run-ios: "Unable to boot device in current state: Booted" alert when the simulator is already booted #2820

Environment

• @react-native-community/cli: 20.2.0 (also reproduces on main, latest commit 9013a48 at time of writing)
• OS: macOS (Apple Silicon)
• Xcode: stable (not Xcode 27 beta) — Simulator.app present at $(xcode-select -p)/Applications/Simulator.app, so the run-ios code path takes the Simulator.app branch (not the DeviceHub branch added in feat: Support DeviceHub for Xcode 27+ #2806 )

Description

Running run-ios against a simulator that is already booted pops a modal alert from Simulator.app reading:

Unable to boot device in current state: Booted

before the build proceeds. The alert must be dismissed manually and it recurs on every re-launch until the simulator is shut down. The build itself still succeeds. A cold first launch (no booted device) is unaffected.

Root cause

In packages/cli-platform-apple/src/commands/runCommand/runOnSimulator.ts, the open Simulator.app --args -CurrentDeviceUDID <udid> call runs unconditionally, before the simulator.state !== 'Booted' guard:

if (fs.existsSync(simulatorApp)) {
 child_process.execFileSync('open', [
 simulatorApp,
 '--args',
 '-CurrentDeviceUDID',
 simulator.udid,
 ]);
} else if (fs.existsSync(deviceHubApp)) {
 ...
}
if (simulator.state !== 'Booted') {
 bootSimulator(simulator);
}

Passing -CurrentDeviceUDID for an already-booted device makes Simulator.app re-attempt a boot of that device, which CoreSimulator rejects with the exact string Unable to boot device in current state: Booted. Simulator.app surfaces that rejection as a modal alert.

The later simulator.state !== 'Booted' guard correctly skips the explicit xcrun simctl boot, but it is too late — the open ... --args -CurrentDeviceUDID call has already provoked the dialog. The DeviceHub branch (Xcode 27+) is unaffected, since it never passes -CurrentDeviceUDID.

Fix

Only pass -CurrentDeviceUDID when the device is not already booted; when it is booted, just bring the running Simulator.app to the foreground. A PR is incoming.

Reproducible Demo

1. npx react-native run-ios — boots a fresh simulator; no alert.
2. Leave the simulator booted (don't shut it down).
3. npx react-native run-ios again → the "Unable to boot device in current state: Booted" modal appears over Simulator.app.
4. Click OK to dismiss; the build continues normally.
5. Reproduces on every subsequent run-ios until the simulator is shut down.

Expected: Step 3 should just foreground Simulator.app and install/launch the app — no alert — same as the clean first launch.