CLAUDE_CODE_EAGER_FLUSH

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_CODE_EAGER_FLUSH is a Claude Code environment variable: Eagerly flush output buffers. 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	Other
Official docs	Not listed

How to set it

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

export CLAUDE_CODE_EAGER_FLUSH=<value>
claude

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

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

Related variables

ANTHROPIC_BETAS: Comma-separated beta feature headers.
ANTHROPIC_CUSTOM_HEADERS: Custom HTTP headers (newline-separated Key: Value).
ANTHROPIC_FEDERATION_RULE_ID
ANTHROPIC_ORGANIZATION_ID
ANTHROPIC_WORKSPACE_ID
BETA_TRACING_ENDPOINT: Custom endpoint for beta tracing.
CLAUDE_AFK_COUNTDOWN_MS
CLAUDE_AI_ORIGIN: Overrides the base URL for Claude AI authentication endpoints.

Frequently asked questions

What does CLAUDE_CODE_EAGER_FLUSH do?

Eagerly flush output buffers

Which Claude Code version has CLAUDE_CODE_EAGER_FLUSH?

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

How do I set CLAUDE_CODE_EAGER_FLUSH?

Export it before starting Claude Code (export CLAUDE_CODE_EAGER_FLUSH=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.