Trying to upload an app binary from within Xcode (26.0.1) to Apple's AppStoreConnect, be it either for validation or for distribution, currently fails for me with this error:

This doesn't give a lot of clues, but you can press on "Show Logs" and dig deeper.

In my case, the IDEDistributionPipeline.log file contained these (edited) lines near the bottom:

2025-10-18 13:28:19 +0000  Skipping stripping extended attributes because the codesign step will strip them.
[...]
2025-10-18 13:28:23 +0000  Processing step: IDEDistributionCreateIPAStep
2025-10-18 13:28:23 +0000  Running /usr/bin/rsync '-8aPhhE' [...edited...]
2025-10-18 13:28:23 +0000  rsync: on remote machine: --extended-attributes: unknown option
2025-10-18 13:28:23 +0000  rsync error: syntax or usage error (code 1) at main.c(1455) [server=3.0.9]
2025-10-18 13:28:23 +0000  rsync(34442): error: unexpected end of file
2025-10-18 13:28:23 +0000  /usr/bin/rsync exited with 1
2025-10-18 13:28:23 +0000  Step "<IDEDistributionCreateIPAStep: 0x85f38f2a0>" failed with error "Error Domain=IDEFoundationErrorDomain Code=1 "Copy failed" UserInfo={NSLocalizedDescription=Copy failed}"

So, apparently, the current version of rsync on Apple's server is not a version that supports "extended attributes". Or maybe codesign did not strip the extended attributes as it was told.

Neither is something that I can do much about. Waiting for a fix...

Update 2025-10-19

Apple’s Developer Support for “Binary Delivery and Processing” only offers administrative support and suggests using the forums instead…

Which rsync?

This stackoverflow thread suggests that it might be a wrong local version of rsync, and yes, I have a /usr/local/bin/rsync version that I use for backup scripts; the original /usr/bin/rsync is unchanged:

# rsync --version
rsync  version 3.0.9  protocol version 30
[...]
# /usr/bin/rsync --version
openrsync: protocol version 29
rsync version 2.6.9 compatible

It turns out, if I launch Xcode from the Finder, it works!

But if I launch Xcode via my xcode command-line alias, it inherits my local $PATH settings and uses my custom version of rsync. As a fix, I have updated my alias to cut out all /usr/local paths before opening Xcode:

alias xcode="ls | grep xcodeproj | \
    env PATH=$(echo $PATH|sed 's//usr/local/[^:]*://g') \
    xargs open -a /Applications/Xcode.app"