Merge branch 'main' of https://github.com/finite-sample/rmcp

Author: soodoku

rmcp/core/server.py

@@ -44,6 +44,11 @@
         "alert",
         "emergency",
     ]
+# Supported MCP protocol versions (latest first)
+_SUPPORTED_PROTOCOL_VERSIONS = tuple(
+    dict.fromkeys((_PROTOCOL_VERSION, "2025-06-18"))
+)
+
 # Import version from __init__ at runtime to avoid circular imports
 from ..registries.prompts import PromptsRegistry
 from ..registries.resources import ResourcesRegistry
@@ -466,6 +471,15 @@ async def _handle_initialize(self, params: dict[str, Any]) -> dict[str, Any]:
         Returns:
             Initialize response with server capabilities
         """
+        requested_version = params.get("protocolVersion")
+        if requested_version and requested_version not in _SUPPORTED_PROTOCOL_VERSIONS:
+            raise ValueError(
+                "Unsupported protocol version requested: "
+                f"{requested_version}. Supported versions: "
+                f"{', '.join(_SUPPORTED_PROTOCOL_VERSIONS)}"
+            )
+        protocol_version = requested_version or _PROTOCOL_VERSION
+
         client_info = params.get("clientInfo", {})
         logger.info(
             f"Initializing MCP connection with client: "
@@ -480,7 +494,7 @@ async def _handle_initialize(self, params: dict[str, Any]) -> dict[str, Any]:
                 logging=LoggingCapability(),
             )
             initialize_result = InitializeResult(
-                protocolVersion=_PROTOCOL_VERSION,
+                protocolVersion=protocol_version,
                 capabilities=capabilities,
                 serverInfo=Implementation(name=self.name, version=self.version),
                 instructions=self.description or None,
@@ -495,7 +509,7 @@ async def _handle_initialize(self, params: dict[str, Any]) -> dict[str, Any]:
             "completion": {},
         }
         result = {
-            "protocolVersion": _PROTOCOL_VERSION,
+            "protocolVersion": protocol_version,
             "capabilities": capabilities_dict,
             "serverInfo": {"name": self.name, "version": self.version},
         }

rmcp/transport/http.py

@@ -25,6 +25,7 @@
         "HTTP transport requires 'fastapi' extras. Install with: pip install rmcp[http]"
     ) from e
 from ..config import get_config
+from ..core.server import _SUPPORTED_PROTOCOL_VERSIONS
 from .base import Transport
 
 logger = logging.getLogger(__name__)
@@ -219,7 +220,7 @@ 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 = ("2025-11-25", "2025-06-18")
+        supported_versions = _SUPPORTED_PROTOCOL_VERSIONS
         preferred_version = supported_versions[0]
 
         if method == "initialize":
@@ -325,6 +326,11 @@ async def handle_jsonrpc(request: Request) -> Response:
                 self._check_session_initialized(session_id, method)
                 # Track initialize completion
                 if method == "initialize":
+                    params = message.setdefault("params", {})
+                    if "protocolVersion" not in params and hasattr(
+                        request.state, "protocol_version"
+                    ):
+                        params["protocolVersion"] = request.state.protocol_version
                     self._initialized_sessions.add(session_id)
                     self._sessions[session_id]["initialized"] = True
                 # Process through message handler