Workers fail with "Claude Code cannot be launched inside another Claude Code session" (CLAUDECODE env var)

[RedcoatAsher]

Problem

Starting with Claude Code v2.1.71+, launching subtask send from within a Claude Code session fails immediately with:

Error: Claude Code cannot be launched inside another Claude Code session.
Nested sessions share runtime resources and will crash all active sessions.

Root Cause

Claude Code now sets CLAUDECODE=1 in its process environment. When subtask spawns a worker (which runs claude), the child process inherits this env var and hits the nesting guard:

if (process.env.CLAUDECODE && !process.argv.includes("--team-name")) {
  // prints error and exits
}

Workaround

Clearing the env var before spawning the worker process works:

CLAUDECODE="" subtask send <task> "prompt"

Suggested Fix

When subtask spawns worker processes, explicitly unset CLAUDECODE from the child process environment:

const env = { ...process.env };
delete env.CLAUDECODE;
// spawn worker with this env

Context

• Claude Code version: 2.1.71+
• The --team-name flag is an internal exception used by Claude's own agent teams feature
• Related: Nested session check blocks non-interactive subcommands like claude plugin validate anthropics/claude-code#25803, Bug: Subprocess inherits CLAUDECODE=1 env var, preventing SDK usage from Claude Code hooks/plugins anthropics/claude-agent-sdk-python#573

Environment

• macOS (Darwin 25.3.0)
• Node.js
• subtask latest (installed via skill)