Authentication

Celeste supports two authentication methods: API keys for most providers, and OAuth for Google Cloud APIs.

API Keys (Most Providers)

Environment Variables

Set your API key as an environment variable:

export OPENAI_API_KEY="sk-..."

Or use a .env file:

.env

OPENAI_API_KEY=sk-...
ANTHROPIC_API_KEY=sk-...

Provider Reference

Provider	Environment Variable
OpenAI	`OPENAI_API_KEY`
Anthropic	`ANTHROPIC_API_KEY`
Google (Gemini)	`GOOGLE_API_KEY`
Mistral	`MISTRAL_API_KEY`
Cohere	`COHERE_API_KEY`
ElevenLabs	`ELEVENLABS_API_KEY`
Groq	`GROQ_API_KEY`
BFL	`BFL_API_KEY`
DeepSeek	`DEEPSEEK_API_KEY`
xAI	`XAI_API_KEY`

Google Cloud (OAuth)

Google Cloud APIs (like Cloud TTS with Gemini voices) require OAuth authentication instead of API keys.

Setup

Install the gcloud CLI
Login with Application Default Credentials:

gcloud auth application-default login

Set your project (for billing/quota):

gcloud config set project YOUR_PROJECT_ID

Usage

import celeste

# No API key needed - uses OAuth automatically
response = await celeste.audio.speak(
    model="gemini-2.5-flash-tts",
    provider="google",
    text="Hello from Google Cloud",
)

Troubleshooting

Error	Solution
`RefreshError: Reauthentication is needed`	Run `gcloud auth application-default login`
Quota/project errors	Run `gcloud config set project YOUR_PROJECT_ID`

Explicit Authentication

Override environment variables by passing api_key directly:

import celeste

response = await celeste.text.generate(
    model="gpt-4o",
    api_key="sk-...",
    prompt="Hello",
)

Advanced: custom auth headers

For custom headers, use create_client with the auth parameter:

import celeste
from celeste import APIKey

client = celeste.create_client(
    modality="text",
    auth=APIKey(
        key="sk-...",
        header="X-Custom-Header",
    ),
)

Authentication

On this page