There's some hacky looking code in AbstrDockerCmdExec.registryConfigs() that uses the dockerClientConfig version to decide whether or not to wrap the X-Registry-Config header base64 encoded json in a 'configs' subobject or not. If the version is greater or equal to v1.19, it doesn't wrap, otherwise, it does. Apparently, the v1.19 remote api is being used as a proxy for whether or not the registry api is v2 or v1, and the v2 api doesn't want the 'configs' wrapper.

However, the default remote api version for the library is UNKNOWN_VERSION, and so this fails 'out of the box' when you have a v2 registry. You have to explicitly set the remote api version to some v1.19+ value for things to work. If docker-java is several layers down the software stack from you, this is a royal pain.