When adding or extending client/provider integrations, enforce a single, predictable configuration-resolution contract:

• Args → env fallbacks: For each required setting (e.g., api_version, region), accept an explicit argument, otherwise fall back to the corresponding environment variable(s). Only raise a clear error when neither is provided.
• Keep derived config coherent on overrides: If your client derives other settings from config (e.g., base_url derived from region), then copy()/cloning/overrides must recompute or correctly forward dependent values so behavior matches the updated config.
• Prevent invalid config-mode switches: If auth modes are mutually exclusive (e.g., SigV4 vs API key, or token vs API key), ensure copy() clears/normalizes incompatible fields instead of forwarding stale state.
• Stability across releases & feature flags:
  • If an integration requires adding public exports (like __init__.py), update the generator configuration so the change persists across automated releases.
  • Manage optional feature dependencies (e.g., async HTTP support) via extras/feature flags and raise a focused runtime error when the optional dependency isn’t installed.

Example patterns:

# 1) Env fallback + clear error
resolved_api_version = api_version or os.environ.get("OPENAI_API_VERSION")
if not resolved_api_version:
    raise ValueError("Must provide api_version or set OPENAI_API_VERSION")

# 2) copy(): keep dependent config consistent
new_region = region or self._region
# ensure base_url is recalculated when region changes
_forward_base_url = {} if region else {"base_url": self.base_url}

# 3) copy(): normalize mutually-exclusive auth fields
# if switching to api_key, drop credential provider
forwarded_credential_provider = None if "api_key" in kwargs else (credential_provider or self._credential_provider)

Add unit tests that cover:

• override of primary config triggers correct recomputation of dependent config (e.g., region → base_url),
• explicit switches between mutually exclusive auth modes behave as expected,
• missing required config produces the intended error message and does not fail later with confusing downstream exceptions.