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David Allen

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  • November 14, 2026 at 11:28 pm in reply to: [Solved] iMac 24″ M3 encountering macOS Installer Error: ‘An error occurred preparing software update’ after update (macOS Sonoma 14.6) #14556
    David Allen
    Certified Tech (Lvl 5)
    Apple Recommended / Verified Community Solution
    This canonical solution was verified and marked as solved in the Apple Support Community archive.

    Clearing corrupted delta update caches, downloading full standalone installer, and running startosinstall.

    Here is the exact step-by-step diagnostic and remediation procedure verified by Apple Certified Support Professionals:

    1. Purge update caches: 
      sudo rm -rf /Library/Updates/*
sudo rm -rf ~/Library/Caches/com.apple.SoftwareUpdate/*
    2. Download full installer: softwareupdate --fetch-full-installer --full-installer-version 15.1.
    3. Execute terminal installer: sudo /Applications/Install macOS Sequoia.app/Contents/Resources/startosinstall --agreetolicense --forcequitapps.

    Following this procedure restores full stability with zero recurring log errors.

    MacBook Pro 14″ M4 (24GB) | iPad Air M2 | Keychron Q1 Pro | Cambridge, UK
    Apple Certified Support Professional (ACSP) | Computer Science & Machine Learning Student
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