CLAUDE_EFFORT

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_EFFORT is a Claude Code environment variable: Set thinking effort level at spawn time without the interactive /effort picker. Scriptable effort control: run high effort on the architect agent, low effort on the summarizer, xhigh on the critic — from the same harness without any user interaction. Added between v2.1.128 and v2.1.138 and still present in v2.1.294. It is listed in the official reference.

Status	Present in v2.1.294
Added	Added between v2.1.128 and v2.1.138
Category	Models and thinking
Official docs	Listed

How to set it

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

export CLAUDE_EFFORT=<value>
claude

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

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

Release notes that mention it

Related variables

CLAUDE_CODE_ALWAYS_ENABLE_EFFORT: Force-enable reasoning effort level regardless of other settings.
CLAUDE_CODE_EFFORT_LEVEL: Reasoning effort: low, medium, or high (default).
CLAUDE_CODE_MAX_EFFORT_REMINDER
ANTHROPIC_CUSTOM_MODEL_OPTION
ANTHROPIC_CUSTOM_MODEL_OPTION_DESCRIPTION
ANTHROPIC_CUSTOM_MODEL_OPTION_NAME
ANTHROPIC_CUSTOM_MODEL_OPTION_SUPPORTED_CAPABILITIES
ANTHROPIC_DEFAULT_FABLE_MODEL

Frequently asked questions

What does CLAUDE_EFFORT do?

Set thinking effort level at spawn time without the interactive /effort picker. Scriptable effort control: run high effort on the architect agent, low effort on the summarizer, xhigh on the critic — from the same harness without any user interaction.

Which Claude Code version has CLAUDE_EFFORT?

Added between v2.1.128 and v2.1.138 and still present in v2.1.294.

How do I set CLAUDE_EFFORT?

Export it before starting Claude Code (export CLAUDE_EFFORT=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.