Updating props passed via boolean operation break reactivity

[tipy02]

Describe the bug

Upgrading from svelte 5.20.0 to 5.46.3 I find some of my code lost reactivity due to prop update.

As described in doc https://svelte.dev/docs/svelte/$props#Updating-props

doing that is possible and the provided demo works well.

But in my code I pass a boolean operation to the child component instead of a boolean as in the example and it proven that it make a difference.

Reproduction

https://svelte.dev/playground/f5bec8a0be534b048f819df28bb3453c?version=5.46.3

Logs

System Info

System:
    OS: Linux 6.8 Ubuntu 24.04.3 LTS 24.04.3 LTS (Noble Numbat)
    CPU: (8) x64 Intel(R) Core(TM) i7-8665U CPU @ 1.90GHz
    Memory: 4.56 GB / 15.43 GB
    Container: Yes
    Shell: 5.2.21 - /bin/bash
  Binaries:
    Node: 24.12.0 - /home/loic/.nvm/versions/node/v24.12.0/bin/node
    npm: 11.6.2 - /home/loic/.nvm/versions/node/v24.12.0/bin/npm
  npmPackages:
    svelte: ^5.46.3 => 5.46.3 
    webpack: ^5.104.1 => 5.104.1

Severity

annoyance

[tipy02]

One workaround of that I found for my case: https://svelte.dev/playground/f7576a506b1a4c27965fd7af64803b53?version=5.46.3

[ptrxyz]

I dont think there is a problem or maybe i don't get it.
Once your counter is > 0, the bools do not change and thus would not update the props inside the children.

For clarity I added the booleans next to the buttons: https://svelte.dev/playground/01a06aef4b95463d923ac33b170a8690?version=5.46.3

You will see that first, the bools will be 'true' 'false' 'true' and after the first click and they are 'false' 'true' 'false'. No any following click to the parent button won't change the bools. They will always stay at false, true, false and thus there won't be an update pushed to the child component.

The last child component receives the actual count and for that reason will also get updated for any click on the parent button.

[tipy02]

My bad the provided reproduction was not targeting the real behavior as I tried to change the version to 5.20.0 and the behavior was the same.

I edited the playground link to some example that more like my code and in which using 5.20.0 really make a difference.