Ping @scottwittenburg. After #19209 my CI script constantly uploads all binaries, even if they were downloaded from the same binary cache. My CI scripts ends with:

spack buildcache check --rebuild-on-error --mirror-url s3://spack -s /[some_hash]

if [ $? -eq 1 ]; then
    spack buildcache create -af --mirror-url s3://spack --only=package /[some_hash]
fi

and currently it always uploads everything, saying

==> Rebuilding [spec]/[some_hash], reason: full_hash was missing from remote spec.yaml

I've reran the CI job a couple times, and it will always download binaries from cache, build nothing from sources, and subsequently push everything redundantly to the binary cache again.

Indeed when downloading the spec.yaml files I don't see any full_hash entries.

When the user does not require a full hash match, I would expect buildcache check to ignore missing full_hashes on the remote.

Edit, I'll just try to add --require-full-hash-match to my CI-script and the problem should be gone.