## Authentication Setup

The Gemini CLI requires you to authenticate with Google's AI services. On initial startup you'll need to configure **one** of the following authentication methods:

1.  **Login with Google (Gemini Code Assist):**

    - Use this option to log in with the standard, free account you use for services like Gmail, Google Photos, and Google Drive for personal use (e.g. your-name@gmail.com).
    - During initial startup, Gemini CLI will direct you to a webpage for authentication. Once authenticated, your credentials will be cached locally so the web login can be skipped on subsequent runs.
    - Note that the web login must be done in a browser that can communicate with the machine Gemini CLI is being run from. (Specifically, the browser will be redirected to a localhost url that Gemini CLI will be listening on).

2.  **Gemini API key:**

    - Obtain your API key from Google AI Studio: [https://aistudio.google.com/app/apikey](https://aistudio.google.com/app/apikey)
    - Set the `GEMINI_API_KEY` environment variable. In the following methods, replace `YOUR_GEMINI_API_KEY` with the API key you obtained from Google AI Studio:
      - You can temporarily set the environment variable in your current shell session using the following command:
        ```bash
        export GEMINI_API_KEY="YOUR_GEMINI_API_KEY"
        ```
      - For repeated use, you can add the environment variable to your `.env` file (located in the project directory or user home directory) or your shell's configuration file (like `~/.bashrc`, `~/.zshrc`, or `~/.profile`). For example, the following command adds the environment variable to a `~/.bashrc` file:
        ```bash
        echo 'export GEMINI_API_KEY="YOUR_GEMINI_API_KEY"' >> ~/.bashrc
        source ~/.bashrc
        ```

3.  **Login with Google Workspace**

    - Use this option to log in with the **Google Workspace Accounts**. This is a paid service for businesses and organizations that provides a suite of productivity tools, including a custom email domain (e.g. your-name@your-company.com), enhanced security features, and administrative controls. These accounts are often managed by an employer or school.
      - Google Workspace Account must configure a Google Cloud Project Id to use. You can temporarily set the environment variable in your current shell session using the following command:
      ```bash
      export GOOGLE_CLOUD_PROJECT_ID="YOUR_PROJECT_ID"
      ```
      - For repeated use, you can add the environment variable to your `.env` file (located in the project directory or user home directory) or your shell's configuration file (like `~/.bashrc`, `~/.zshrc`, or `~/.profile`). For example, the following command adds the environment variable to a `~/.bashrc` file:
      ```bash
      echo 'export GOOGLE_CLOUD_PROJECT_ID="YOUR_PROJECT_ID"' >> ~/.bashrc
      source ~/.bashrc
      ```
    - During startup, Gemini CLI will direct you to a webpage for authentication. Once authenticated, your credentials will be cached locally so the web login can be skipped on subsequent runs.
    - Note that the web login must be done in a browser that can communicate with the machine Gemini CLI is being run from. (Specifically, the browser will be redirected to a localhost url that Gemini CLI will be listening on).

4.  **Vertex AI:**
    - If not using express mode:
      - Ensure you have a Google Cloud project and have enabled the Vertex AI API.
      - Set up Application Default Credentials (ADC), using the following command:
        ```bash
        gcloud auth application-default login
        ```
        For more information, see [Set up Application Default Credentials for Google Cloud](https://cloud.google.com/docs/authentication/provide-credentials-adc).
      - Set the `GOOGLE_CLOUD_PROJECT`, `GOOGLE_CLOUD_LOCATION`, and `GOOGLE_GENAI_USE_VERTEXAI` environment variables. In the following methods, replace `YOUR_PROJECT_ID` and `YOUR_PROJECT_LOCATION` with the relevant values for your project:
        - You can temporarily set these environment variables in your current shell session using the following commands:
          ```bash
          export GOOGLE_CLOUD_PROJECT="YOUR_PROJECT_ID"
          export GOOGLE_CLOUD_LOCATION="YOUR_PROJECT_LOCATION" # e.g., us-central1
          export GOOGLE_GENAI_USE_VERTEXAI=true
          ```
        - For repeated use, you can add the environment variables to your `.env` file (located in the project directory or user home directory) or your shell's configuration file (like `~/.bashrc`, `~/.zshrc`, or `~/.profile`). For example, the following commands adds the environment variables to a `~/.bashrc` file:
          ```bash
          echo 'export GOOGLE_CLOUD_PROJECT="YOUR_PROJECT_ID"' >> ~/.bashrc
          echo 'export GOOGLE_CLOUD_LOCATION="YOUR_PROJECT_LOCATION"' >> ~/.bashrc
          echo 'export GOOGLE_GENAI_USE_VERTEXAI=true' >> ~/.bashrc
          source ~/.bashrc
          ```
    - If using express mode:
      - Set the `GOOGLE_API_KEY` environment variables. In the following methods, replace `YOUR_GOOGLE_API_KEY` with your Vertex AI API key provided by express mode:
        - You can temporarily set these environment variables in your current shell session using the following commands:
          ```bash
          export GOOGLE_API_KEY="YOUR_GOOGLE_API_KEY"
          export GOOGLE_GENAI_USE_VERTEXAI=true
          ```
        - For repeated use, you can add the environment variables to your `.env` file (located in the project directory or user home directory) or your shell's configuration file (like `~/.bashrc`, `~/.zshrc`, or `~/.profile`). For example, the following commands adds the environment variables to a `~/.bashrc` file:
          ```bash
          echo 'export GOOGLE_API_KEY="YOUR_GOOGLE_API_KEY"' >> ~/.bashrc
          echo 'export GOOGLE_GENAI_USE_VERTEXAI=true' >> ~/.bashrc
          source ~/.bashrc
          ```
