Babashka runtime has been updated to version 0.0.30 which includes babashka 0.4.1. If you would like to upgrade then you have to: 1. remove the stack on cloudformation UI 2. remove the bucket with runtime 3. bump version in bb.edn runtimeversion 4. run bb stack:sync to deploy new version I'm aware that it's quite complicated procedure therefore I'm working to improve it a little. From the next version stack names of babashka layer will change their name therefore old layers will not be visible (you will have to remove the old layers by hand). New babashka runtime stack name allows me to better query the cloudformation output. bb stack:doctor will output available layers deployed so that you can simply switch the runtime using the ARN provided. bb stack:sync will automatically check if version declared in bb.edn is newer then currently deployed. If so new version will be deployed 🙂