Multiple list.manifest.json files when building on remote nodes.

[efimovee]

I'm using docker buildx to build multi-arch images on remote nodes.
Here is how:

docker buildx create --name remote-ssh-builder --driver docker-container ssh://user@xx.xx.xx.xx
docker buildx create --name remote-ssh-builder --append --driver docker-container ssh://user@yy.yy.yy.yy
docker buildx build --builder='remote-ssh-builder'  --platform linux/amd64,linux/arm64 \
--provenance=false --sbom=false --no-cache --pull --push \
--tag repo.artifactory.company.com/repo/artifactory-docker-test:latest  -f ./Dockerfile .
 => [internal] load build definition from Dockerfile
 => => transferring dockerfile: 151B
 => [internal] load build definition from Dockerfile
 => => transferring dockerfile: 151B
 => [internal] load .dockerignore
 => => transferring context: 2B
 => [internal] load .dockerignore
 => => transferring context: 2B
 => CACHED [linux/arm64 1/1] COPY some.file /
 => [linux/arm64 1/1] COPY some.file /
 => exporting to image
 => => exporting layers
 => => exporting manifest sha256:f47b2d6b9f54a5b7050c822e678b50fe29dd1a3b67a6a65ad2c24c8f497973d4
 => => exporting config sha256:8f7d3d6c370fa4afa9900d17a78f1343d1fccdfc2925a574faa15ac6411ee622
 => => exporting manifest list sha256:7aa7aa8bbdb612f7cda0a174a9e7c66ac3af52e80893581c4657037ab036efec
 => => pushing layers
 => => pushing manifest for repo.artifactory.company.com/repo/artifactory-docker-test
 => exporting to image
 => => exporting layers
 => => exporting manifest sha256:0303a32135a7addfb1fd8eb843423b17a5c13ec7661dd24eaa616fb502cb612e
 => => exporting config sha256:f3d399a5c659750b99b176ed40624f182b354273a38346117e2e9e25a4a476a8
 => => exporting manifest list sha256:7395f0353190133995592a940a74b1ae9dac2c75e51855549c1a2ea793e73d95
 => => pushing layers
 => => pushing manifest for repo.artifactory.company.com/repo/artifactory-docker-test
 => [auth] repo/artifactory-docker-test:pull,push token for repo.artifactory.company.com
 => [auth] repo/artifactory-docker-test:pull,push token for repo.artifactory.company.com
 => merging manifest list repo.artifactory.company.com/repo/artifactory-docker-test:latest

As a result, I have 3 list.manifest.json in Artifactory:

1. sha256:7aa7aa8bbdb612f7cda0a174a9e7c66ac3af52e80893581c4657037ab036efec
2. sha256:7395f0353190133995592a940a74b1ae9dac2c75e51855549c1a2ea793e73d95
3. merging manifest list repo.artifactory.company.com/repo/artifactory-docker-test:latest

Build attestations is disabled: --provenance=false --sbom=false

When I build it locally (without --builder='remote-ssh-builder') it creates only one list.manifest.json, as expected.

docker buildx build --platform linux/amd64,linux/arm64 \
--provenance=false --sbom=false --no-cache --pull --push \
--tag repo.artifactory.company.com/repo/artifactory-docker-test:latest  -f ./Dockerfile .
 => [internal] load build definition from Dockerfile
 => => transferring dockerfile: 151B
 => [internal] load .dockerignore
 => => transferring context: 2B
 => CACHED [linux/arm64 1/1] COPY some.file /
 => [linux/arm64 1/1] COPY some.file /
 => exporting to image
 => => exporting layers
 => => exporting manifest sha256:01d74111dd064f938eaf8a7ea1cbaed67f65645bb1c5017f859497bc1636039a
 => => exporting config sha256:e4819095c066934bdcd9b6ca210949cfe8bb01bac4f07fc832e1375771389631
 => => exporting manifest sha256:cbb352e54c00de85b278dc0e9f174755fd290448528f7a57accf24328b4a14a3
 => => exporting config sha256:165ca6da5b9a8a9cf51b9a8f3e571f045d5f8c7ae4a8e98e534ff71ece5c987b
 => => exporting manifest list sha256:fbeb03e1f068d236f42066d21fd7b5a9c1efbd3baf04f39caafa75705c345048
 => => pushing layers
 => => pushing manifest for repo.artifactory.company.com/repo/artifactory-docker-test:latest@sha256:fbeb03e1f068d236f42066d21fd7b5a9c1efbd3baf04f39caafa75705c345048
 => [auth] repo/artifactory-docker-test:pull,push token for repo.artifactory.company.com

The question is, why does it push these 2 extra manifest lists from remote nodes? Is it expected behaviour? Is it documented (I couldn't find it)?
Why I ask: presumably, these extra list.manifest.json prevent Artifactory from removing unreferenced daughter-images when the main list.manifest.json is removed/overwritten.

Thanks