Environment Variables

To set a value to an environment variable, use the following syntax:

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env.YOUR_VARIABLE_NAME

Example

Using an environment variable for API key:

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client<llm> MyCustomClient {
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    provider "openai"
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    options {
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        model "gpt-5-mini"
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        // Set the API key using an environment variable
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        api_key env.MY_SUPER_SECRET_API_KEY
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    }
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}

Setting Environment Variables

In the VSCode Playground

Once you open a .baml file in VSCode, you should see a small button over every BAML function: Open Playground. Then you should be able to set environment variables in the settings tab.

Or type BAML Playground in the VSCode Command Bar (CMD + Shift + P or CTRL + Shift + P) to open the playground.

For Boundary Studio Integration

To send logs and traces to Boundary Studio, you need to set the BOUNDARY_API_KEY environment variable. This key is provided when you create an API key in your Boundary Studio dashboard.

$
# .env.local
$
BOUNDARY_API_KEY=your_api_key_here

For Your App (Default)

BAML will do its best to load environment variables from your program. Any of the following strategies for setting env vars are compatible with BAML:

• Setting them in your shell before running your program
• In your Dockerfile
• In your next.config.js
• In your Kubernetes manifest
• From secrets-store.csi.k8s.io
• From a secrets provider such as Infisical / Doppler
• From a .env file (using dotenv CLI)
• Using account credentials for ephemeral token generation (e.g., Vertex AI Auth Tokens)
• python-dotenv package in Python or dotenv package in Node.js

$
export MY_SUPER_SECRET_API_KEY="..."
$
python my_program_using_baml.py

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from dotenv import load_dotenv
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from baml_client import b
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load_dotenv()

Error Handling

Errors for unset environment variables are only thrown when the variable is accessed. If your BAML project has 15 environment variables and 1 is used for the function you are calling, only that one environment variable will be checked for existence.