hermes - 💡(How to fix) Fix [Bug]: Desktop update fails on macOS with "Backend updated, but the desktop rebuild failed" (EAGAIN in npm ci postinstall)

Description

On macOS, clicking "Update" in the Hermes Desktop app (or running hermes desktop --build-only) triggers npm ci from the repo root to install workspace dependencies. During this install, the postinstall script for electron-winstaller (a Windows-only dependency of electron-builder) spawns a child process via sh -c node ./script/select-7z-arch.js which fails with EAGAIN ("Resource temporarily unavailable").

The same error can also affect agent-browser's postinstall script.

Impact

The npm ci step fails, which causes the desktop GUI rebuild to abort. The user sees:

Backend updated, but the desktop rebuild failed. Restart Hermes to retry.

The Python backend has been updated (git pull + pip install succeeded), but the Electron .app was never rebuilt. The user is stuck in a broken state until they manually rebuild from the terminal.

Root Cause

The npm ci command in _run_npm_install_deterministic (in hermes_cli/main.py) runs all package lifecycle scripts. On macOS, spawning sh from a Node.js postinstall script can hit macOS process resource limits, producing EAGAIN. The failure is deterministic for electron-winstaller because it always tries to run its select-7z-arch.js script on install.

Fix

PR #39845 modifies _run_npm_install_deterministic to detect install-script failures in stderr (by matching patterns like info run, EAGAIN+spawn, ERR!+script) and retry once with --ignore-scripts. This is safe because electron-builder handles native-module rebuilding independently during its own packaging step.

Environment

• macOS (any version)
• Hermes Desktop (any local or source build)
• Node.js via Hermes-managed install

Related

• PR #39845