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Thomas Scholz

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  • November 15, 2026 at 12:23 am in reply to: [Solved] macOS Installer Error: ‘An error occurred preparing software update’ on macOS Sonoma 14.6: Diagnostic steps and permanent fix #15457
    Thomas Scholz
    Community Contributor
    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.

    iMac 24″ M3 (16GB) | AST 2 Diagnostic Station | ESD Workstation | Munich, DE
    Apple Certified Support Professional (ACSP) | Apple Certified Service Technician (ACiT / ACSP)
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