Fix Xcode 10 Simulator Launch Issue on macOS Mojave by Reinstalling Plug‑Ins

After upgrading to macOS Mojave and enabling Dark Mode, the author found that Xcode 10 could not launch apps on the iOS simulator: the simulator would start but the app remained stuck in the Launching state, eventually showing errors like Failed to initiate service connection to simulator and DTServiceHubClient failed to bless service hub for simulator .

The solution consists of four main steps:

In Finder, locate the Xcode application (usually /Applications/Xcode.app ), right‑click and choose “Show Package Contents”.

Navigate to Contents/PlugIns and make a backup of the entire folder.

Delete the original PlugIns folder and restart Xcode (the app may not start at first).

Restore the backed‑up PlugIns folder to its original location and restart Xcode again.

After completing these steps the simulator works normally. The author notes that the problem reappears after a full system reboot, but the same procedure fixes it each time, suggesting a Mojave‑specific bug.

Additional troubleshooting ideas include:

Checking the Xcode scheme configuration by selecting edit scheme and ensuring the settings are correct.

Resetting the simulator with the “Erase All Content and Settings” command ( erase all content and settings ).

These extra steps are illustrated with screenshots in the original article. The author also mentions that no third‑party Xcode plug‑ins were found in ~/Library/Developer/Xcode/Plug‑ins , confirming the issue lies with the built‑in plug‑ins.

In summary, the only reliable fix for the Xcode 10 + Mojave simulator launch problem is to temporarily remove and then restore Xcode’s own plug‑ins, optionally combined with scheme checks and a simulator reset.