preview_start fails with EPERM: uv_cwd on macOS

Bug Description

preview_start consistently fails with EPERM: operation not permitted, uv_cwd when attempting to start a dev server. The subprocess spawned by the preview tool cannot resolve its working directory, even though the CWD is valid and accessible from the shell.

Environment

• OS: macOS (Darwin 25.2.0)
• Node.js: v22.17.0 (via nvm)
• Claude Code: latest (CLI)
• Shell: zsh

Steps to Reproduce

1. Navigate to a Next.js project directory
2. Ensure .claude/launch.json exists with a valid config:

``json
{
"version": "0.0.1",
"configurations": [
{
"name": "dev",
"runtimeExecutable": "npx",
"runtimeArgs": ["next", "dev"],
"port": 3000,
"autoPort": true
}
]
}
``

1. Use preview_start with name: "dev"

Expected Behavior

The dev server starts and preview tools become available.

Actual Behavior

The subprocess immediately crashes with:

Error: EPERM: operation not permitted, uv_cwd
    at process.wrappedCwd [as cwd] (node:internal/bootstrap/switches/does_own_process_state:142:28)
    ...

Troubleshooting Done

• Verified CWD exists and is accessible (pwd, ls -la both work)
• Verified npx is available and functional (which npx, npx --version)
• Tried using node_modules/.bin/next directly instead of npx — same error
• The error occurs before any project code runs — Node.js itself cannot call process.cwd() in the spawned subprocess
• Running npx next dev directly from the same shell works fine

Analysis

The issue appears to be in how the preview infrastructure spawns child processes. The subprocess inherits a CWD context that is stale or has restricted permissions, even though the parent process's CWD is valid. This is a process-management issue in the preview tool, not a project configuration problem.