Set environment variables

A variable you set in your shell lasts for that terminal session, while a variable in a settings file applies every time claude runs.

In your shell

Set the variable before launching claude:

```bash theme=\{null\}
export API_TIMEOUT_MS="1200000"
claude
```

To set it for every session, add the `export` line to `~/.bashrc`, `~/.zshrc`, or your shell's profile file.

```powershell theme=\{null\}
$env:API_TIMEOUT_MS = "1200000"
claude
```

To set it for every session, run `[Environment]::SetEnvironmentVariable("API_TIMEOUT_MS", "1200000", "User")` and open a new terminal.

```batch theme={null}
set API_TIMEOUT_MS=1200000
claude
```

To set it for every session, run `setx API_TIMEOUT_MS "1200000"` and open a new terminal.

The assignment line prints nothing on success, so confirm the variable is set by printing it in the same shell before you run claude:

```bash theme={null}
echo $API_TIMEOUT_MS
```

```powershell theme=\{null\}
echo $env:API_TIMEOUT_MS
```

```batch theme=\{null\}
echo %API_TIMEOUT_MS%
```

In settings files

Add variables under the env key in a settings.json file, creating the file if it doesn't exist. Claude Code reads them directly from the file, so they take effect no matter how claude was launched. A running session applies new and changed values to its environment when you save the file, but a feature that reads its variables once at startup, such as OpenTelemetry monitoring, keeps its startup values until you relaunch. Removing a variable from the file doesn't unset it in a running session; the removal takes effect the next time you launch claude.

{
  "env": {
    "API_TIMEOUT_MS": "1200000",
    "BASH_DEFAULT_TIMEOUT_MS": "300000"
  }
}

The file you choose controls who the variables apply to:

File	Applies to
~/.claude/settings.json	You, in every project
.claude/settings.json	Everyone working in the project, checked into source control
.claude/settings.local.json	You, in this project only, gitignored when Claude Code saves a setting to it; add it to your gitignore if you create it by hand
Managed settings	Everyone in your organization, deployed by an admin

See Settings files for where each file lives and Settings precedence for how they combine when more than one sets the same variable.