Desktop (Electron) sandbox instances

make dev

+

make start

(Electron) uses

MUX_ROOT

for persisted state (config, sessions, worktrees, etc.). Running multiple Electron instances against the same mux root is noisy and risky during development.

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

MUX_ROOT

.

Quick start

make dev-desktop-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:
  • Vite devserver port (used by the renderer)
  • Electron remote debugging port (optional)
• Runs

  make dev

  with:

  • MUX_ROOT=<temp>

  • MUX_VITE_PORT=<free-port>

• Waits for Vite to be reachable, then runs

  make build-static

  (Electron expects

  dist/splash.html

  )
• Launches Electron (

  bunx electron .

  ) with:

  • MUX_ROOT=<temp>

  • MUX_DEVSERVER_HOST=127.0.0.1

  • MUX_DEVSERVER_PORT=<vite-port>

  • MUX_SERVER_PORT=0

    by default (avoids

    EADDRINUSE

    if your

    config.json

    pins

    apiServerPort

    )

  • CMUX_ALLOW_MULTIPLE_INSTANCES=1

    (so you can run alongside another dev instance)

Options

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

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

# Pin Vite port
VITE_PORT=5174 make dev-desktop-sandbox

# Control how long we wait for Vite to come up (ms)
VITE_READY_TIMEOUT_MS=120000 make dev-desktop-sandbox

# Enable/pin Electron remote debugging port (defaults to an auto-picked free port)
ELECTRON_DEBUG_PORT=9223 make dev-desktop-sandbox

# Disable Electron remote debugging entirely
ELECTRON_DEBUG_PORT=0 make dev-desktop-sandbox

# Override the internal API server port (defaults to 0/random for sandboxes)
MUX_SERVER_PORT=3772 make dev-desktop-sandbox

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

Optional: deeper Electron isolation (

MUX_E2E=1

)

Even with a unique

MUX_ROOT

, Electron's

userData

directory (localStorage, window state, single-instance lock, etc.) is not automatically relocated unless

MUX_E2E=1

is set.

If you want full isolation (including

userData

), run:

MUX_E2E=1 make dev-desktop-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

  .