As part of GoCD 14.1, we officially announced Task plugins. Because tasks inherently are executed on an agent, we had to make few changes in the agent-bootstrapper component to allow this. Unlike the agent component which upgrades automatically to remain compatible with the server version, the agent-bootstrapper has to be manually upgraded.
Although we keep the agent-bootstrapper lean and flexible, which rarely requires changes to it, this was one situation where we had to make a change in it. As a result, GoCD Administrators will need to upgrade their agent installations (by using the go-agent installers appropriate to their go-server installation) before they can use the task-plugins in GoCD.
Note: Although agent-bootstrapper versions >= 12.3 is capable of handling this feature, we recommend upgrading your go-server and go-agents to the latest release.