Update protocol version handling

Author: jspahrsummers

mcp_python/client/session.py

@@ -2,8 +2,9 @@
 from pydantic import AnyUrl
 
 from mcp_python.shared.session import BaseSession
-from mcp_python.shared.version import SUPPORTED_PROTOCOL_VERSION
+from mcp_python.shared.version import SUPPORTED_PROTOCOL_VERSIONS
 from mcp_python.types import (
+    LATEST_PROTOCOL_VERSION,
     CallToolResult,
     ClientCapabilities,
     ClientNotification,
@@ -49,7 +50,7 @@ async def initialize(self) -> InitializeResult:
                 InitializeRequest(
                     method="initialize",
                     params=InitializeRequestParams(
-                        protocolVersion=SUPPORTED_PROTOCOL_VERSION,
+                        protocolVersion=LATEST_PROTOCOL_VERSION,
                         capabilities=ClientCapabilities(
                             sampling=None, experimental=None
                         ),
@@ -60,7 +61,7 @@ async def initialize(self) -> InitializeResult:
             InitializeResult,
         )
 
-        if result.protocolVersion != SUPPORTED_PROTOCOL_VERSION:
+        if result.protocolVersion not in SUPPORTED_PROTOCOL_VERSIONS:
             raise RuntimeError(
                 "Unsupported protocol version from the server: "
                 f"{result.protocolVersion}"

mcp_python/server/session.py

@@ -11,8 +11,8 @@
     BaseSession,
     RequestResponder,
 )
-from mcp_python.shared.version import SUPPORTED_PROTOCOL_VERSION
 from mcp_python.types import (
+    LATEST_PROTOCOL_VERSION,
     ClientNotification,
     ClientRequest,
     CreateMessageResult,
@@ -67,7 +67,7 @@ async def _received_request(
                 await responder.respond(
                     ServerResult(
                         InitializeResult(
-                            protocolVersion=SUPPORTED_PROTOCOL_VERSION,
+                            protocolVersion=LATEST_PROTOCOL_VERSION,
                             capabilities=self._init_options.capabilities,
                             serverInfo=Implementation(
                                 name=self._init_options.server_name,

mcp_python/shared/version.py

@@ -1 +1,3 @@
-SUPPORTED_PROTOCOL_VERSION = 1
+from mcp_python.types import LATEST_PROTOCOL_VERSION
+
+SUPPORTED_PROTOCOL_VERSIONS = [1, LATEST_PROTOCOL_VERSION]

tests/client/test_session.py

@@ -3,6 +3,7 @@
 
 from mcp_python.client.session import ClientSession
 from mcp_python.types import (
+    LATEST_PROTOCOL_VERSION,
     ClientNotification,
     ClientRequest,
     Implementation,
@@ -41,7 +42,7 @@ async def mock_server():
 
         result = ServerResult(
             InitializeResult(
-                protocolVersion=1,
+                protocolVersion=LATEST_PROTOCOL_VERSION,
                 capabilities=ServerCapabilities(
                     logging=None,
                     resources=None,
@@ -88,7 +89,7 @@ async def listen_session():
 
     # Assert the result
     assert isinstance(result, InitializeResult)
-    assert result.protocolVersion == 1
+    assert result.protocolVersion == LATEST_PROTOCOL_VERSION
     assert isinstance(result.capabilities, ServerCapabilities)
     assert result.serverInfo == Implementation(name="mock-server", version="0.1.0")
 

tests/test_types.py

@@ -1,4 +1,4 @@
-from mcp_python.types import ClientRequest, JSONRPCMessage, JSONRPCRequest
+from mcp_python.types import LATEST_PROTOCOL_VERSION, ClientRequest, JSONRPCMessage, JSONRPCRequest
 
 
 def test_jsonrpc_request():
@@ -7,7 +7,7 @@ def test_jsonrpc_request():
         "id": 1,
         "method": "initialize",
         "params": {
-            "protocolVersion": 1,
+            "protocolVersion": LATEST_PROTOCOL_VERSION,
             "capabilities": {"batch": None, "sampling": None},
             "clientInfo": {"name": "mcp_python", "version": "0.1.0"},
         },
@@ -21,4 +21,4 @@ def test_jsonrpc_request():
     assert request.root.id == 1
     assert request.root.method == "initialize"
     assert request.root.params is not None
-    assert request.root.params["protocolVersion"] == 1
+    assert request.root.params["protocolVersion"] == LATEST_PROTOCOL_VERSION