Function openai_provider_api_key 

pub fn openai_provider_api_key(
    provider_id: &str,
    cfg: &ProviderConfig,
) -> Option<String>

Resolve an OpenAI-compatible provider key from its explicit config or a known provider’s canonical environment variable. Arbitrary custom provider ids must declare apiKey: "$ENV": deriving an env name by normalizing the id would collapse distinct native-Pi identities such as a-b and a_b.