Server.version is a plain str defaulting to empty

None and the empty string were never distinguished (the old fallback
used a falsy check, and version, unlike title or description, can
never be omitted from the wire), so the str|None type encoded the same
state twice. The constructor takes version: str = "" on both server
tiers, MCPServer.version returns str, and the two 'or empty' patches
at the identity sites disappear.

No-Verification-Needed: type-narrowing refactor, zero behavior change, full suite green

Author: maxisbey

src/mcp/server/lowlevel/server.py

@@ -131,7 +131,7 @@ def __init__(
         self,
         name: str,
         *,
-        version: str | None = None,
+        version: str = "",
         title: str | None = None,
         description: str | None = None,
         instructions: str | None = None,
@@ -214,7 +214,7 @@ def __init__(
         self,
         name: str,
         *,
-        version: str | None = None,
+        version: str = "",
         title: str | None = None,
         description: str | None = None,
         instructions: str | None = None,
@@ -306,7 +306,7 @@ def __init__(
         self,
         name: str,
         *,
-        version: str | None = None,
+        version: str = "",
         title: str | None = None,
         description: str | None = None,
         instructions: str | None = None,
@@ -539,7 +539,7 @@ def create_initialization_options(
         """
         return InitializationOptions(
             server_name=self.name,
-            server_version=self.version or "",
+            server_version=self.version,
             title=self.title,
             description=self.description,
             capabilities=self.get_capabilities(
@@ -633,7 +633,7 @@ def server_info(self) -> types.Implementation:
         """
         return types.Implementation(
             name=self.name,
-            version=self.version or "",
+            version=self.version,
             title=self.title,
             description=self.description,
             website_url=self.website_url,

src/mcp/server/mcpserver/server.py

@@ -165,7 +165,7 @@ def __init__(
         instructions: str | None = None,
         website_url: str | None = None,
         icons: list[Icon] | None = None,
-        version: str | None = None,
+        version: str = "",
         auth_server_provider: OAuthAuthorizationServerProvider[Any, Any, Any] | None = None,
         token_verifier: TokenVerifier | None = None,
         *,
@@ -290,7 +290,7 @@ def icons(self) -> list[Icon] | None:
         return self._lowlevel_server.icons
 
     @property
-    def version(self) -> str | None:
+    def version(self) -> str:
         return self._lowlevel_server.version
 
     @property