CLAUDE_CODE_SUBAGENT_EFFORT

Updated October 31, 2026 by Alex Sorokoletov

CLAUDE_CODE_SUBAGENT_EFFORT is a Claude Code environment variable: Sets the effort level subagents run at when their own definition names none. Read when a subagent leaves effort unset, it takes a level (low, medium, high, xhigh) or inherit. Added in v2.1.315 and still present in v2.1.315. 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_SUBAGENT_EFFORT=<value>
claude

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

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

Release notes that mention it

• Claude Code Version Tracker: Undocumented Env Vars, Feature Gates & Models
• claude-code-env-vars-v2-1-315

Related variables

• CLAUDE_CODE_ENABLE_APPEND_SUBAGENT_PROMPT: Authorizes SDK callers to append a custom string to a subagent's system prompt via options.appendSubagentSystemPrompt.
• CLAUDE_CODE_FORK_SUBAGENT: Changelog-confirmed[1]: set to 1 to run subagents as forked processes (v2.1.117 on external builds, v2.1.121 extended to non-interactive SDK/-p sessions).
• CLAUDE_CODE_FORWARD_SUBAGENT_TEXT: Includes subagent text and thinking in stream-json output, paired with a new --forward-subagent-text flag.
• CLAUDE_CODE_MAX_SUBAGENT_SPAWN_DEPTH: Nesting-depth cap on delegation, default 1 — subagents no longer spawn their own subagents, and the team roster stays flat.
• CLAUDE_CODE_MEMORY_SUBAGENT_APPEND: When set, the memory block is not appended to a subagent's system prompt; by default a subagent includes that memory in its prompt.
• CLAUDE_CODE_SUBAGENT_CONFIG_WARNING: Set to a truthy value to enable the subagent configuration warning or a falsy value to disable it, overriding the server default.
• CLAUDE_CODE_SUBAGENT_HISTORY: Gates a subagent history view; when unset the view falls back to the tengu_rustling_crescent feature gate, which is off by default.
• CLAUDE_CODE_SUBAGENT_MODEL: Force a specific model for sub-agent operations.

Frequently asked questions

All variables, searchable: Claude Code environment variables.