bits-ui no longer works after updating to Svelte 5.31.0

[dcheglakov]

Describe the bug

After upgrading Svelte from version 5.30.2 to 5.31.0 or newer, the bits-ui library stopped working completely. Everything functioned as expected with svelte@5.30.2, but once we updated to svelte@5.31.0, the components from bits-ui no longer render or behave properly.

Steps to Reproduce:

1. Checkout reproduction repo.
2. Set svelte version to 5.30.2 — everything works fine.
3. Upgrade to svelte@5.31.0 or later — bits-ui components break.

Reproduction

https://github.com/dcheglakov/bits-ui-svelte

Logs

TypeError: Cannot read properties of undefined (reading 'disabled')
    at /Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/accordion.svelte.js:97:47
    at <instance_members_initializer> (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/accordion.svelte.js:99:41)
    at new AccordionTriggerState (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/accordion.svelte.js:100:16)
    at useAccordionTrigger (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/accordion.svelte.js:319:9)
    at Module.Accordion_trigger (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/components/accordion-trigger.svelte:16:42)
    at eval (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/src/routes/+page.svelte:18:40)
    at Module.Accordion_header (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/components/accordion-header.svelte:32:20)
    at eval (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/src/routes/+page.svelte:16:38)
    at Module.Accordion_item (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/components/accordion-item.svelte:34:20)
    at eval (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/src/routes/+page.svelte:14:36)
TypeError: Cannot read properties of undefined (reading 'disabled')
    at /Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/accordion.svelte.js:97:47
    at <instance_members_initializer> (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/accordion.svelte.js:99:41)
    at new AccordionTriggerState (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/accordion.svelte.js:100:16)
    at useAccordionTrigger (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/accordion.svelte.js:319:9)
    at Module.Accordion_trigger (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/components/accordion-trigger.svelte:16:42)
    at eval (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/src/routes/+page.svelte:18:40)
    at Module.Accordion_header (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/components/accordion-header.svelte:32:20)
    at eval (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/src/routes/+page.svelte:16:38)
    at Module.Accordion_item (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/node_modules/.pnpm/bits-ui@1.5.3_svelte@5.33.0/node_modules/bits-ui/dist/bits/accordion/components/accordion-item.svelte:34:20)
    at eval (/Users/dcheglakov/Development/dcheglakov/bits-ui-svelte/src/routes/+page.svelte:14:36)

System Info

System:
    OS: macOS 15.5
    CPU: (12) arm64 Apple M3 Pro
    Memory: 99.89 MB / 36.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.14.0 - ~/.nvm/versions/node/v22.14.0/bin/node
    npm: 10.9.2 - ~/.nvm/versions/node/v22.14.0/bin/npm
    pnpm: 10.10.0 - ~/.nvm/versions/node/v22.14.0/bin/pnpm
  Browsers:
    Safari: 18.5
  npmPackages:
    @sveltejs/kit: ^2.21.1 => 2.21.1 
    bits-ui: ^1.5.3 => 1.5.3 
    svelte: ^5.33.0 => 5.33.0

Severity

blocking all usage of bits-ui

[symsmith]

This issue is already tracked in #1465, it is an issue with Svelte itself. Please use Svelte 5.30.2 until sveltejs/svelte#15964 is merged

[dcheglakov]

This issue is already tracked in #1465, it is an issue with Svelte itself. Please use Svelte 5.30.2 until sveltejs/svelte#15964 is merged

Thanks, I guess I can close this issue now.