CLAUDE_CODE_SYSTEM_PROMPT_GB_FEATURE

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_CODE_SYSTEM_PROMPT_GB_FEATURE is a Claude Code environment variable: Names a GrowthBook feature flag whose value overrides the system prompt — but only when CLAUDE_CODE_REMOTE is set. Anthropic can A/B-test remote-session prompts without shipping new binaries while local sessions stay stable. Added between v2.1.108 and v2.1.114 and still present in v2.1.294. 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_SYSTEM_PROMPT_GB_FEATURE=<value>
claude

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

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

Release notes that mention it

• Claude Code v2.1.114 — Native Binary Launcher, /fewer-permission-prompts, and 20 New Environment Variables

Related variables

• 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_MID_CONVERSATION_SYSTEM: Inject a system message mid-conversation.
• CLAUDE_CODE_PROMPT_CACHE_TTL
• CLAUDE_CODE_VERIFY_PROMPT: The verify flow was reworked; the standalone prompt override no longer maps to how verification runs.
• CLAUDE_CODE_APPEND_PROMPT_HEAD
• CLAUDE_CODE_HOST_PROMPT_SUPERSEDES_RECORD
• CLAUDE_CODE_MORNING_BRIEF_PROMPT
• CLAUDE_CODE_REMOVE_PROMPT_STRINGS

Frequently asked questions

All variables, searchable: Claude Code environment variables.