Claude Code Needs the Right Environment Before Launch

Claude Code inherits settings from its parent process

Environment variables are named values that applications read when they start. For Claude Code, they can supply credentials, choose an API destination, or adjust behavior without changing your project. The important beginner lesson is simple: a setting must reach the process running Claude Code. Saving a value somewhere does not automatically make it available everywhere.

A terminal usually passes its environment to applications launched inside it. An editor can do the same for its integrated terminal. If either application was already open when you changed a persistent setting, it may still hold the old value. Restarting the relevant terminal or editor is often the missing step.

Authentication and destination settings serve different purposes here

ANTHROPIC_API_KEY supplies an API key for key-based authentication. ANTHROPIC_AUTH_TOKEN supplies a token used for bearer authentication. These are different authentication mechanisms, not interchangeable labels. Follow the instructions for your chosen service rather than setting both and hoping Claude Code chooses correctly.

ANTHROPIC_BASE_URL changes the API destination. It does not provide authentication or guarantee that the destination supports Claude Code. A compatible endpoint must also handle the API behavior Claude Code requires. Use the service’s Claude Code instructions for the exact destination and authentication method.

Before changing anything, decide whether you intend to use Claude Code’s account-based sign-in or API credentials. Existing credentials can affect the authentication path. Avoid mixing several methods while troubleshooting, and remember that API usage may be billed separately from a consumer subscription.

Windows offers persistent settings through user environment controls

On Windows, search the system settings for environment variables and open the environment-variable controls. For a personal setup, add the required names and values under your user variables. System variables have broader scope and generally are unnecessary for one person’s Claude Code installation.

Save the changes, then open a new terminal and launch Claude Code from it. If you work inside an editor, restart the editor too. A temporary value set within PowerShell applies to that session and processes it launches; it does not automatically become a persistent user setting.

If you run Claude Code inside Windows Subsystem for Linux, treat that Linux environment as its own setup. Do not assume values configured in Windows will arrive there exactly as intended.

macOS and Linux depend on shell startup behavior

On macOS and Linux, a temporary environment change normally belongs to the current shell session. For persistence, users commonly place shell-appropriate variable assignments in a startup file read by their shell. The correct location depends on the shell and whether it starts as a login or interactive session.

Check which shell you actually use before following instructions. Many macOS installations use Zsh, while Linux installations vary. Instructions written for Bash are not automatically suitable for every shell. After saving a persistent change, open a fresh terminal and start Claude Code there.

Applications launched from a desktop interface may receive a different environment from terminal-launched applications. If Claude Code works in one place but not another, compare their launch contexts before replacing credentials.

Relay credentials still require careful destination checks

BestRelay, which publishes this article, is a quality-first API relay that forwards each request to the official model named in it, without substitution. Its coverage includes Claude, GPT, Gemini, DeepSeek, Kimi, GLM, Qwen, Grok, and more. It works with Claude Code, Codex, Gemini CLI, and any OpenAI SDK, but each client still needs its appropriate connection settings.

Create a BestRelay account when you are ready to try it. Billing is pay-as-you-go using provider-reported token counts, with cache reads and writes priced separately. Members also earn a referral commission when people they invite top up.

Small verification steps prevent confusing credential failures

Keep credentials out of source control, shared screenshots, and support messages. Verify that required variables exist without printing their secret values. Check for accidental spaces, stale settings, and conflicting authentication variables. Test with a small request, confirm the intended destination and billing account, and rotate any credential that has been exposed.