how do I use the project version inside a task so that the task gets updated once the project version changes?

Add it as an input of your task.

task.yourInput.set(provider { project.version })

so simply accessing project.version inside a task is a bad idea, correct?

yes, not because the version, but the project instance

thanks!

Anything cannot be easily injected with

@Inject

probably should be passed as an input but avoiding global things like project and so on

Gradle allows you injecting easily a ObjectFactory or a ProviderFactory. But they do not allow you injecting Project, that is a guide about what to avoid.

ok, gotcha

A good way to see possible issues is, create a test kit test with configuration cache enabled

I guess I could also just auto configure tasks with

inputs.property("version", project.version)

You could set the convention of your property in the constructor of the task. But usually you shouldn't. It is best practice that tasks and extensions are as opinionless as possible to maximize reusability, and that plugins that register tasks than add opinion by setting the conventions on the properties and wiring extension properties to task properties and so on.