Add 2025-11-25 spec version to all transports (#1025)

Signed-off-by: Dariusz Jędrzejczyk <2554306+chemicL@users.noreply.github.com>

Author: chemicL

MIGRATION-2.0.md

@@ -215,6 +215,18 @@ The deprecated `Builder.customizeRequest(Consumer<HttpRequest.Builder>)` method
 
 **Action:** Use `requestBuilder(HttpRequest.Builder)` for static request setup, or `httpRequestCustomizer(McpSyncHttpClientRequestCustomizer)` for per-request customization.
 
+### `protocolVersions()` default now advertises all known versions
+
+The default implementation of `protocolVersions()` on `McpTransport` and `McpServerTransportProviderBase` previously returned only `["2024-11-05"]`. It now returns all four versions the SDK understands:
+
+```
+["2024-11-05", "2025-03-26", "2025-06-18", "2025-11-25"]
+```
+
+**Impact for transport implementors:** If your custom `McpClientTransport` or `McpServerTransportProvider` did not override `protocolVersions()`, it will now advertise all four versions during protocol negotiation instead of just `2024-11-05`. This is the intended upgrade path for most transports, but if you need to restrict your transport to a specific set of versions, override `protocolVersions()` explicitly and return the desired list.
+
+**Impact for users of built-in transports:** No action is required. `StdioClientTransport`, `StdioServerTransportProvider`, and `HttpServletStreamableServerTransportProvider` all advertise the full version list.
+
 ### SSE transports are deprecated
 
 The HTTP+SSE client and server transports (and their supporting validator/exception types) are deprecated in favour of Streamable HTTP — `HttpClientStreamableHttpTransport` on the client, and `HttpServletStreamableServerTransportProvider` on the server. They still work; plan a move to Streamable HTTP.

mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java

@@ -27,7 +27,6 @@
 import io.modelcontextprotocol.spec.McpStreamableServerSession;
 import io.modelcontextprotocol.spec.McpStreamableServerTransport;
 import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
-import io.modelcontextprotocol.spec.ProtocolVersions;
 import io.modelcontextprotocol.util.Assert;
 import io.modelcontextprotocol.json.McpJsonDefaults;
 import io.modelcontextprotocol.json.McpJsonMapper;
@@ -166,12 +165,6 @@ 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_11_25);
-	}
-
 	@Override
 	public void setSessionFactory(McpStreamableServerSession.Factory sessionFactory) {
 		this.sessionFactory = sessionFactory;

mcp-core/src/main/java/io/modelcontextprotocol/server/transport/StdioServerTransportProvider.java

@@ -22,7 +22,6 @@
 import io.modelcontextprotocol.spec.McpServerSession;
 import io.modelcontextprotocol.spec.McpServerTransport;
 import io.modelcontextprotocol.spec.McpServerTransportProvider;
-import io.modelcontextprotocol.spec.ProtocolVersions;
 import io.modelcontextprotocol.util.Assert;
 import io.modelcontextprotocol.json.McpJsonMapper;
 import org.slf4j.Logger;
@@ -82,11 +81,6 @@ public StdioServerTransportProvider(McpJsonMapper jsonMapper, InputStream inputS
 		this.outputStream = outputStream;
 	}
 
-	@Override
-	public List<String> protocolVersions() {
-		return List.of(ProtocolVersions.MCP_2024_11_05);
-	}
-
 	@Override
 	public void setSessionFactory(McpServerSession.Factory sessionFactory) {
 		// Create a single session for the stdio connection

mcp-core/src/main/java/io/modelcontextprotocol/spec/McpServerTransportProviderBase.java

@@ -82,7 +82,8 @@ default void close() {
 	 * @return the protocol version as a string
 	 */
 	default List<String> protocolVersions() {
-		return List.of(ProtocolVersions.MCP_2024_11_05);
+		return List.of(ProtocolVersions.MCP_2024_11_05, ProtocolVersions.MCP_2025_03_26,
+				ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);
 	}
 
 }

mcp-core/src/main/java/io/modelcontextprotocol/spec/McpTransport.java

@@ -101,7 +101,8 @@ static boolean isPeerClosed(Throwable t) {
 	<T> T unmarshalFrom(Object data, TypeRef<T> typeRef);
 
 	default List<String> protocolVersions() {
-		return List.of(ProtocolVersions.MCP_2024_11_05);
+		return List.of(ProtocolVersions.MCP_2024_11_05, ProtocolVersions.MCP_2025_03_26,
+				ProtocolVersions.MCP_2025_06_18, ProtocolVersions.MCP_2025_11_25);
 	}
 
 }