportedProtocolVersion))
.GET();
var transportContext = connectionCtx.getOrDefault(McpTransportContext.KEY, McpTransportContext.EMPTY);
return Mono.from(this.httpRequestCustomizer.customize(builder, "GET", uri, null, transportContext));
@ -439,7 +444,9 @@ public class HttpClientStreamableHttpTransport implements McpClientTransport {
.header(HttpHeaders.ACCEPT, APPLICATION_JSON + ", " + TEXT_EVENT_STREAM)
.header(HttpHeaders.CONTENT_TYPE, APPLICATION_JSON)
.header(HttpHeaders.CACHE_CONTROL, "no-cache")
.header(HttpHeaders.PROTOCOL_VERSION, this.latestSupportedProtocolVersion)
.header(HttpHeaders.PROTOCOL_VERSION,
ctx.getOrDefault(McpAsyncClient.NEGOTIATED_PROTOCOL_VERSION,
this.latestSupportedProtocolVersion))
.POST(HttpRequest.BodyPublishers.ofString(jsonBody));
var transportContext = ctx.getOrDefault(McpTransportContext.KEY, McpTransportContext.EMPTY);
return Mono

4
mcp-core/src/main/java/io/modelcontextprotocol/spec/McpTransportSession.java
View file

@ -4,10 +4,10 @@
package io.modelcontextprotocol.spec;
import org.reactivestreams.Publisher;
import java.util.Optional;
import org.reactivestreams.Publisher;
/**
* An abstraction of the session as perceived from the MCP transport layer. Not to be
* confused with the {@link McpSession} type that operates at the level of the JSON-RPC