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feat: broadcast 2025-11-25 as latest supported client version #758

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abc48b4
feat: broadcast 2025-11-25 as latest supported client version
LucaButBoring Jan 22, 2026
4517a23
fix: ignore empty SSE events
LucaButBoring Jan 23, 2026
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28 changes: 24 additions & 4 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 @@ -295,12 +295,23 @@ private Mono<Disposable> reconnect(McpTransportStream<Disposable> stream) {
if (statusCode >= 200 && statusCode < 300) {

if (MESSAGE_EVENT_TYPE.equals(responseEvent.sseEvent().event())) {
String data = responseEvent.sseEvent().data();
// Per 2025-11-25 spec (SEP-1699), servers may
// send SSE events
// with empty data to prime the client for
// reconnection.
// Skip these events as they contain no JSON-RPC
// message.
if (data == null || data.isBlank()) {
logger.debug("Skipping SSE event with empty data (stream primer)");
return Flux.empty();
}
try {
// We don't support batching ATM and probably
// won't since the next version considers
// removing it.
McpSchema.JSONRPCMessage message = McpSchema.deserializeJsonRpcMessage(
this.jsonMapper, responseEvent.sseEvent().data());
McpSchema.JSONRPCMessage message = McpSchema
.deserializeJsonRpcMessage(this.jsonMapper, data);

Tuple2<Optional<String>, Iterable<McpSchema.JSONRPCMessage>> idWithMessages = Tuples
.of(Optional.ofNullable(responseEvent.sseEvent().id()),
Expand Down Expand Up @@ -503,13 +514,22 @@ public Mono<Void> sendMessage(McpSchema.JSONRPCMessage sentMessage) {
else if (contentType.contains(TEXT_EVENT_STREAM)) {
return Flux.just(((ResponseSubscribers.SseResponseEvent) responseEvent).sseEvent())
.flatMap(sseEvent -> {
String data = sseEvent.data();
// Per 2025-11-25 spec (SEP-1699), servers may send SSE
// events
// with empty data to prime the client for reconnection.
// Skip these events as they contain no JSON-RPC message.
if (data == null || data.isBlank()) {
logger.debug("Skipping SSE event with empty data (stream primer)");
return Flux.empty();
}
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@He-Pin He-Pin Jan 23, 2026

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Nice fix

try {
// We don't support batching ATM and probably
// won't
// since the
// next version considers removing it.
McpSchema.JSONRPCMessage message = McpSchema
.deserializeJsonRpcMessage(this.jsonMapper, sseEvent.data());
.deserializeJsonRpcMessage(this.jsonMapper, data);

Tuple2<Optional<String>, Iterable<McpSchema.JSONRPCMessage>> idWithMessages = Tuples
.of(Optional.ofNullable(sseEvent.id()), List.of(message));
Expand Down Expand Up @@ -641,7 +661,7 @@ public static class Builder {
private Duration connectTimeout = Duration.ofSeconds(10);

private List<String> supportedProtocolVersions = List.of(ProtocolVersions.MCP_2024_11_05,
ProtocolVersions.MCP_2025_03_26, ProtocolVersions.MCP_2025_06_18);
ProtocolVersions.MCP_2025_03_26, ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);

/**
* Creates a new builder with the specified base URI.
Expand Down
2 changes: 1 addition & 1 deletion ...o/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java
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Expand Up @@ -157,7 +157,7 @@ private HttpServletStreamableServerTransportProvider(McpJsonMapper jsonMapper, S
@Override
public List<String> protocolVersions() {
return List.of(ProtocolVersions.MCP_2024_11_05, ProtocolVersions.MCP_2025_03_26,
ProtocolVersions.MCP_2025_06_18);
ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);
}

@Override
Expand Down
2 changes: 1 addition & 1 deletion mcp-core/src/main/java/io/modelcontextprotocol/spec/McpSchema.java
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,7 @@ private McpSchema() {
}

@Deprecated
public static final String LATEST_PROTOCOL_VERSION = ProtocolVersions.MCP_2025_06_18;
public static final String LATEST_PROTOCOL_VERSION = ProtocolVersions.MCP_2025_11_25;

public static final String JSONRPC_VERSION = "2.0";

Expand Down
3 changes: 2 additions & 1 deletion mcp-core/src/main/java/io/modelcontextprotocol/spec/McpStatelessServerTransport.java
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Expand Up @@ -29,7 +29,8 @@ default void close() {
Mono<Void> closeGracefully();

default List<String> protocolVersions() {
return List.of(ProtocolVersions.MCP_2025_03_26, ProtocolVersions.MCP_2025_06_18);
return List.of(ProtocolVersions.MCP_2025_03_26, ProtocolVersions.MCP_2025_06_18,
ProtocolVersions.MCP_2025_11_25);
}

}
4 changes: 2 additions & 2 deletions .../java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransportTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,7 @@ void testRequestCustomizer() throws URISyntaxException {

// Verify the customizer was called
verify(mockRequestCustomizer, atLeastOnce()).customize(any(), eq("POST"), eq(uri), eq(
"{\"jsonrpc\":\"2.0\",\"method\":\"initialize\",\"id\":\"test-id\",\"params\":{\"protocolVersion\":\"2025-06-18\",\"capabilities\":{\"roots\":{\"listChanged\":true}},\"clientInfo\":{\"name\":\"MCP Client\",\"version\":\"0.3.1\"}}}"),
"{\"jsonrpc\":\"2.0\",\"method\":\"initialize\",\"id\":\"test-id\",\"params\":{\"protocolVersion\":\"2025-11-25\",\"capabilities\":{\"roots\":{\"listChanged\":true}},\"clientInfo\":{\"name\":\"MCP Client\",\"version\":\"0.3.1\"}}}"),
eq(context));
});
}
Expand Down Expand Up @@ -120,7 +120,7 @@ void testAsyncRequestCustomizer() throws URISyntaxException {

// Verify the customizer was called
verify(mockRequestCustomizer, atLeastOnce()).customize(any(), eq("POST"), eq(uri), eq(
"{\"jsonrpc\":\"2.0\",\"method\":\"initialize\",\"id\":\"test-id\",\"params\":{\"protocolVersion\":\"2025-06-18\",\"capabilities\":{\"roots\":{\"listChanged\":true}},\"clientInfo\":{\"name\":\"MCP Client\",\"version\":\"0.3.1\"}}}"),
"{\"jsonrpc\":\"2.0\",\"method\":\"initialize\",\"id\":\"test-id\",\"params\":{\"protocolVersion\":\"2025-11-25\",\"capabilities\":{\"roots\":{\"listChanged\":true}},\"clientInfo\":{\"name\":\"MCP Client\",\"version\":\"0.3.1\"}}}"),
eq(context));
});
}
Expand Down
10 changes: 5 additions & 5 deletions ...delcontextprotocol/common/HttpClientStreamableHttpVersionNegotiationIntegrationTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -77,14 +77,14 @@ void usesLatestVersion() {
.hasSize(3)
.map(McpTestRequestRecordingServletFilter.Call::headers)
.allSatisfy(headers -> assertThat(headers).containsEntry("mcp-protocol-version",
ProtocolVersions.MCP_2025_06_18));
ProtocolVersions.MCP_2025_11_25));

assertThat(response).isNotNull();
assertThat(response.content()).hasSize(1)
.first()
.extracting(McpSchema.TextContent.class::cast)
.extracting(McpSchema.TextContent::text)
.isEqualTo(ProtocolVersions.MCP_2025_06_18);
.isEqualTo(ProtocolVersions.MCP_2025_11_25);
mcpServer.close();
}

Expand All @@ -93,7 +93,7 @@ void usesServerSupportedVersion() {
startTomcat();

var transport = HttpClientStreamableHttpTransport.builder("http://localhost:" + PORT)
.supportedProtocolVersions(List.of(ProtocolVersions.MCP_2025_06_18, "2263-03-18"))
.supportedProtocolVersions(List.of(ProtocolVersions.MCP_2025_11_25, "2263-03-18"))
.build();
var client = McpClient.sync(transport).build();

Expand All @@ -108,14 +108,14 @@ void usesServerSupportedVersion() {
.hasSize(2)
.map(McpTestRequestRecordingServletFilter.Call::headers)
.allSatisfy(headers -> assertThat(headers).containsEntry("mcp-protocol-version",
ProtocolVersions.MCP_2025_06_18));
ProtocolVersions.MCP_2025_11_25));

assertThat(response).isNotNull();
assertThat(response.content()).hasSize(1)
.first()
.extracting(McpSchema.TextContent.class::cast)
.extracting(McpSchema.TextContent::text)
.isEqualTo(ProtocolVersions.MCP_2025_06_18);
.isEqualTo(ProtocolVersions.MCP_2025_11_25);
mcpServer.close();
}

Expand Down
2 changes: 1 addition & 1 deletion .../main/java/io/modelcontextprotocol/client/transport/WebClientStreamableHttpTransport.java
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Expand Up @@ -510,7 +510,7 @@ public static class Builder {
private boolean openConnectionOnStartup = false;

private List<String> supportedProtocolVersions = List.of(ProtocolVersions.MCP_2024_11_05,
ProtocolVersions.MCP_2025_03_26, ProtocolVersions.MCP_2025_06_18);
ProtocolVersions.MCP_2025_03_26, ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);

private Builder(WebClient.Builder webClientBuilder) {
Assert.notNull(webClientBuilder, "WebClient.Builder must not be null");
Expand Down
2 changes: 1 addition & 1 deletion ...va/io/modelcontextprotocol/server/transport/WebFluxStreamableServerTransportProvider.java
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Expand Up @@ -98,7 +98,7 @@ private WebFluxStreamableServerTransportProvider(McpJsonMapper jsonMapper, Strin
@Override
public List<String> protocolVersions() {
return List.of(ProtocolVersions.MCP_2024_11_05, ProtocolVersions.MCP_2025_03_26,
ProtocolVersions.MCP_2025_06_18);
ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);
}

@Override
Expand Down
10 changes: 5 additions & 5 deletions ...java/io/modelcontextprotocol/WebFluxStreamableHttpVersionNegotiationIntegrationTests.java
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Expand Up @@ -105,22 +105,22 @@ void usesLatestVersion() {
.hasSize(3)
.map(McpTestRequestRecordingExchangeFilterFunction.Call::headers)
.allSatisfy(headers -> assertThat(headers).containsEntry("mcp-protocol-version",
ProtocolVersions.MCP_2025_06_18));
ProtocolVersions.MCP_2025_11_25));

assertThat(response).isNotNull();
assertThat(response.content()).hasSize(1)
.first()
.extracting(McpSchema.TextContent.class::cast)
.extracting(McpSchema.TextContent::text)
.isEqualTo(ProtocolVersions.MCP_2025_06_18);
.isEqualTo(ProtocolVersions.MCP_2025_11_25);
mcpServer.close();
}

@Test
void usesServerSupportedVersion() {
var transport = WebClientStreamableHttpTransport
.builder(WebClient.builder().baseUrl("http://localhost:" + PORT))
.supportedProtocolVersions(List.of(ProtocolVersions.MCP_2025_06_18, "2263-03-18"))
.supportedProtocolVersions(List.of(ProtocolVersions.MCP_2025_11_25, "2263-03-18"))
.build();
var client = McpClient.sync(transport).requestTimeout(Duration.ofHours(10)).build();

Expand All @@ -137,14 +137,14 @@ void usesServerSupportedVersion() {
.hasSize(2)
.map(McpTestRequestRecordingExchangeFilterFunction.Call::headers)
.allSatisfy(headers -> assertThat(headers).containsEntry("mcp-protocol-version",
ProtocolVersions.MCP_2025_06_18));
ProtocolVersions.MCP_2025_11_25));

assertThat(response).isNotNull();
assertThat(response.content()).hasSize(1)
.first()
.extracting(McpSchema.TextContent.class::cast)
.extracting(McpSchema.TextContent::text)
.isEqualTo(ProtocolVersions.MCP_2025_06_18);
.isEqualTo(ProtocolVersions.MCP_2025_11_25);
mcpServer.close();
}

Expand Down
2 changes: 1 addition & 1 deletion ...ava/io/modelcontextprotocol/server/transport/WebMvcStreamableServerTransportProvider.java
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Expand Up @@ -144,7 +144,7 @@ private WebMvcStreamableServerTransportProvider(McpJsonMapper jsonMapper, String
@Override
public List<String> protocolVersions() {
return List.of(ProtocolVersions.MCP_2024_11_05, ProtocolVersions.MCP_2025_03_26,
ProtocolVersions.MCP_2025_06_18);
ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);
}

@Override
Expand Down