Version

3.1.1

Reproduction link

https://codesandbox.io/s/quirky-microservice-snj0b?file=/src/App.vue

Steps to reproduce

click the button

What is expected?

watch cannot triggered

What is actually happening?

watch is triggered

you should:

<Comp :config="config" />

setup(){
const config = {a:1}
return{
    ...
    config
    }
}

By passing the object directly as a prop, every render creates a new object, effectively triggering the watcher.

Please, next time consider using the forum, the Discord server or StackOverflow for questions first. But feel free to come back and open an issue if it turns out to be a bug 🙂