CLAUDE_CODE_APPEND_PROMPT_HEAD

Updated October 14, 2026 by Alex Sorokoletov

CLAUDE_CODE_APPEND_PROMPT_HEAD is a Claude Code environment variable. Added in v2.1.284 and still present in v2.1.295. It is not in the official reference.

How to set it

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

export CLAUDE_CODE_APPEND_PROMPT_HEAD=<value>
claude

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

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

Related variables

• CLAUDE_CODE_PROMPT_CACHE_TTL
• CLAUDE_CODE_SIMPLE_SYSTEM_PROMPT: Switches to a reduced system prompt, stripping out the non-essential guidance sections that bulk up the default prompt.
• CLAUDE_CODE_SYSTEM_PROMPT_GB_FEATURE: Names a GrowthBook feature flag whose value overrides the system prompt — but only when CLAUDE_CODE_REMOTE is set.
• CLAUDE_CODE_VERIFY_PROMPT: The verify flow was reworked; the standalone prompt override no longer maps to how verification runs.
• CLAUDE_CODE_HOST_PROMPT_SUPERSEDES_RECORD
• CLAUDE_CODE_MORNING_BRIEF_PROMPT
• CLAUDE_CODE_REMOVE_PROMPT_STRINGS
• ANTHROPIC_BETAS: Comma-separated beta feature headers.

Frequently asked questions

All variables, searchable: Claude Code environment variables.