CLAUDE_CODE_DISABLE_FAST_MODE

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_CODE_DISABLE_FAST_MODE is a Claude Code environment variable: Disable the /fast toggle that uses the same model with faster output. Present since v2.1.69 or earlier and still present in v2.1.294. It is listed in the official reference.

How to set it

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

export CLAUDE_CODE_DISABLE_FAST_MODE=<value>
claude

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

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

Release notes that mention it

• 165 Environment Variables in Claude Code 2.1.69 — What Changed in 50 Versions

Related variables

• CLAUDE_CODE_ENABLE_OPUS_4_7_FAST_MODE
• CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE: Pin Fast mode to Opus 4.6.
• CLAUDE_CODE_SKIP_FAST_MODE_NETWORK_ERRORS: Controls whether Claude Code suppresses or bypasses network errors that occur specifically in fast mode.
• CLAUDE_CODE_SKIP_FAST_MODE_ORG_CHECK: Disables the organization-level eligibility check for fast mode.
• ANTHROPIC_SMALL_FAST_MODEL: Override small/fast model for quick operations.
• CLAUDE_CODE_AUTO_MODE_MODEL: Picks the model that classifies each proposed edit — deliberately separate from the model doing the work.
• CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING: Disable adaptive thinking mode.
• CLAUDE_CODE_DISABLE_LEGACY_MODEL_REMAP

Frequently asked questions

All variables, searchable: Claude Code environment variables.