fix: handle typing_extensions import properly on Python 3.11+

The SDK unconditionally imported `typing_extensions.NotRequired`, but `typing_extensions` is declared as a dependency only for Python < 3.11 in pyproject.toml. On Python 3.11+ this led to a ModuleNotFoundError on a clean install.

This commit replaces the unconditional import with a version-guarded

src/claude_code_sdk/types.py

@@ -1,10 +1,14 @@
 """Type definitions for Claude SDK."""
 
+import sys
 from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Any, Literal, TypedDict
 
-from typing_extensions import NotRequired  # For Python < 3.11 compatibility
+if sys.version_info >= (3, 11):
+    from typing import NotRequired
+else:
+    from typing_extensions import NotRequired
 
 # Permission modes
 PermissionMode = Literal["default", "acceptEdits", "bypassPermissions"]

tests/test_types.py

@@ -1,5 +1,8 @@
 """Tests for Claude SDK type definitions."""
 
+import sys
+import importlib
+import pytest
 from claude_code_sdk import (
     AssistantMessage,
     ClaudeCodeOptions,
@@ -56,6 +59,14 @@ class TestMessageTypes:
         assert msg.total_cost_usd == 0.01
         assert msg.session_id == "session-123"
 
+    def test_import_types_module(self):
+        """
+        Smoke test to ensure claude_code_sdk.types imports without errors
+        and defines NotRequired.
+        """
+        module = importlib.reload(importlib.import_module("claude_code_sdk.types"))
+        assert hasattr(module, "NotRequired"), "claude_code_sdk.types should define NotRequired"
+
 
 class TestOptions:
     """Test Options configuration."""