Apple managed asset pack for FoundationModels adapter on Testflight does not download (statusUpdates silent)

Hi,

I'm stuck distributing a custom FoundationModels adapter as an Apple-hosted managed asset pack via TestFlight.

Everything looks correctly configured end to end but the download just never starts and the statusUpdates sequence is silent.

Here's my configuration:

1. App Info.plist:

<key>BAHasManagedAssetPacks</key><true/>
<key>BAUsesAppleHosting</key><true/>
<key>BAAppGroupID</key><string>group.com.fiuto.shared</string>

Entitlement com.apple.developer.foundation-model-adapter on both the app and the asset downloader extension. The asset downloader extension uses StoreDownloaderExtension , returning SystemLanguageModel.Adapter.isCompatible(assetPack) from shouldDownload , and the app group on app and asset download extension is the same.

I have exported the adapter with toolkit 26.0.0, obtaining: adapterIdentifier = fmadapter-FiutoAdapter-1234567

I have packaged the asset pack using xcrun ba-package and uploaded it to App Store Connect via Transporter, and I get the "ready for internal and external testing" state on App Store Connect, and I have uploaded my app build on TestFlight after the asset pack was marked as ready.

I used this code:

let adapter = try SystemLanguageModel.Adapter(name: "FiutoAdapter")

let ids = SystemLanguageModel.Adapter.compatibleAdapterIdentifiers(name: "FiutoAdapter")
// ids == ["fmadapter-FiutoAdapter-1234567"]

for await status in AssetPackManager.shared.statusUpdates(forAssetPackWithID: ids.first!) {

}

I expect the download to start and the stream to yield first .began, then .downloading(progress) and .finished.

Actually, compatibleAdapterIdentifiers returns the correct ID, the stream is correctly acquired but i get zero events, so no .began/.downloading/.failed/.finished.

Important things:

• 1. I don't get any error in Console as well;
• I tested this as an internal tester on TestFlight
• Tested on iPhone 16 Pro, running iOS 26.3.1 - more than 50GB of free space
• Apple Intelligence is enabled and set in Italian
• Background downloads are enabled.

I've already checked if the adapter identifier matches regex fmadapter-\w+-\w+ , i tried to reinstall the build, rebooting the device, reupload the asset pack, and also checked that the foundation models adapter entitlement is present on both targets.

Is there a known way to diagnose why statusUpdates is silent (no log subsystem seems to show why) in this exact configuration?

Is there maybe any delay between asset pack approval on App Store Connect and availability to TestFlight internal testers that I do not know of?

I've checked other threads for applicable solutions and I've found that this is similar to the symptom reported in this thread: https://developer.apple.com/forums/thread/805140 / (FB20865802) and also i'm internal tester and on stable iOS 26.3.1, so the limitations from this thread: https://developer.apple.com/forums/thread/793565 shouldn't apply.

Thanks