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Astro server islands: CORS for deferred HTML fragments, hybrid rendering, and client-side fetch after hydration
Islands may request JSON from a separate API—ensure CORS headers on the API match the page’s public origin.
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astroserver-islandscors
View transitions
SPA-style navigation after View Transitions can re-trigger cross-origin fetches—retest CORS on each route.
Persistent elements may keep stale `fetch` caches—bust cache after auth changes.
Adapters
Node adapter versus serverless differ in header size limits—large Allow-Headers lists can fail silently.
Image optimization endpoints need CORS if loaded from another subdomain in multi-zone setups.