name: dev-server-sandbox description: Run multiple isolated mux dev-server instances (temp MUX_ROOT + free ports)

dev-server sandbox instances

make dev-server starts the mux backend server, which uses a lockfile at:

• <MUX_ROOT>/server.lock (defaults to ~/.mux-dev/server.lock in development)

This means you can only run one dev server per mux root directory.

This skill documents the repo workflow for starting multiple dev-server instances in parallel (including from different git worktrees) by giving each instance its own temporary MUX_ROOT.

Quick start

make dev-server-sandbox

What it does

• Creates a fresh temporary MUX_ROOT directory
• Copies these files into the sandbox if present:
  • providers.jsonc (provider config)
  • config.json (project list)
• Picks free ports (BACKEND_PORT, VITE_PORT)
• Allows all hosts (VITE_ALLOWED_HOSTS=all) so it works behind port-forwarding domains
• Runs make dev-server with those env overrides

Options

# Use a specific root to seed from (defaults to ~/.mux-dev then ~/.mux)
SEED_MUX_ROOT=~/.mux-dev make dev-server-sandbox

# Keep the sandbox root directory after exit (useful for debugging)
KEEP_SANDBOX=1 make dev-server-sandbox

# Pin ports (must be different)
BACKEND_PORT=3001 VITE_PORT=5174 make dev-server-sandbox

# Override which make binary to use
MAKE=gmake make dev-server-sandbox

Security notes

• providers.jsonc may contain API keys.
• The sandbox root directory is created on disk (usually under your system temp dir).
• This flow intentionally does not copy secrets.json.