openai/openai-python · error · ValueError

The `default_headers` and `set_default_headers` arguments ar

Error message

The `default_headers` and `set_default_headers` arguments are mutually exclusive

What it means

`copy()`/`with_options()` distinguishes replacing headers (`set_default_headers`) from merging into existing ones (`default_headers`). Passing both makes the semantics ambiguous, so the sync Bedrock client raises a ValueError.

Source

Thrown at src/openai/lib/bedrock.py:575

        max_retries: int | NotGiven = NOT_GIVEN,
        default_headers: Mapping[str, str] | None = None,
        set_default_headers: Mapping[str, str] | None = None,
        default_query: Mapping[str, object] | None = None,
        set_default_query: Mapping[str, object] | None = None,
        _enforce_credentials: bool | None = None,
        _extra_kwargs: Mapping[str, Any] = {},
    ) -> Self:
        if data_residency is not None:
            raise OpenAIError("`data_residency` is only supported by OpenAI clients")
        base_url = None if isinstance(base_url, NotGiven) else base_url
        if callable(api_key):
            raise OpenAIError("Pass refreshable Bedrock credentials via `bedrock_token_provider`, not `api_key`.")
        if not isinstance(provider, NotGiven):
            raise OpenAIError("Configure `provider` on `OpenAI`, not on `BedrockOpenAI.with_options()`.")
        if admin_api_key is not None or workload_identity is not None:
            raise OpenAIError("BedrockOpenAI only supports Bedrock bearer token or AWS credential authentication.")
        if default_headers is not None and set_default_headers is not None:
            raise ValueError("The `default_headers` and `set_default_headers` arguments are mutually exclusive")
        if default_query is not None and set_default_query is not None:
            raise ValueError("The `default_query` and `set_default_query` arguments are mutually exclusive")

        headers = self._custom_headers
        if default_headers is not None:
            headers = {**headers, **default_headers}
        elif set_default_headers is not None:
            headers = set_default_headers
        params = self._custom_query
        if default_query is not None:
            params = {**params, **default_query}
        elif set_default_query is not None:
            params = set_default_query

        provider_kwargs, inherited_provider, inherited_state = _copy_configuration(
            self,
            api_key=api_key,
            token_provider=bedrock_token_provider,

View on GitHub (pinned to 9917c6e28e)

Solutions

1. Pick one: `default_headers` to merge with the client's current headers, or `set_default_headers` to replace them
2. Combine your header dicts yourself and pass the merged dict to one argument

Example fix

# before
c = bedrock_client.with_options(default_headers={'X-A':'1'}, set_default_headers={'X-B':'2'})
# after
c = bedrock_client.with_options(set_default_headers={'X-A':'1','X-B':'2'})

assert not (default_headers is not None and set_default_headers is not None)

When it happens

Trigger: `bedrock_client.with_options(default_headers={'X-A':'1'}, set_default_headers={'X-B':'2'})` — both arguments non-None.

Common situations: Delegating builder functions that forward a headers dict to both parameters; merging config presets where one sets `default_headers` and another sets `set_default_headers`.

Related errors

• The `default_query` and `set_default_query` arguments are mu
• `data_residency` is only supported by OpenAI clients
• Configure `provider` on `OpenAI`, not on `BedrockOpenAI.with
• BedrockOpenAI only supports Bedrock bearer token or AWS cred
• Configure `provider` on `AsyncOpenAI`, not on `AsyncBedrockO

AI-assisted analysis of openai/openai-python@9917c6e28e (2026-08-28). Data as JSON: /api/errors/1d2e176279313154. Report an issue: GitHub.