mcp: update latestProtocolVersion to 2025-11-25 (#724)

Update the SDK to use protocol version 2025-11-25 as the latest
supported version. Fix tests and examples that had hardcoded
expectations for the previous version (2025-06-18).

---------

Co-authored-by: Maciej Kisiel <mkisiel@google.com>

Author: findleyr

docs/protocol.md

@@ -165,7 +165,7 @@ func ExampleStreamableHTTPHandler() {
 	resp := mustPostMessage(`{"jsonrpc": "2.0", "id": 1, "method":"initialize", "params": {}}`, httpServer.URL)
 	fmt.Println(resp)
 	// Output:
-	// {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"logging":{}},"protocolVersion":"2025-06-18","serverInfo":{"name":"server","version":"v0.1.0"}}}
+	// {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"logging":{}},"protocolVersion":"2025-11-25","serverInfo":{"name":"server","version":"v0.1.0"}}}
 }
 ```
 

docs/troubleshooting.md

@@ -50,8 +50,8 @@ func ExampleLoggingTransport() {
 	}
 
 	// Output:
-	// read: {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"logging":{}},"protocolVersion":"2025-06-18","serverInfo":{"name":"server","version":"v0.0.1"}}}
-	// write: {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"clientInfo":{"name":"client","version":"v0.0.1"},"protocolVersion":"2025-06-18","capabilities":{"roots":{"listChanged":true}}}}
+	// read: {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"logging":{}},"protocolVersion":"2025-11-25","serverInfo":{"name":"server","version":"v0.0.1"}}}
+	// write: {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"clientInfo":{"name":"client","version":"v0.0.1"},"protocolVersion":"2025-11-25","capabilities":{"roots":{"listChanged":true}}}}
 	// write: {"jsonrpc":"2.0","method":"notifications/initialized","params":{}}
 }
 ```

mcp/protocol.go

@@ -4,12 +4,6 @@
 
 package mcp
 
-// Protocol types for version 2025-06-18.
-// To see the schema changes from the previous version, run:
-//
-//   prefix=https://raw.githubusercontent.com/modelcontextprotocol/modelcontextprotocol/refs/heads/main/schema
-//   sdiff -l <(curl $prefix/2025-03-26/schema.ts) <(curl $prefix/2025/06-18/schema.ts)
-
 import (
 	"encoding/json"
 	"fmt"

mcp/server_test.go

@@ -763,13 +763,13 @@ func TestClientRootCapabilities(t *testing.T) {
 			var initParams json.RawMessage
 			if tc.capabilities != nil {
 				initParams = json.RawMessage(`{
-					"protocolVersion": "2025-06-18",
+					"protocolVersion": "2025-11-25",
 					"capabilities": ` + *tc.capabilities + `,
 					"clientInfo": {"name": "TestClient", "version": "1.0.0"}
 				}`)
 			} else {
 				initParams = json.RawMessage(`{
-					"protocolVersion": "2025-06-18",
+					"protocolVersion": "2025-11-25",
 					"clientInfo": {"name": "TestClient", "version": "1.0.0"}
 				}`)
 			}

mcp/shared.go

@@ -34,8 +34,8 @@ const (
 	//
 	// It is the version that the client sends in the initialization request, and
 	// the default version used by the server.
-	latestProtocolVersion   = protocolVersion20250618
-	protocolVersion20251125 = "2025-11-25" // not yet released
+	latestProtocolVersion   = protocolVersion20251125
+	protocolVersion20251125 = "2025-11-25"
 	protocolVersion20250618 = "2025-06-18"
 	protocolVersion20250326 = "2025-03-26"
 	protocolVersion20241105 = "2024-11-05"

mcp/streamable_example_test.go

@@ -35,7 +35,7 @@ func ExampleStreamableHTTPHandler() {
 	resp := mustPostMessage(`{"jsonrpc": "2.0", "id": 1, "method":"initialize", "params": {}}`, httpServer.URL)
 	fmt.Println(resp)
 	// Output:
-	// {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"logging":{}},"protocolVersion":"2025-06-18","serverInfo":{"name":"server","version":"v0.1.0"}}}
+	// {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"logging":{}},"protocolVersion":"2025-11-25","serverInfo":{"name":"server","version":"v0.1.0"}}}
 }
 
 // !-streamablehandler

mcp/streamable_test.go

@@ -758,7 +758,7 @@ func TestStreamableServerTransport(t *testing.T) {
 			Logging: &LoggingCapabilities{},
 			Tools:   &ToolCapabilities{ListChanged: true},
 		},
-		ProtocolVersion: latestProtocolVersion,
+		ProtocolVersion: protocolVersion20250618,
 		ServerInfo:      &Implementation{Name: "testServer", Version: "v1.0.0"},
 	}, nil)
 	initializedMsg := req(0, notificationInitialized, &InitializedParams{})

mcp/testdata/conformance/server/version-latest.txtar

@@ -20,7 +20,7 @@ response with its latest supported version.
 		"capabilities": {
 			"logging": {}
 		},
-		"protocolVersion": "2025-06-18",
+		"protocolVersion": "2025-11-25",
 		"serverInfo": {
 			"name": "testServer",
 			"version": "v1.0.0"

mcp/transport_example_test.go

@@ -45,8 +45,8 @@ func ExampleLoggingTransport() {
 	}
 
 	// Output:
-	// read: {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"logging":{}},"protocolVersion":"2025-06-18","serverInfo":{"name":"server","version":"v0.0.1"}}}
-	// write: {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"clientInfo":{"name":"client","version":"v0.0.1"},"protocolVersion":"2025-06-18","capabilities":{"roots":{"listChanged":true}}}}
+	// read: {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"logging":{}},"protocolVersion":"2025-11-25","serverInfo":{"name":"server","version":"v0.0.1"}}}
+	// write: {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"clientInfo":{"name":"client","version":"v0.0.1"},"protocolVersion":"2025-11-25","capabilities":{"roots":{"listChanged":true}}}}
 	// write: {"jsonrpc":"2.0","method":"notifications/initialized","params":{}}
 }