Stencil v2.12 has been released with several improvements, including updates to the Stencil CLI, testing implementations, and error callstacks. A notable change involves the deprecation of the dist-custom-elements-bundle output target in favor of the dist-custom-elements target, with a CLI warning now alerting users of this upcoming change. The release also includes a bug fix related to the Node.contains method, ensuring it returns true when passed the parent/context node, and another fix that improves error callstack accuracy. These updates were made possible with contributions from community members, and they set the stage for more enhancements in 2022.