def test_app_config_extended_default(tmp_path: os.PathLike) -> None:
    """Test default behavior when no [extended] section exists.

    This test verifies that if there is no [extended] section in the TOML file,
    OpenHandsConfig.extended remains its default (empty) ExtendedConfig.
    """
    config_content = """
[core]
workspace_base = "/tmp/workspace"

[llm]
model = "test-model"
api_key = "toml-api-key"

[agent]
enable_prompt_extensions = true
"""
    config_file = tmp_path / 'config.toml'
    config_file.write_text(config_content)

    config = OpenHandsConfig()
    load_from_toml(config, str(config_file))

    # Extended config should be empty
    assert config.extended.root == {}
Test default behavior when no [extended] section exists.

    This test verifies that if there is no [extended] section in the TOML file,
    OpenHandsConfig.extended remains its default (empty) ExtendedConfig.
    
tests/unit/test_config_extended.py