Svelte 5.19.5 breaks reactivity, Svelte 5.19.4 works fine

[patoi]

Describe the bug

In Svelte 5.19.4 reactivity works fine, but in 5.19.5 it's failing.

https://svelte.dev/playground/9a92552dd0204d93b4e76e4247103358?version=5.19.4

vs

https://svelte.dev/playground/9a92552dd0204d93b4e76e4247103358?version=5.19.5

Reproduction

https://svelte.dev/playground/9a92552dd0204d93b4e76e4247103358?version=5.19.5

Use case: Typing login name and password enables Login button.

In Svelte 5.19.5 it doesn't work: When I enter the login name and password, the Login button remains disabled. After I select the login name input field and type it again, the Login button becomes enabled.

Expected: When I enter the login name and password, the Login button becomes enabled. It works fine in Svelte 5.19.4

Logs

System Info

Svelte Playground

Severity

blocking all usage of svelte

[dummdidumm]

FYI @trueadm this is likely due to a regression in #15137

[trueadm]

Looking into it now

[gyzerok]

Interesting! Noticed that if you first touch password and then login, it works fine

[andriuwe4ka]

Just wrap in boolean and it works:

disabled={Boolean(!loginname ||! password)}