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fix: do not advertise 2024-11-05 from Streamable HTTP transport providers #1088

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fix: do not advertise 2024-11-05 from Streamable HTTP transport providers #1088

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14 changes: 14 additions & 0 deletions ...core/src/main/java/io/modelcontextprotocol/spec/McpStreamableServerTransportProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@

package io.modelcontextprotocol.spec;

import java.util.List;

import reactor.core.publisher.Mono;

/**
Expand Down Expand Up @@ -66,4 +68,16 @@ default void close() {
*/
Mono<Void> closeGracefully();

/**
* Streamable HTTP was introduced in protocol version {@code 2025-03-26}, so providers
* of this transport cannot serve {@code 2024-11-05} clients and must not advertise
* that version.
* @return the protocol versions supported by Streamable HTTP transport providers
*/
@Override
default List<String> protocolVersions() {
return List.of(ProtocolVersions.MCP_2025_03_26, ProtocolVersions.MCP_2025_06_18,
ProtocolVersions.MCP_2025_11_25);
}

}
81 changes: 81 additions & 0 deletions ...core/src/test/java/io/modelcontextprotocol/spec/ServerTransportProtocolVersionsTests.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,81 @@
/*
* Copyright 2024-2025 the original author or authors.
*/

package io.modelcontextprotocol.spec;

import java.util.List;

import io.modelcontextprotocol.server.McpStatelessServerHandler;
import org.junit.jupiter.api.Test;
import reactor.core.publisher.Mono;

import static org.assertj.core.api.Assertions.assertThat;

/**
* Verifies that each server transport abstraction advertises only the protocol versions
* it can actually serve.
*/
class ServerTransportProtocolVersionsTests {

private static final List<String> STREAMABLE_HTTP_VERSIONS = List.of(ProtocolVersions.MCP_2025_03_26,
ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);

private static final McpStreamableServerTransportProvider STREAMABLE_PROVIDER = new McpStreamableServerTransportProvider() {
@Override
public void setSessionFactory(McpStreamableServerSession.Factory sessionFactory) {
}

@Override
public Mono<Void> notifyClients(String method, Object params) {
return Mono.empty();
}

@Override
public Mono<Void> closeGracefully() {
return Mono.empty();
}
};

private static final McpStatelessServerTransport STATELESS_TRANSPORT = new McpStatelessServerTransport() {
@Override
public void setMcpHandler(McpStatelessServerHandler mcpHandler) {
}

@Override
public Mono<Void> closeGracefully() {
return Mono.empty();
}
};

@Test
void streamableProviderDoesNotAdvertiseVersionsPredatingStreamableHttp() {
assertThat(STREAMABLE_PROVIDER.protocolVersions()).doesNotContain(ProtocolVersions.MCP_2024_11_05)
.containsExactlyElementsOf(STREAMABLE_HTTP_VERSIONS);
}

@Test
void statelessTransportDoesNotAdvertiseVersionsPredatingStreamableHttp() {
assertThat(STATELESS_TRANSPORT.protocolVersions()).doesNotContain(ProtocolVersions.MCP_2024_11_05)
.containsExactlyElementsOf(STREAMABLE_HTTP_VERSIONS);
}

@Test
void transportsWithoutStreamableHttpConstraintKeepTheFullRange() {
McpServerTransportProviderBase base = new McpServerTransportProviderBase() {
@Override
public Mono<Void> notifyClients(String method, Object params) {
return Mono.empty();
}

@Override
public Mono<Void> closeGracefully() {
return Mono.empty();
}
};

assertThat(base.protocolVersions()).containsExactly(ProtocolVersions.MCP_2024_11_05,
ProtocolVersions.MCP_2025_03_26, ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);
}

}