CLAUDE_CODE_API_KEY_FILE_DESCRIPTOR

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_CODE_API_KEY_FILE_DESCRIPTOR is a Claude Code environment variable: File descriptor to read API key from. Present since v2.1.69 or earlier and still present in v2.1.294. It is not in the official reference.

Status	Present in v2.1.294
Added	Present since v2.1.69 or earlier
Category	Authentication
Official docs	Not listed

How to set it

For one session, export it in the shell that starts Claude Code:

export CLAUDE_CODE_API_KEY_FILE_DESCRIPTOR=<value>
claude

To apply it to every session, add it to the env object of a settings file:

// ~/.claude/settings.json
{
  "env": {
    "CLAUDE_CODE_API_KEY_FILE_DESCRIPTOR": "<value>"
  }
}

Release notes that mention it

83 Undocumented Claude Code Environment Variables (v2.1.19)

Related variables

ANTHROPIC_API_KEY: Primary API key for Claude API.
CLAUDE_CODE_API_KEY_HELPER_TTL_MS: Cache TTL for API key helper.
CLAUDE_CODE_OAUTH_TOKEN_FILE_DESCRIPTOR: File descriptor to read OAuth token from.
CLAUDE_CODE_WEBSOCKET_AUTH_FILE_DESCRIPTOR: File descriptor for WebSocket credentials.
CLAUDE_CODE_GATEWAY_TOKEN_FILE_DESCRIPTOR
CLAUDE_CODE_CLIENT_KEY: Path to client private key.
CLAUDE_CODE_CLIENT_KEY_PASSPHRASE: Passphrase for encrypted client key.
CLAUDE_CODE_FILE_READ_MAX_OUTPUT_TOKENS: Max tokens for file read output.

Frequently asked questions

What does CLAUDE_CODE_API_KEY_FILE_DESCRIPTOR do?

File descriptor to read API key from

Which Claude Code version has CLAUDE_CODE_API_KEY_FILE_DESCRIPTOR?

Present since v2.1.69 or earlier and still present in v2.1.294.

How do I set CLAUDE_CODE_API_KEY_FILE_DESCRIPTOR?

Export it before starting Claude Code (export CLAUDE_CODE_API_KEY_FILE_DESCRIPTOR=value), or add it to the "env" object in ~/.claude/settings.json to apply it to every session.

All variables, searchable: Claude Code environment variables.