I can't speak for CUE, but I've worked with CI and "build orchestration tools"in the past. Most CI providers provide executor APIs that let you override it as a plugin. One example is https://buildkite.com/resources/plugins/buildkite-plugins/do... - you mark this as "this is using docker" and configure it in the environment, and then you provide the command. You need to be very careful about the design of the plugin, but I've done it a few times and it's viable.