We are experience a similar issue. Feedback assistant bug: FB21235642 What I filed in that bug report: We are seeing installation of our PKGs that have been working for years across multiple OS versions are now failing to install on macOS 26.1. This can be reproduced with the "Chip-Osc Installer Mac.pkg" in the attached Chip-Osc.iso. This issue is happening with hundreds of our ISO/PKG installers; "Chip-Osc" is one with small file size that reproduces the issue. When run with GUI by double-clicking the "Chip-Osc Installer Mac.pkg" in Finder we see the following error message: "The installation failed. The Installer could not install the software. The Installer could not install the software because there was no software found to install." We also see a failure when running from the command line. The following command: sudo installer -pkg /Volumes/Chip-Osc/Chip-Osc\ Installer\ Mac.pkg -target / -verbose Fails with this error: timestamp file successfully generated! installer: Package name is Chip-Osc installer: Upgrading at base path / installer: Preparing for installation…..... 2025-12-02 16:28:26.223 installer[96886:10294062] Opened package is not the same at install time... installer: The upgrade failed. (The Installer could not install the software because there was no software found to install. The Installer could not install the software.) Our issue seems related to the issue described in this developer forum thread: https://developer.apple.com/forums/thread/806222 Like the installers in that thread our PKG installers do bundle and run other PKG installers included in the top level PKG. One other observation is that these installers are not installing executable content.