Update MCP protocol validation and defaults (#17)

Author: soodoku

rmcp/core/server.py

@@ -33,7 +33,7 @@
     _SUPPORTED_LOG_LEVELS = ["debug", "info", "warning", "error"]
 except Exception:  # pragma: no cover - optional dependency
     _MCP_TYPES_AVAILABLE = False
-    _PROTOCOL_VERSION = "2025-06-18"
+    _PROTOCOL_VERSION = "2025-11-25"
     _SUPPORTED_LOG_LEVELS = [
         "debug",
         "info",

rmcp/transport/http.py

@@ -150,7 +150,8 @@ def __init__(
 ## Protocol
 
 This server implements the Model Context Protocol (MCP) specification for statistical analysis tools.
-All requests after initialization must include the `MCP-Protocol-Version: 2025-06-18` header.
+All requests after initialization must include the `MCP-Protocol-Version` header. Use `2025-11-25`
+for the latest spec (preferred); `2025-06-18` remains supported for compatibility.
             """.strip(),
             contact={
                 "name": "RMCP Project",
@@ -218,16 +219,29 @@ def _validate_origin(self, request: Request) -> None:
     def _validate_protocol_version(self, request: Request, method: str) -> None:
         """Validate MCP-Protocol-Version header according to MCP specification."""
         protocol_version = request.headers.get("mcp-protocol-version")
-        supported_versions = ("2025-06-18",)
+        supported_versions = ("2025-11-25", "2025-06-18")
+        preferred_version = supported_versions[0]
 
         if method == "initialize":
             # Initialize requests don't require the header (it's set after negotiation)
-            if protocol_version and protocol_version not in supported_versions:
+            if not protocol_version:
+                # Default to the latest version when the client doesn't specify one
+                request.state.protocol_version = preferred_version
+                return
+            if protocol_version not in supported_versions:
                 raise HTTPException(
                     400,
                     f"Unsupported protocol version: {protocol_version}. "
                     f"Supported versions: {', '.join(supported_versions)}",
                 )
+            if protocol_version != preferred_version:
+                logger.info(
+                    "Client requested older MCP protocol version %s; "
+                    "preferring %s for responses",
+                    protocol_version,
+                    preferred_version,
+                )
+            request.state.protocol_version = protocol_version
         else:
             # All non-initialize requests MUST include the MCP-Protocol-Version header
             if not protocol_version:
@@ -281,7 +295,8 @@ def _setup_routes(self) -> None:
 
             **Required Headers:**
             - `Content-Type: application/json`
-            - `MCP-Protocol-Version: 2025-06-18` (after initialization)
+            - `MCP-Protocol-Version: 2025-11-25` (preferred after initialization; `2025-06-18`
+              remains supported)
 
             **Session Management:**
             Sessions must be initialized before other operations.
@@ -501,8 +516,8 @@ async def landing_page() -> Response:
                     <pre style="background: #f4f4f4; padding: 15px; border-radius: 4px; overflow-x: auto;">
 curl -X POST https://rmcp-server-394229601724.us-central1.run.app/mcp \\
   -H "Content-Type: application/json" \\
-  -H "MCP-Protocol-Version: 2025-06-18" \\
-  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"test-client","version":"1.0"}}}'</pre>
+  -H "MCP-Protocol-Version: 2025-11-25" \\
+  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-11-25","capabilities":{},"clientInfo":{"name":"test-client","version":"1.0"}}}'</pre>
 
                     <div class="footer">
                         <p>RMCP v0.5.1 | MIT License | <a href="https://github.com/finite-sample/rmcp">GitHub</a></p>

tests/integration/protocol/test_mcp_protocol_compliance.py

@@ -1,8 +1,9 @@
 """
 MCP Protocol Compliance Tests
 
-Tests that RMCP correctly implements the Model Context Protocol 2025-06-18 specification
-that Claude Desktop, Cursor, VS Code, and other MCP clients expect.
+Tests that RMCP correctly implements the Model Context Protocol 2025-11-25 specification
+while maintaining compatibility with the 2025-06-18 clients that Claude Desktop, Cursor,
+VS Code, and other MCP clients expect.
 
 These tests simulate the exact JSON-RPC message sequences that IDEs send.
 """
@@ -411,7 +412,7 @@ async def test_complete_mcp_conversation():
 def test_mcp_protocol_version_compatibility():
     """Test that RMCP declares compatibility with the correct MCP version."""
     # This test doesn't need async since it's just checking constants
-    expected_version = "2025-06-18"
+    expected_version = "2025-11-25"
 
     # Check that our server reports the correct protocol version
     # This would be checked during initialization in real usage