Handle Pages data route skew with deployment id header, take 2 by mischnic · Pull Request #89325 · vercel/next.js

mischnic · 2026-01-30T23:07:06Z

Deployment skew (forcing a MPA nav instead of a SPA nav if a deployment happened inbetween) is handled by comparing a header on the client side.
- The other case that used build ids was app router, which was changed to the same approach in Replace flight navigation build id field with header #88855
Then, when a deployment id is available, make the build id a constant
- Particularly, this makes the rollout of this much easier as the data route paths stay the same (both in Next.js itself as well as in the builder)

If you use output:export and set config.deploymentId (i.e. enable skew protection) you are still expected to set these headers.

mischnic · 2026-01-30T23:07:35Z

Proper e2e test of function determinism - adapter #89522
Proper e2e test of function determinism #88908
Handle Pages data route skew with deployment id header, take 2 #89325 👈 (View in Graphite)
Replace flight navigation build id field with header #88855 : 1 other dependent PR (#89112 )
canary

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packages/next/src/server/normalizers/request/next-data.test.ts

nextjs-bot · 2026-01-30T23:29:17Z

Stats from current PR

✅ No significant changes detected

📊 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)	455ms	454ms	✓	▁▁▁▁▁
Cold (Ready in log)	438ms	437ms	✓	▂▂▂▁▁
Cold (First Request)	1.147s	1.198s	✓	▅▅▄▁▁
Warm (Listen)	456ms	457ms	✓	▁▁▁▁▁
Warm (Ready in log)	443ms	446ms	✓	▁▁▁▁▁
Warm (First Request)	339ms	343ms	✓	▁▂▂▁▂

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	456ms	455ms	✓	▁▁▁▁█
Cold (Ready in log)	449ms	450ms	✓	▄▆▅▆█
Cold (First Request)	1.931s	1.922s	✓	▃▆▄▆█
Warm (Listen)	456ms	456ms	✓	▁▁▁▁█
Warm (Ready in log)	450ms	450ms	✓	▅▅▅▆█
Warm (First Request)	1.938s	1.918s	✓	▃▄▃▅█

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	3.921s	3.961s	✓	▁▁▁▃▂
Cached Build	3.968s	4.011s	✓	▁▁▁▃▂

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	14.679s	14.657s	✓	▁▃▁▄█
Cached Build	14.694s	14.665s	✓	▁▃▁▄█
node_modules Size	464 MB	465 MB	✓	▁▁▁▁▁

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles: **437 kB** → **437 kB** ⚠️ +75 B

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

Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	770 B	766 B	✓
Total	770 B	766 B	✅ -4 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	450 B	450 B	✓
Total	450 B	450 B	✓

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
5528-HASH.js gzip	5.47 kB	N/A	-
6280-HASH.js gzip	56.8 kB	N/A	-
6335.HASH.js gzip	169 B	N/A	-
912-HASH.js gzip	4.53 kB	N/A	-
e8aec2e4-HASH.js gzip	62.5 kB	N/A	-
framework-HASH.js gzip	59.7 kB	59.7 kB	✓
main-app-HASH.js gzip	256 B	254 B	✓
main-HASH.js gzip	39 kB	39.1 kB	✓
webpack-HASH.js gzip	1.68 kB	1.68 kB	✓
262-HASH.js gzip	N/A	4.52 kB	-
2889.HASH.js gzip	N/A	169 B	-
5602-HASH.js gzip	N/A	5.48 kB	-
6948ada0-HASH.js gzip	N/A	62.5 kB	-
9544-HASH.js gzip	N/A	57.4 kB	-
Total	230 kB	231 kB	⚠️ +661 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	194 B	✓
_error-HASH.js gzip	183 B	180 B	🟢 3 B (-2%)
css-HASH.js gzip	331 B	330 B	✓
dynamic-HASH.js gzip	1.81 kB	1.81 kB	✓
edge-ssr-HASH.js gzip	256 B	256 B	✓
head-HASH.js gzip	351 B	352 B	✓
hooks-HASH.js gzip	384 B	383 B	✓
image-HASH.js gzip	580 B	581 B	✓
index-HASH.js gzip	260 B	260 B	✓
link-HASH.js gzip	2.49 kB	2.49 kB	✓
routerDirect..HASH.js gzip	320 B	319 B	✓
script-HASH.js gzip	386 B	386 B	✓
withRouter-HASH.js gzip	315 B	315 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Total	7.97 kB	7.97 kB	✅ -1 B

Server

Edge SSR

	Canary	PR	Change
edge-ssr.js gzip	126 kB	126 kB	✓
page.js gzip	249 kB	249 kB	✓
Total	375 kB	375 kB	⚠️ +113 B

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	614 B	617 B	✓
middleware-r..fest.js gzip	156 B	155 B	✓
middleware.js gzip	33 kB	33 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	34.6 kB	34.6 kB	⚠️ +15 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	732 B	736 B	✓
Total	732 B	736 B	⚠️ +4 B

Build Cache

	Canary	PR	Change
0.pack gzip	3.81 MB	3.83 MB	🔴 +12.8 kB (+0%)
index.pack gzip	103 kB	103 kB	✓
index.pack.old gzip	103 kB	103 kB	✓
Total	4.02 MB	4.03 MB	⚠️ +13.4 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	312 kB	312 kB	✓
app-page-exp..prod.js gzip	166 kB	166 kB	✓
app-page-tur...dev.js gzip	311 kB	311 kB	✓
app-page-tur..prod.js gzip	166 kB	166 kB	✓
app-page-tur...dev.js gzip	308 kB	308 kB	✓
app-page-tur..prod.js gzip	164 kB	164 kB	✓
app-page.run...dev.js gzip	308 kB	308 kB	✓
app-page.run..prod.js gzip	164 kB	164 kB	✓
app-route-ex...dev.js gzip	70.4 kB	70.4 kB	✓
app-route-ex..prod.js gzip	48.9 kB	48.9 kB	✓
app-route-tu...dev.js gzip	70.4 kB	70.4 kB	✓
app-route-tu..prod.js gzip	49 kB	49 kB	✓
app-route-tu...dev.js gzip	70 kB	70 kB	✓
app-route-tu..prod.js gzip	48.7 kB	48.7 kB	✓
app-route.ru...dev.js gzip	70 kB	70 kB	✓
app-route.ru..prod.js gzip	48.7 kB	48.7 kB	✓
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	43.2 kB	43.2 kB	✓
pages-api-tu..prod.js gzip	32.9 kB	32.9 kB	✓
pages-api.ru...dev.js gzip	43.1 kB	43.1 kB	✓
pages-api.ru..prod.js gzip	32.8 kB	32.8 kB	✓
pages-turbo....dev.js gzip	52.4 kB	52.4 kB	✓
pages-turbo...prod.js gzip	39.4 kB	39.4 kB	✓
pages.runtim...dev.js gzip	52.4 kB	52.4 kB	✓
pages.runtim..prod.js gzip	39.3 kB	39.3 kB	✓
server.runti..prod.js gzip	62.6 kB	62.6 kB	✓
Total	2.78 MB	2.78 MB	✅ -1 B

nextjs-bot · 2026-02-03T10:55:18Z

Failing test suites

Commit: f7f0c15 | About building and testing Next.js

test/e2e/pages-ssg-data-deployment-skew/pages-ssg-data-deployment-skew.test.ts

codspeed-hq · 2026-02-03T11:12:30Z

Merging this PR will degrade performance by 6.29%

❌ 3 regressed benchmarks
✅ 14 untouched benchmarks
⏩ 3 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Simulation	`app-page-turbo.runtime.prod.js[full]`	654.1 ms	698 ms	-6.29%
❌	Simulation	`app-page-turbo.runtime.prod.js[tracing]`	571.2 ms	595.2 ms	-4.04%
❌	Simulation	`packages-bundle.js[full]`	999.1 ms	1,052.2 ms	-5.05%

_{Comparing mischnic/reapply-pages-buildid (b5483b8) with mischnic/flight-nav-requests-build-id (e0e23b6)²}

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. ↩
No successful run was found on mischnic/flight-nav-requests-build-id (b47ffc0) during the generation of this report, so a043432 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

Since vercel/next.js#89325, the build id is overridden to a hardcoded string `build-TfctsWXpff2fKS` when skew protection is enabled. https://github.com/vercel/next.js/blob/2521b8adc73957cf7dfc358bea3c461b04bcfa16/packages/next/src/build/index.ts#L906-L910 Update the e2e tests to use that instead. --------- Co-authored-by: JJ Kasper <jj@jjsweb.site>

…l#89325) Reapply vercel#88959 Revert vercel#89323 Closes PACK-6537 Closes PACK-6756 - Deployment skew (forcing a MPA nav instead of a SPA nav if a deployment happened inbetween) is handled by comparing a header on the client side. - The other case that used build ids was app router, which was changed to the same approach in vercel#88855 - Then, when a deployment id is available, make the build id a constant - Particularly, this makes the rollout of this much easier as the data route paths stay the same (both in Next.js itself as well as in the builder) If you use `output:export` and set `config.deploymentId` (i.e. enable skew protection) you are still expected to set these headers.

nextjs-bot added created-by: Turbopack team PRs by the Turbopack team. tests type: next labels Jan 30, 2026

This was referenced Jan 30, 2026

Don't include build id in runtime files if not needed #89112

Closed

Replace flight navigation build id field with header #88855

Merged

mischnic changed the title ~~Reapply "Replace build id in Pages data routes with deployment id (#88959)" (#89323)~~ Replace build id in Pages data routes with deployment id, take 2 Jan 30, 2026

vercel bot reviewed Jan 30, 2026

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packages/next/src/server/normalizers/request/next-data.test.ts Outdated Show resolved Hide resolved

mischnic changed the base branch from canary to graphite-base/89325 February 3, 2026 10:51

mischnic force-pushed the mischnic/reapply-pages-buildid branch from eaf3516 to b5483b8 Compare February 3, 2026 10:51

mischnic changed the base branch from graphite-base/89325 to mischnic/flight-nav-requests-build-id February 3, 2026 10:51

vercel bot reviewed Feb 3, 2026

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test/e2e/pages-ssg-data-deployment-skew/pages-ssg-data-deployment-skew.test.ts Outdated Show resolved Hide resolved

mischnic force-pushed the mischnic/reapply-pages-buildid branch from b5483b8 to 842c8b0 Compare February 3, 2026 13:22

mischnic changed the base branch from mischnic/flight-nav-requests-build-id to graphite-base/89325 February 3, 2026 13:23

mischnic marked this pull request as ready for review February 3, 2026 13:25

mischnic added 3 commits February 3, 2026 14:29

Improve pages router deployment skew tests

651828c

More minimal approach

bea4c8c

constant build id with skew protection

f7f0c15

mischnic force-pushed the graphite-base/89325 branch from b47ffc0 to 0aac540 Compare February 3, 2026 13:29

mischnic force-pushed the mischnic/reapply-pages-buildid branch from 842c8b0 to f7f0c15 Compare February 3, 2026 13:29

mischnic changed the base branch from graphite-base/89325 to canary February 3, 2026 13:29

mischnic requested a review from timneutkens February 3, 2026 15:04

mischnic mentioned this pull request Feb 3, 2026

Proper e2e test of function determinism #88908

Merged

timneutkens approved these changes Feb 4, 2026

View reviewed changes

mischnic changed the title ~~Replace build id in Pages data routes with deployment id, take 2~~ Replace build id in Pages data routes with deployment id header, take 2 Feb 4, 2026

mischnic changed the title ~~Replace build id in Pages data routes with deployment id header, take 2~~ Handle Pages data route skew with deployment id header, take 2 Feb 4, 2026

mischnic merged commit 49e0a8a into canary Feb 4, 2026
227 of 230 checks passed

mischnic deleted the mischnic/reapply-pages-buildid branch February 4, 2026 17:07

This was referenced Feb 5, 2026

Proper e2e test of function determinism - adapter #89522

Merged

[next] Fix e2e tests with hardcoded build id vercel/vercel#14886

Merged

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Handle Pages data route skew with deployment id header, take 2#89325

Handle Pages data route skew with deployment id header, take 2#89325
mischnic merged 3 commits intocanaryfrom
mischnic/reapply-pages-buildid

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Merging this PR will degrade performance by 6.29%

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