Experimental deferred entries handling #88347

ijjk · 2026-01-09T20:33:55Z

This is just an exploration into a deferred entries hook in next.config

nextjs-bot · 2026-01-09T20:40:20Z

Failing test suites

Commit: 5dff961 | About building and testing Next.js

pnpm test-start test/e2e/deferred-entries/deferred-entries.test.ts (job)

deferred-entries webpack > should call onBeforeDeferredEntries before processing deferred entries during build (DD)

Expand output

● deferred-entries webpack › should call onBeforeDeferredEntries before processing deferred entries during build

expect(received).toBeLessThanOrEqual(expected)

Expected: <= 1767994032177
Received:    1767994033179

  187 |         ...deferredPageEntries.map((e) => e.timestamp)
  188 |       )
> 189 |       expect(callbackTimestamp).toBeLessThanOrEqual(earliestDeferredTimestamp)
      |                                 ^
  190 |
  191 |       // Verify the home page works
  192 |       const homeRes = await next.fetch('/')

  at Object.toBeLessThanOrEqual (e2e/deferred-entries/deferred-entries.test.ts:189:33)

vercel · 2026-01-09T20:46:02Z

packages/next/src/server/dev/on-demand-entry-handler.ts

+          ([, entry]) => {
+            const entryData = entry as Entry | ChildEntry
+            if (entryData.type !== EntryTypes.ENTRY) return false
+
+            const isDeferred = isDeferredEntry(
+              (entryData as Entry).absolutePagePath
+                .replace(appDir || '', '')
+                .replace(pagesDir || '', '')
+                .replace(rootDir, ''),


String replacement approach to extract page path from absolutePagePath is fragile and produces incorrect results when passed to isDeferredEntry

This bug is confirmed by the failing test. The test shows that deferred entries are being processed before the callback is called, which indicates that the fragile path extraction is incorrectly identifying which entries are deferred. The fix extracts the page path directly from the entryKey instead of trying to parse it from the file system path, which should resolve both this test failure and the underlying logic bug.

vercel · 2026-01-09T20:46:02Z

packages/next/src/build/webpack/plugins/deferred-entries-plugin.ts

+  private onBeforeDeferredEntries?: () => Promise<void>
+  private deferredEntrypoints?: webpack.EntryObject
+  private callbackCalled: boolean = false
+


DeferredEntriesPlugin's callbackCalled flag persists across HMR compilation cycles, preventing the onBeforeDeferredEntries callback from being called on subsequent hot reloads

This bug prevents the onBeforeDeferredEntries callback from being called on subsequent HMR cycles in development mode. The fix resets the callbackCalled flag when a new compilation starts by hooking into compiler.hooks.invalid, ensuring consistent behavior across all HMR cycles.

nextjs-bot · 2026-01-09T20:56:01Z

Stats from current PR

🔴 1 regression

Metric	Canary	PR	Change	Trend
node_modules Size	457 MB	458 MB	🔴 +1.08 MB (+0%)	█████

📊 All Metrics

📖 Metrics Glossary

Dev Server Metrics:

Listen = TCP port starts accepting connections
First Request = HTTP server returns successful response
Cold = Fresh build (no cache)
Warm = With cached build artifacts

Build Metrics:

Fresh = Clean build (no .next directory)
Cached = With existing .next directory

Change Thresholds:

Time: Changes < 50ms AND < 10%, OR < 2% are insignificant
Size: Changes < 1KB AND < 1% are insignificant
All other changes are flagged to catch regressions

⚡ Dev Server

Metric	Canary	PR	Change	Trend
Cold (Listen)	456ms	456ms	✓	▁▁▁▁▁
Cold (First Request)	814ms	819ms	✓	█▇▁▇█
Warm (Listen)	456ms	456ms	✓	▁▁▁▁▁
Warm (First Request)	338ms	336ms	✓	▇█▇▄▇

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	506ms	506ms	✓	█▁▁▁▁
Cold (First Request)	1.803s	1.781s	✓	▁▄▅▄▅
Warm (Listen)	457ms	506ms	✓	▅█▁▅▅
Warm (First Request)	1.833s	1.829s	✓	▁▅▄▄▅

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	4.191s	4.194s	✓	▂▁▂▁▁
Cached Build	4.209s	4.169s	✓	▁▁▂▁▁

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	14.692s	14.668s	✓	▁▂▁▁▃
Cached Build	14.752s	14.756s	✓	▂▂▁▁▃
node_modules Size	457 MB	458 MB	🔴 +1.08 MB (+0%)	█████

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles: **430 kB** → **431 kB** ⚠️ +448 B

82 files with content-based hashes (individual files not comparable between builds)

Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	793 B	787 B	✓
Total	793 B	787 B	✅ -6 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	449 B	450 B	✓
Total	449 B	450 B	⚠️ +1 B

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
2086.HASH.js gzip	169 B	N/A	-
2161-HASH.js gzip	5.41 kB	N/A	-
2747-HASH.js gzip	4.48 kB	N/A	-
4322-HASH.js gzip	52.7 kB	N/A	-
ec793fe8-HASH.js gzip	62.3 kB	N/A	-
framework-HASH.js gzip	59.8 kB	59.8 kB	✓
main-app-HASH.js gzip	252 B	254 B	✓
main-HASH.js gzip	38.6 kB	38.9 kB	✓
webpack-HASH.js gzip	1.68 kB	1.68 kB	✓
1596.HASH.js gzip	N/A	169 B	-
2658-HASH.js gzip	N/A	52.5 kB	-
6349-HASH.js gzip	N/A	4.46 kB	-
7019-HASH.js gzip	N/A	5.42 kB	-
b17a3386-HASH.js gzip	N/A	62.3 kB	-
Total	225 kB	225 kB	⚠️ +136 B

Polyfills

	Canary	PR	Change
polyfills-HASH.js gzip	39.4 kB	39.4 kB	✓
Total	39.4 kB	39.4 kB	✓

Pages

	Canary	PR	Change
_app-HASH.js gzip	194 B	193 B	✓
_error-HASH.js gzip	182 B	182 B	✓
css-HASH.js gzip	336 B	335 B	✓
dynamic-HASH.js gzip	1.8 kB	1.8 kB	✓
edge-ssr-HASH.js gzip	256 B	256 B	✓
head-HASH.js gzip	352 B	349 B	✓
hooks-HASH.js gzip	385 B	384 B	✓
image-HASH.js gzip	580 B	580 B	✓
index-HASH.js gzip	259 B	258 B	✓
link-HASH.js gzip	2.5 kB	2.51 kB	✓
routerDirect..HASH.js gzip	319 B	317 B	✓
script-HASH.js gzip	385 B	387 B	✓
withRouter-HASH.js gzip	316 B	315 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Total	7.97 kB	7.96 kB	✅ -8 B

Server

Edge SSR

	Canary	PR	Change
edge-ssr.js gzip	125 kB	125 kB	✓
page.js gzip	239 kB	241 kB	🔴 +2.48 kB (+1%)
Total	364 kB	366 kB	⚠️ +2.51 kB

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	653 B	652 B	✓
middleware-r..fest.js gzip	155 B	156 B	✓
middleware.js gzip	32.7 kB	33.2 kB	🔴 +521 B (+2%)
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	34.3 kB	34.9 kB	⚠️ +521 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	738 B	738 B	✓
Total	738 B	738 B	✓

Build Cache

	Canary	PR	Change
0.pack gzip	3.6 MB	3.64 MB	🔴 +36.1 kB (+1%)
index.pack gzip	98.4 kB	99.7 kB	🔴 +1.33 kB (+1%)
index.pack.old gzip	98.2 kB	99.6 kB	🔴 +1.42 kB (+1%)
Total	3.8 MB	3.84 MB	⚠️ +38.9 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	303 kB	303 kB	✓
app-page-exp..prod.js gzip	157 kB	158 kB	✓
app-page-tur...dev.js gzip	302 kB	303 kB	✓
app-page-tur..prod.js gzip	157 kB	158 kB	✓
app-page-tur...dev.js gzip	299 kB	300 kB	✓
app-page-tur..prod.js gzip	155 kB	156 kB	✓
app-page.run...dev.js gzip	299 kB	300 kB	✓
app-page.run..prod.js gzip	155 kB	156 kB	✓
app-route-ex...dev.js gzip	68.2 kB	68.7 kB	✓
app-route-ex..prod.js gzip	46.9 kB	47.5 kB	🔴 +629 B (+1%)
app-route-tu...dev.js gzip	68.2 kB	68.8 kB	✓
app-route-tu..prod.js gzip	46.9 kB	47.6 kB	🔴 +630 B (+1%)
app-route-tu...dev.js gzip	67.8 kB	68.4 kB	✓
app-route-tu..prod.js gzip	46.7 kB	47.3 kB	🔴 +632 B (+1%)
app-route.ru...dev.js gzip	67.8 kB	68.3 kB	✓
app-route.ru..prod.js gzip	46.7 kB	47.3 kB	🔴 +631 B (+1%)
dist_client_...dev.js gzip	324 B	324 B	✓
dist_client_...dev.js gzip	326 B	326 B	✓
dist_client_...dev.js gzip	318 B	318 B	✓
dist_client_...dev.js gzip	317 B	317 B	✓
pages-api-tu...dev.js gzip	41.1 kB	41.1 kB	✓
pages-api-tu..prod.js gzip	31.2 kB	31.2 kB	✓
pages-api.ru...dev.js gzip	41.1 kB	41.1 kB	✓
pages-api.ru..prod.js gzip	31.2 kB	31.2 kB	✓
pages-turbo....dev.js gzip	50.8 kB	50.8 kB	✓
pages-turbo...prod.js gzip	38.2 kB	38.2 kB	✓
pages.runtim...dev.js gzip	50.8 kB	50.8 kB	✓
pages.runtim..prod.js gzip	38.2 kB	38.2 kB	✓
server.runti..prod.js gzip	62 kB	62.2 kB	✓
Total	2.67 MB	2.68 MB	⚠️ +11 kB

📝 Changed Files (21 files)

Files with changes:

app-page-exp..ntime.dev.js
app-page-exp..time.prod.js
app-page-tur..ntime.dev.js
app-page-tur..time.prod.js
app-page-tur..ntime.dev.js
app-page-tur..time.prod.js
app-page.runtime.dev.js
app-page.runtime.prod.js
app-route-ex..ntime.dev.js
app-route-ex..time.prod.js
app-route-tu..ntime.dev.js
app-route-tu..time.prod.js
app-route-tu..ntime.dev.js
app-route-tu..time.prod.js
app-route.runtime.dev.js
app-route.ru..time.prod.js
pages-turbo...ntime.dev.js
pages-turbo...time.prod.js
pages.runtime.dev.js
pages.runtime.prod.js
... and 1 more

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codspeed-hq · 2026-01-09T21:43:20Z

Merging this PR will not alter performance

✅ 17 untouched benchmarks
⏩ 3 skipped benchmarks¹

_{Comparing ijjk/deferred-entries (5dff961) with canary (77c69a7)}

3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

Save deferred entries dev support

18938d6

nextjs-bot added created-by: Next.js team PRs by the Next.js team. tests Turbopack Related to Turbopack with Next.js. type: next labels Jan 9, 2026

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5dff961

ijjk force-pushed the ijjk/deferred-entries branch from e958a74 to 5dff961 Compare January 9, 2026 21:21

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Experimental deferred entries handling #88347

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