diff --git a/packages/next/src/server/base-server.ts b/packages/next/src/server/base-server.ts
index 66aecaf5fcba99..8a1fda1892ca86 100644
--- a/packages/next/src/server/base-server.ts
+++ b/packages/next/src/server/base-server.ts
@@ -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
diff --git a/packages/next/src/shared/lib/loadable.shared-runtime.tsx b/packages/next/src/shared/lib/loadable.shared-runtime.tsx
index d82563ed97fcf6..c6152e1713c774 100644
--- a/packages/next/src/shared/lib/loadable.shared-runtime.tsx
+++ b/packages/next/src/shared/lib/loadable.shared-runtime.tsx
@@ -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,
@@ -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)