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<https://docs.gradle.org/8.5/userguide/configuration_cache.html#config_cache:requirements:task_extensions>
&gt; <https://docs.gradle.org/8.5/userguide/configuration_cache.html#config_cache:requirements:task_extensions|Accessing task extensions or conventions>
&gt; 
&gt; Tasks should not access conventions and extensions, including extra properties, at execution time. Instead, any value that’s relevant for the execution of the task should be modeled as a task property.

I guess so, otherwise I would also have said it should work

So mainly an educated guess without the answer to your question., but my educated guesses are usually quite accurate :smile:

The specific case I'm dealing with is actually `testTask.extensions.findByType(JacocoTaskExtension.class)`

I'm not sure how to model that as a property, since I don't control the definition of that type

This is a Gradle extension on a Gradle type; does Gradle itself give me a way to do this?

It depends where you are using `testTask.extensions` . Looks like you're using from a task action. If you control that task, and an input property there. If not, report the issue to whoever is accessing this

I tried to solve this for <@U03JYHHAC5B> unsuccessfully only because the JacocoTaskExtension is not a proper Lazy Configuration enabled class. It holds onto an internalized `Property&lt;File&gt;` as a destinationFile but does not allow consumers full access to the property as is more commonly done. Instead it provides these three accessors/mutators.

```
    @Nullable
    @Optional
    @OutputFile
    public File getDestinationFile() {
        return (File)this.destinationFile.getOrNull();
    }

    public void setDestinationFile(Provider&lt;File&gt; destinationFile) {
        this.destinationFile.set(destinationFile);
    }

    public void setDestinationFile(File destinationFile) {
        this.destinationFile.set(destinationFile);
    }```
If I need to observe the value of destinationFile but not mutate it I cannot do so in a lazy configuration way.

To make matters worse I cannot set the JacocoTaskExtension as input property to another task, it is not serializable friendly.

&gt; because the JacocoTaskExtension is not a proper Lazy Configuration enabled class
Hopefully with Gradle 9 this changes.
&gt; If I need to observe the value of destinationFile but not mutate it I cannot do so in a lazy configuration way.
How about `testTask.map { it.jacoco.destinationFile!! }`?

Hmm, I always forget the `map()` option. That is a very interesting alternative. I already started on an alternate path but I will give that a shot. Thanks <@URQ797WRW>