Reactivity issue on initial render when using remote functions

[techniq]

Describe the bug

We have been exploring using remote function for the new LayerChart docs but have been encountering some reactivity and performance issues (and I could 💯 be holding them wrong or have a bug in LayerChart).

If you refresh a page which triggers the <svelte:boundary> pending snippet ("loading..."), reactivity on the page is broken with no errors in the console. Performing a few interactions appears to restore reactivity:

• Toggle to Canvas (as well as back to Svg)
• Toggle to Multi and back to Single
• Navigate to a different page and back (refreshing reintroduces the issue)

CleanShot.2025-10-17.at.08.37.44.mp4

This seems to only effect pages/examples which use remote functions to load data. For example, Arc works fine

CleanShot.2025-10-17.at.08.48.24.mp4

Note: we are also having very significant performance issues (clicking on AreaChart, LineChart, etc will typically lock up your browser for a bit), but I will open a separate issue for this.

Reproduction

Check out LayerChart PR 659 and run pnpm dev (or run pnpm package in packages/layerchart and pnpm dev in `docs)

GeoCircle is a good isolated example of the reactivity issue, but it also affects Tooltips

Logs

Nothing in browser console

System Info

System:
    OS: macOS 15.5
    CPU: (10) arm64 Apple M1 Max
    Memory: 75.89 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.17.0 - /Users/techniq/Library/Caches/fnm_multishells/33654_1760650476647/bin/node
    npm: 10.9.2 - /Users/techniq/Library/Caches/fnm_multishells/33654_1760650476647/bin/npm
    pnpm: 10.18.2 - /Users/techniq/Library/pnpm/pnpm
    bun: 1.1.33 - /Users/techniq/.bun/bin/bun
  Browsers:
    Brave Browser: 136.1.78.102
    Chrome: 141.0.7390.108
    Firefox: 143.0.1
    Safari: 18.5

Severity

blocking an upgrade

[techniq]

Fixed with svelte@5.41.2. Performance issue still remains with latest svelte/kit