0604 — the transition's ready promise is caught at the source
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Context
Supersedes [0603], same day. That record made the tier-3 net skip
every unhandled DOMException named AbortError or InvalidStateError —
over-broad, since InvalidStateError is a wrong-state programming-error
class the net could now hide. Research located the actual leak and the
ecosystem’s answer: Chrome skips same-document view transitions on
mobile (a live Chromium regression, issue 456078987, also behind the
devtools mobile emulator) and rejects the transition’s ready promise
with InvalidStateError while the navigation completes; the spec marks
ready handled on skip but Chrome leaks it, and a CSSWG thread
(css-view-transitions-2 #13726) is weighing spec fixes. Astro’s router
attaches no handler to ready (unfixed upstream, issue #10830 closed
unreproduced); Nuxt fixed the identical leak in its own router with an
empty catch on finished (PR #34515) and ready (PR #35537). Nobody
filters exception names at a global net.
Decision
- listenForPageFailures registers one more listener: on
astro:before-swap,event.viewTransition.ready.catch(() => {})— the Nuxt fix applied at Astro’s event seam, since the router itself is not ours to patch. The type import fromastro:transitions/clientis type-only, so Storybook’s svelte-vite build never sees the virtual module. - The unhandledrejection net goes back to fully strict: the [0603] name filter is removed. A real InvalidStateError anywhere else reaches the banner again.
- In Astro’s no-view-transition fallback,
readyaliases the update promise the router already awaits in its own try/catch — the extra catch changes nothing there.
Consequences
- If a leak ever surfaces through a promise this seam cannot reach (Astro derives an unhandled chain internally), the banner returns and says so — preferred over a silent global filter.
- Worth filing upstream on Astro: their router should catch
readyas Nuxt’s does; this listener becomes deletable when it does, or when Chrome ships the spec’s mark-as-handled on this path.