Installer packages are failing to install on macOS26.1

Hi, We use Flat package installers (.pkg based installers) to install our applications on macOS. In macOS 26.1, installation is failing with the error

Unable to use PK session due to incompatible packages. Terminating. 2025-11-03 14:22:36+05:30 Admin-3 installer[1160]: Install failed: The Installer could not install the software because there was no software found to install.

Same installer package is working on macOS 26.

Any help is greatly appreciated.

Answered by DTS Engineer in 865550022

You should be getting an official response in Feedback Assistant soon. I recommend that you recheck FB20929578 in a few days time.

If that response is insufficiently clear, reply here with your follow-up questions and I’ll see what I can do to clarify things.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Is this only affecting new versions of your product? Or are you seeing it with old versions? That is, if you take a version of your product built, say, 6 months ago and try to install it on macOS 26.0 and macOS 26.1, do you still see it work on the former and fail on the latter?

If so, you should file a bug about that, making sure to include:

  • A copy of the installer package
  • A sysdiagnose log taken shortly after seeing the failure

Once you’re done, please post your bug number.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Hi,

Thank you for the reply.

Yes, it is affecting the older version of the product which was released few months back. New and older version of the product works on macOS 26. Our software was working on beta version of the macOS 26.1 as well.

Bug id is: FB20929578

Regards Prema Kumar

Hi,

Installation was working on build version 25B5042K.

regards

Prema Kumar

Bug id is: FB20929578

Thanks.

I looked at your bug and, while there’s a sysdiagnose and a system profile, I can’t see a copy of your installer package. Did you attach it? If not, please do.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Hi,

In the bug description, I have mentioned a link to download our package.

Please let me if that is not part of the message.

regards

Prema Kumar

Got it. Thanks.

I took a look at your product and it seems that I completely misunderstood the issue here. I was expecting a single installer package (.pkg) but it’s actually a disk image that contains an app and many different installer packages.

Looking again at your bug I believe your app is running the installer tool with the /Volumes/F____C______W__________/OSX/C___W______.pkg package (I’ve blanked out most of the path, but I figured you’d be able to recognise it). Is that right?

I was curious if this was tied to the installer tool or your app’s use of that tool, so I opened that package with the Installer app and tried to install it. It failed in a similar fashion. Does that match your expectations?

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Hi, Thank you for the support.

Yes your understanding is correct. it fails in both the ways.

regards

Prema Kumar

Hi @Quinn,

Do you have any update on this issue?

regards

Prema Kumar

You should be getting an official response in Feedback Assistant soon. I recommend that you recheck FB20929578 in a few days time.

If that response is insufficiently clear, reply here with your follow-up questions and I’ll see what I can do to clarify things.

Share and Enjoy

Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Hi Quinn,

Thank you.

I was planning to use productbuild command to create nested packages. Could you please help on how to call preinstall and postinstall scripts in the packages created using productbuild command?

regards

Prema Kumar

Could you please help on how to call preinstall and postinstall scripts in the packages created using productbuild command?

I’m hardly an installer expert, but my understanding is that:

  1. You pass a components property list path to pkgbuild via the --component-plist argument.
  2. You reference your scripts from there via the BundlePreInstallScriptPath and BundlePostInstallScriptPath properties. See the Component Property List section within the pkgbuild man page.
  3. You then pass that package to productbuild to build the final signed flat package.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Hi Quinn,

Thank you for the support.

I am not able to include the resources folder inside the archive using the --resources option of productbuild command.

Following is the command I am trying.

productbuild --distribution distribution.dist --package-path cont --resources /path/resource --identifier com.abcd --version 7.2.0.01 --sign "Developer ID Installer: xxx" --timestamp test.pkg

There is no error in building. After the build, if I expand the .pkg file, Resources are not included. Could you please help on this?

regards

Prema Kumar

Installer packages are failing to install on macOS26.1
 
 
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