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perf: skip reactive overhead during SSR and avoid V8 hidden class mutations #91562

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perf: skip reactive overhead during SSR and avoid V8 hidden class mutations #91562

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9bcb7aa
perf: skip unnecessary reactive setup during SSR
benfavre Mar 18, 2026
34ed23a
fix: remove overlapping changes handled by PR #91560
benfavre Mar 18, 2026
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11 changes: 4 additions & 7 deletions packages/next/src/server/base-server.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1541,14 +1541,11 @@ export default abstract class Server<
}
parsedUrl.pathname = normalizeResult.pathname

for (const key of Object.keys(parsedUrl.query)) {
delete parsedUrl.query[key]
}
// Replace the query object instead of loop-deleting every key.
// Using `delete` on object properties mutates V8 hidden classes,
// which de-optimises inline caches on downstream property accesses.
const invokeQuery = getRequestMeta(req, 'invokeQuery')

if (invokeQuery) {
Object.assign(parsedUrl.query, invokeQuery)
}
parsedUrl.query = invokeQuery ? { ...invokeQuery } : {}

finished = await this.normalizeAndAttachMetadata(req, res, parsedUrl)
if (finished) return
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7 changes: 5 additions & 2 deletions packages/next/src/shared/lib/loadable.shared-runtime.tsx
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Expand Up @@ -196,7 +196,10 @@ class LoadableSubscription {
if (typeof opts.delay === 'number') {
if (opts.delay === 0) {
this._state.pastDelay = true
} else {
} else if (typeof window !== 'undefined') {
// Skip timers during SSR — the render is synchronous,
// there are no subscribers to notify, and the timers
// would leak in the Node.js process.
this._delay = setTimeout(() => {
this._update({
pastDelay: true,
Expand All @@ -205,7 +208,7 @@ class LoadableSubscription {
}
}

if (typeof opts.timeout === 'number') {
if (typeof opts.timeout === 'number' && typeof window !== 'undefined') {
this._timeout = setTimeout(() => {
this._update({ timedOut: true })
}, opts.timeout)
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