Apple-hosted Managed Background Assets fails on macOS 26.6.1 with -1200 / -3007

Hi,

We are seeing Apple-hosted Managed Background Assets download failures on macOS 26.6.1 and would appreciate confirmation of whether this is a known issue or a configuration problem.

Environment

• macOS app using Apple-hosted Managed Background Assets
• Apple Silicon Macs: M1 and M4
• App version: 1.0.2 (build 10)
• App and downloader extension are sandboxed and use the same App Group
• No ba-serve development URL override is configured: xcrun ba-serve url-override reports that no override is set.

Observations

On the same M1 Mac:

• On macOS 26.5.2, Background Assets began transferring an asset pack successfully. The log recorded 136,586,876 bytes received before I manually cancelled the download.
• After upgrading to macOS 26.6.1, Background Assets reaches manifest resolution and download scheduling, but the asset transfer fails.

The macOS 26.6.1 logs show:

NSURLErrorDomain -1200
The certificate for this server is invalid / secure connection failed

kCFStreamErrorDomainSSL -9816
server closed session with no notification

NSURLErrorDomain -3007
Download decoding failed

A separate M4 Mac running macOS 26.6.1 also reproduces the issue.

One relevant variable: both the working 26.5.2 log and the failing 26.6.1 log show the Background Assets traffic passing through a local HTTP/S proxy at 127.0.0.1:6152. I am now testing a direct route for odr.itunes.apple.com and amp-api.apps.apple.com, but this proxy path was also present in the 26.5.2 transfer that started successfully.

The asset pack IDs in the two captured logs are not identical, so this is not a strict same-pack A/B comparison. However, the failure is reproducible for Apple-hosted packs on 26.6.1, while the pre-upgrade log shows a real transfer on the same M1 Mac.

Has anyone seen either of these on macOS 26.6 / 26.6.1?

1. NSURLErrorDomain -3007 (Download decoding failed) for Apple-hosted Background Assets
2. TLS error -1200 / kCFStreamErrorDomainSSL -9816 during a Background Assets pack transfer
3. A change in support or behavior for HTTP/S proxy routing of Apple-hosted asset-pack downloads

I have filed Feedback Assistant report FB24301118 with the relevant logs and diagnostic attachment.

Thanks.