CLAUDE_CODE_DROP_UNAVAILABLE_DEFERRED_TOOL

Updated November 6, 2026 by Alex Sorokoletov

CLAUDE_CODE_DROP_UNAVAILABLE_DEFERRED_TOOL is a Claude Code environment variable: When true, a deferred tool that becomes unavailable is dropped rather than kept registered while it is gone. Added in v2.1.319 and still present in v2.1.319. 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_DROP_UNAVAILABLE_DEFERRED_TOOL=<value>
claude

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

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

Related variables

• CLAUDE_CODE_DISABLE_ADVISOR_TOOL: Disables what appears to be an internal advisory tool.
• CLAUDE_CODE_EMIT_TOOL_USE_SUMMARIES: Emit tool use summary events.
• CLAUDE_CODE_ENABLE_EXPERIMENTAL_ADVISOR_TOOL: Enables the experimental Advisor Tool — a server-side tool with its own advisorModel config option.
• CLAUDE_CODE_MAX_TOOL_USE_CONCURRENCY: Max concurrent tool executions; default 10.
• CLAUDE_CODE_PEWTER_OWL_TOOL: When set to true, it can stop certain tool results from ending the agent's turn, so the agent keeps going instead of returning control to the user.
• CLAUDE_CODE_TOOL_MEMORY_CGROUP_EXCLUDE
• CLAUDE_CODE_TOOL_MEMORY_LIMIT: Caps memory for Bash tool commands via a Linux/WSL cgroup so a runaway build cannot stall the session.
• CLAUDE_CODE_TRANSCRIPT_SLIM_TOOL_RESULTS: In non-interactive SDK sessions, stores tool results in the transcript in a slimmed-down form instead of the counted form when set.

Frequently asked questions

All variables, searchable: Claude Code environment variables.