Well-known providers mapped to the env var that holds their API key.
Used by has_provider_credentials to verify credentials before model
creation, so the UI can show a warning icon and a specific error message
(e.g., "ANTHROPIC_API_KEY not set") instead of letting the provider fail at call
time.
Providers not listed here fall through to the config-file check or the langchain registry fallback.
PROVIDER_API_KEY_ENV: dict[str, str] = {'anthropic': 'ANTHROPIC_API_KEY', 'azure_openai': 'AZURE_OPENAI_API_KEY', 'cohere': 'COHERE_API_KEY', 'deepseek': 'DEEPSEEK_API_KEY', 'fireworks': 'FIREWORKS_API_KEY', 'google_genai': 'GOOGLE_API_KEY', 'google_vertexai': 'GOOGLE_CLOUD_PROJECT', 'groq': 'GROQ_API_KEY', 'huggingface': 'HUGGINGFACEHUB_API_TOKEN', 'ibm': 'WATSONX_APIKEY', 'mistralai': 'MISTRAL_API_KEY', 'nvidia': 'NVIDIA_API_KEY', 'openai': 'OPENAI_API_KEY', 'openrouter': 'OPENROUTER_API_KEY', 'perplexity': 'PPLX_API_KEY', 'together': 'TOGETHER_API_KEY', 'xai': 'XAI_API_KEY'}