diff --git a/python/packages/autogen-ext/tests/test_encoding.py b/python/packages/autogen-ext/tests/test_encoding.py
new file mode 100644
index 000000000000..8a4ce3792d5d
--- /dev/null
+++ b/python/packages/autogen-ext/tests/test_encoding.py
@@ -0,0 +1,164 @@
+"""
+Tests for UTF-8 encoding support in autogen-ext.
+
+Verifies that all file operations use explicit encoding="utf-8"
+to prevent UnicodeDecodeError in non-English environments.
+
+Related Issue: https://github.com/microsoft/autogen/issues/5566
+"""
+
+import os
+import tempfile
+import pytest
+from pathlib import Path
+import ast
+import inspect
+
+
+class TestEncodingSupport:
+    """
+    Test suite for UTF-8 encoding support.
+    
+    These tests prevent regression of the fix for Issue #5566,
+    where PlaywrightController failed with UnicodeDecodeError
+    on non-English systems (e.g., Chinese Windows with cp950 encoding).
+    """
+
+    def test_playwright_controller_script_loading(self):
+        """
+        Test that PlaywrightController can load page_script.js 
+        in non-ASCII environments.
+        
+        This is a regression test for Issue #5566.
+        """
+        # Read the actual file to verify encoding parameter exists
+        from autogen_ext.agents.web_surfer import PlaywrightController
+        
+        # Verify the source code contains encoding parameter
+        source_file = inspect.getfile(PlaywrightController)
+        with open(source_file, "r", encoding="utf-8") as f:
+            content = f.read()
+        
+        # Check that the open() call for page_script.js has encoding
+        assert 'encoding="utf-8"' in content, \
+            "PlaywrightController should use encoding='utf-8' when loading page_script.js"
+
+    def test_file_operations_with_utf8_encoding(self):
+        """
+        Test that file operations handle UTF-8 content correctly.
+        
+        Simulates a non-ASCII environment by writing and reading
+        a file with Chinese characters and emoji.
+        """
+        test_content = "测试内容 🚀 Emoji support"
+        
+        with tempfile.NamedTemporaryFile(
+            mode='w', 
+            encoding='utf-8', 
+            delete=False, 
+            suffix='.txt'
+        ) as f:
+            f.write(test_content)
+            temp_path = f.name
+        
+        try:
+            # Read file with explicit encoding (correct way)
+            with open(temp_path, 'r', encoding='utf-8') as f:
+                content = f.read()
+                assert content == test_content, \
+                    "File content should match when using encoding='utf-8'"
+        finally:
+            os.unlink(temp_path)
+
+    @pytest.mark.asyncio
+    async def test_multimodal_web_surfer_encoding(self):
+        """
+        Test that MultimodalWebSurfer handles UTF-8 content correctly.
+        
+        Note: This is a placeholder test. In actual implementation,
+        you would mock the Playwright page and test the surfer's
+        ability to handle UTF-8 content.
+        """
+        # Placeholder - actual implementation would require
+        # mocking Playwright's Page object
+        pass
+
+
+def test_no_encoding_issues_in_source():
+    """
+    Static test to check that all open() calls in the source code
+    use explicit encoding parameter.
+    
+    This test should be run during linting/CI to prevent
+    future encoding issues.
+    
+    Related Issue: https://github.com/microsoft/autogen/issues/5566
+    """
+    import ast
+    import inspect
+    
+    # Get the source file path
+    from autogen_ext.agents import web_surfer
+    source_file = inspect.getfile(web_surfer)
+    
+    with open(source_file, 'r', encoding='utf-8') as f:
+        tree = ast.parse(f.read())
+    
+    # Walk the AST to find all open() calls
+    issues_found = []
+    
+    for node in ast.walk(tree):
+        if isinstance(node, ast.Call):
+            # Check if this is an open() call
+            if isinstance(node.func, ast.Name) and node.func.id == 'open':
+                # Check if encoding parameter is provided
+                has_encoding = False
+                for keyword in node.keywords:
+                    if keyword.arg == 'encoding':
+                        has_encoding = True
+                        break
+                
+                # Check positional arguments (mode should be the 2nd arg)
+                # If mode is specified and is text mode ('r' or 'w'),
+                # encoding should be provided
+                if len(node.args) >= 2:
+                    mode_arg = node.args[1]
+                    if isinstance(mode_arg, ast.Constant) and 't' in str(mode_arg.value):
+                        if not has_encoding:
+                            issues_found.append({
+                                'line': node.lineno,
+                                'message': 'open() call without encoding parameter in text mode'
+                            })
+    
+    if issues_found:
+        pytest.fail(
+            f"Found {len(issues_found)} open() calls without encoding parameter:\n" +
+            "\n".join([f"  Line {i['line']}: {i['message']}" for i in issues_found])
+        )
+
+
+def test_page_script_js_is_valid_utf8():
+    """
+    Test that page_script.js is valid UTF-8.
+    
+    This ensures the file itself won't cause encoding issues
+    when loaded by PlaywrightController.
+    """
+    from autogen_ext.agents.web_surfer import PlaywrightController
+    
+    # Get the path to page_script.js
+    source_file = inspect.getfile(PlaywrightController)
+    page_script_path = Path(source_file).parent / "page_script.js"
+    
+    # Verify the file exists and is valid UTF-8
+    assert page_script_path.exists(), "page_script.js should exist"
+    
+    with open(page_script_path, 'r', encoding='utf-8') as f:
+        content = f.read()
+        # Basic sanity check
+        assert len(content) > 0, "page_script.js should not be empty"
+        assert 'function' in content, "page_script.js should contain JavaScript functions"
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])