Environment-variable names recognised by llm4s-openai: OpenAI, Requesty, Azure OpenAI and OpenAI embeddings.
These were ConfigKeys.OPENAI_*, ConfigKeys.REQUESTY_BASE_URL and ConfigKeys.AZURE_* in llm4s-core until the providers moved to their own module (#1132): a key belongs with the code that reads it, so that ConfigKeys does not name variables for a provider that may not be on the classpath. ConfigKeys.OPENROUTER_BASE_URL stays in core with OpenRouter, and still names OPENAI_BASE_URL.
Defaults to "https://api.openai.com/v1". Set to an OpenRouter URL (containing "openrouter.ai") to route through OpenRouter without a separate config type - the same org.llm4s.llmconnect.config.OpenAIConfig is reused and the client detects OpenRouter from this URL.
Requesty is an OpenAI-compatible gateway and uses the same OPENAI_BASE_URL variable - there is no separate REQUESTY_BASE_URL. Point OPENAI_BASE_URL at the Requesty router endpoint and configure a named provider with provider = "requesty".