Chat against a stored custom provider record.
The wire format of provider_id is a relay GlobalID (e.g. UHJvdmlkZXI6MTM=). It is decoded to its integer node ID at parse time so downstream consumers don't need to know the GlobalID encoding.
Chat against a Phoenix built-in provider.
Credentials and connection details (base URL, Azure endpoint, AWS region) are resolved from the secret store first and the process environment second. openai_api_type is honoured by the OpenAI and Azure OpenAI branches; other providers ignore it.
Successful Response