Significant performance impact 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 performance issues (and I could 💯 be holding them wrong or have a bug in LayerChart).

For example, AreaChart has 5 examples which fetch large data from /static/*via prerender().

Loading the AreaChart page from navigation can take over 1 min

CleanShot.2025-10-17.at.09.52.47.mp4

but oddly if you refresh the page it only takes about 8 seconds

CleanShot.2025-10-17.at.09.58.33.mp4

I created an AreaChartSimple page which comments out these 5 examples, and navigation takes about 5 seconds

CleanShot.2025-10-17.at.10.12.55.mp4

The current docs takes about 4 seconds to a load all the examples (using +page.ts load())

CleanShot.2025-10-17.at.10.02.06.mp4

Note: There are some known performance regressions since ~5.36.0, but this is much more significant.

Reproduction

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

Navigating to AreaChart or any other route using remote functions (search $derived(await) will present the slow performance on navigation. See AreaChartSimple or other routes which do not use remote functions for comparison.

You can also run the current docs by running pnpm dev:svelte in packages/layerchart

Logs

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