Installer packages are failing to install on macOS26.1

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.

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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

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.

Hi @roth-izo ,

You have to use productbuild command to create an archive which will bundle all the child packages inside and create a main archive.

productbuild --synthesize --package pkg1 --package pkg2 path/distribution.dist

Once the distribution.dist file is created, you can use following command to create the final package.

productbuild --distribution path/distribution.dist --package-path <path to pkg1, pkg2> --identifier com.xxx.xxx --version xxxx --sign "xxxx --timestamp <path to final>/Package.pkg

In the distribution.dist you can put other restriction you need. Please refer https://developer.apple.com/library/archive/documentation/DeveloperTools/Reference/DistributionDefinitionRef/Chapters/Distribution_XML_Ref.html

regards

Prema Kumar

premak, Thanks for helping out here!

Earlier I wrote:

I recommend that you recheck FB20929578 in a few days time.

I was being deliberately cryptic there because I wanted to see what was officially shared before I made any comments here on the forums. Now that that’s happened, I can talk about the resolution.

FB20929578 was resolved as not to be fixed. It’s unusual for us to ‘break’ existing software products [1] like this, so it’s not something we do lightly. In this case, the motivation for the macOS 26.1 change was to address a security vulnerability.

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

[1] Well, in this case it’s the installer package, not the software itself, but that’s a distinction without a difference.