the bug
if i change the argument of an awaited SvelteKit remote-function query() inside a <svelte:boundary>, that renders a LayerChart chart inside - the tab hangs in what i can only assume to be a main-thread infinite js loop: cpu usage is at 100%, and the page stays frozen indefinitely. initial render (ssr and hydration) is (usually) fine; the freeze happens only when the awaited value re-resolves while the chart subtree is alive.
Filing here because LayerChart's derived graph is what the loop walks, but this might also be a svelte/sveltekit issue
repro
git clone https://github.com/teidesu/layerchart-async-repro && cd layerchart-async-repro
pnpm install
pnpm dev
if the tab didn't freeze right away - click the button once.
config: compilerOptions.experimental.async: true + kit.experimental.remoteFunctions: true.
versions
- layerchart 2.1.0
- svelte 5.56.8 (also reproduces on 5.56.4)
- @sveltejs/kit 2.63
- vite 8, Chrome 150, macOS
findings by claude fable 5
What I measured
Patched update_derived in svelte's client runtime with a counter: page load is ~13k derived updates, then a single click drives it past 2,000,000 — still climbing when I made the counter throw to free the tab. So it's an unbounded
derived re-evaluation storm, not a slow render.
Pausing the wedged renderer (debugger attached before the click) shows a ~780-frame stack cycling through:
get → update_derived → execute_derived → update_reaction → (layerchart derived) → get → ...
interleaved with nested $state-proxy ownKeys recursion through exclude_from_object (rest-props destructuring) in LayerChart's component chain (restProps = user_derived(() => exclude_from_object(props, [...])) etc. in the Chart component). The graph never settles — deriveds producing fresh object identities keep re-capturing into the async batch/fork during the boundary re-render.
Notes / controls
- Replacing the remote query with a plain local
async function of identical shape (same await in the boundary, same 100ms delay) does not reproduce. The remote-function query object is load-bearing.
- Fresh mounts are always fine; only a re-resolve over a live chart subtree freezes.
{#key data} around the chart does not help (the remount itself storms). motion: 'none' doesn't help either.
$effect.pending() is not required (this repro has none), but pages reading it freeze the same way.- Looks like a survivor of the async-mode round from last year:
sveltejs/svelte#17883 (same symptom, closed), sveltejs/svelte#16548, #626, #630 — all marked fixed, but this variant reproduces on latest svelte.
the bug
if i change the argument of an awaited SvelteKit remote-function
query()inside a<svelte:boundary>, that renders a LayerChart chart inside - the tab hangs in what i can only assume to be a main-thread infinite js loop: cpu usage is at 100%, and the page stays frozen indefinitely. initial render (ssr and hydration) is (usually) fine; the freeze happens only when the awaited value re-resolves while the chart subtree is alive.Filing here because LayerChart's derived graph is what the loop walks, but this might also be a svelte/sveltekit issue
repro
if the tab didn't freeze right away - click the button once.
config:
compilerOptions.experimental.async: true+kit.experimental.remoteFunctions: true.versions
findings by claude fable 5
What I measured
Patched
update_derivedin svelte's client runtime with a counter: page load is ~13k derived updates, then a single click drives it past 2,000,000 — still climbing when I made the counter throw to free the tab. So it's an unboundedderived re-evaluation storm, not a slow render.
Pausing the wedged renderer (debugger attached before the click) shows a ~780-frame stack cycling through:
interleaved with nested
$state-proxyownKeysrecursion throughexclude_from_object(rest-props destructuring) in LayerChart's component chain (restProps = user_derived(() => exclude_from_object(props, [...]))etc. in the Chart component). The graph never settles — deriveds producing fresh object identities keep re-capturing into the async batch/fork during the boundary re-render.Notes / controls
async functionof identical shape (sameawaitin the boundary, same 100ms delay) does not reproduce. The remote-function query object is load-bearing.{#key data}around the chart does not help (the remount itself storms).motion: 'none'doesn't help either.$effect.pending()is not required (this repro has none), but pages reading it freeze the same way.sveltejs/svelte#17883(same symptom, closed),sveltejs/svelte#16548,#626,#630— all marked fixed, but this variant reproduces on latest svelte.