An error occurred when downloading a background assets packs hosted by Apple.

Question

Created Jul ’25

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On macOS Tahoe26.0, iOS 26.0 (23A5287g), Xcode 26.0 beta 3 (17A5276g) 1、Follow this tutorial Downloading asset packs hosted by Apple When i download a background asset packs hosted by Apple, Xcode callback "Download failed: The helper received an invalid server response with the status code “400”." Before downloading, I uploaded the three aar files to the Apple server using the Transporter app. Three Manifest.json content is： {"assetPackID":"bdassets2","downloadPolicy":{"onDemand":{}},"fileSelectors":[{"file":"1.jpg"},{"file":"2.pag"},{"file":"3.mp4"}],"platforms":["iOS"]} and {"assetPackID":"bdassets1","downloadPolicy":{"prefetch":{"installationEventTypes":["firstInstallation","subsequentUpdate"]}},"fileSelectors":[{"file":"1.jpg"},{"file":"2.pag"},{"file":"3.mp4"},{"directory":"a1"}],"platforms":["iOS"]} and {"assetPackID":"bdassets0","downloadPolicy":{"essential":{"installationEventTypes":["firstInstallation","subsequentUpdate"]}},"fileSelectors":[{"file":"1.jpg"},{"file":"2.pag"},{"file":"3.mp4"},{"directory":"a1"}],"platforms":["iOS"]}

The same error was reported when the three aar files were obtained. I obtained it using the following code: do { let assetPack = try await AssetPackManager.shared.assetPack(withID: "bdassets2") try await AssetPackManager.shared.ensureLocalAvailability(of: assetPack) } catch { print("Download failed:", error) }

2、Follow this tutorial Testing your asset packs locally I use this command line to start the test server：xcrun ba-serve --host 172.17.9.62 bdassets2.aar, The content displayed on the terminal is： Loading asset packs… Loading the asset pack at “bdassets2.aar”… Choose an identity in the panel to continue. Listening on port 56061…

When running the project, Xcode reports an error:Download failed: Could not connect to the server. I use iPhone directly visit this website: https://172.17.9.62:56061, on the page display "Hello, world!"

There are too few error messages in both of the above questions. I have no idea what the specific reasons are.I hope someone can offer some guidance. Best Regards.

Answered by Frameworks Engineer in 849521022

For the first question, Apple-hosted asset packs are currently available only when an app is installed from TestFlight for internal testers (i.e., testers who are members of your development team in App Store Connect). Later this year, they’ll become available in other situations, such as when an app is installed from Xcode or the App Store. Until such time, the HTTP 400 error that you see is expected. In the meantime, you can continue to use the process that’s described in Testing Your Asset Packs Locally as you develop your app in advance of its release on the App Store.

For the second question, we’ll need some additional logging to investigate the problem further. Could you file a feedback report using Feedback Assistant on the device that shows the error and reply to this thread with the feedback ID? That way, we can diagnose the problem and follow up with you via Feedback Assistant. If you’re unfamiliar with the process, then you can learn more about filing feedback with Feedback Assistant. Thanks!

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Answer 1

Frameworks Engineer OP

Apple

Jul ’25

Recommended

For the first question, Apple-hosted asset packs are currently available only when an app is installed from TestFlight for internal testers (i.e., testers who are members of your development team in App Store Connect). Later this year, they’ll become available in other situations, such as when an app is installed from Xcode or the App Store. Until such time, the HTTP 400 error that you see is expected. In the meantime, you can continue to use the process that’s described in Testing Your Asset Packs Locally as you develop your app in advance of its release on the App Store.

For the second question, we’ll need some additional logging to investigate the problem further. Could you file a feedback report using Feedback Assistant on the device that shows the error and reply to this thread with the feedback ID? That way, we can diagnose the problem and follow up with you via Feedback Assistant. If you’re unfamiliar with the process, then you can learn more about filing feedback with Feedback Assistant. Thanks!

1

Answer 2

Frameworks Engineer OP

Apple

Jul ’25

After further investigation, it looks like there’s a bug when saving the URL override’s port number on some test devices. Until this bug is fixed, a workaround is to configure the mock server to serve on port 443 by passing the -p 443 option to ba-serve. By default, in the absence of a custom port number in a URL override, a test device should try to communicate with the mock server over port 443.

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Answer 3

RyanFerrell OP

Jul ’25

-p 443

Thanks for that port set flag. I assume I just need to retrace my steps to find the provisioning mistake along the way:

xcrun ba-serve --host 192.168.0.10 -p 443 pack.aar
xcrun ba-serve url-override https://192.168.0.10
-> on iOS 26.0 b4 device w/ URL Override set

2025-07-26 14:41:39.804 ba-serve[36964:3124040] CFNetwork SSLHandshake failed (-9806)

The certificate for this server is invalid. You might be connecting to a server that is pretending to be “192.168.0.10” which could put your confidential information at risk.

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