Strip Claudecode Env For Nested Spawn

Strip CLAUDECODE env before spawning Claude SDK subprocess

When to use

• You're building tooling (CLI, dev harness, test runner) that sometimes runs inside a Claude Code / Agent SDK session and spawns a server that ALSO uses the Claude Agent SDK.
• The child process silently refuses to start, or the SDK throws an obscure "nesting detected" error.

How it works

The Claude Agent SDK sets CLAUDECODE=1 in its subprocess env. A nesting guard inside the SDK checks for this var and refuses to run to prevent infinite spawn loops. When you legitimately need to run an SDK subprocess from within an SDK session (e.g. bun run scripts/server.ts from Claude Code running a CLI), strip the var before spawn:

const { CLAUDECODE: _drop, ...parentEnv } = process.env;
spawn([...], { env: { ...parentEnv, /* your overrides */ } });

Example

// apps/cli/src/server-spawner.ts
const { CLAUDECODE: _, ...parentEnv } = process.env;
const proc = Bun.spawn(['bun', 'run', serverEntry], {
  env: {
    ...parentEnv,
    CRAFT_SERVER_TOKEN: token,
    CRAFT_RPC_PORT: '0',
  },
  stdout: 'pipe',
  stderr: 'pipe',
});

Gotchas

• You may also need to strip CLAUDE_CODE_SSE_PORT, CLAUDE_CODE_OAUTH_TOKEN, or other CLAUDE_* vars depending on SDK version - check SDK release notes.
• Don't blindly copy all env - the parent's CRAFT_SERVER_URL or debug flags may be inappropriate for the child.
• This is NOT a security-relevant strip (the guard is for loop prevention); the token is still the real auth boundary.
• After stripping, test both code paths: inside and outside a Claude session. Tests that only pass in one are a trap.
• Document why you're doing it - a comment saves the next maintainer an hour.

Source: kjuhwa/skills-hub — distributed by TomeVault.