Downlevel static blocks in build step by mischnic · Pull Request #97863 · vercel/next.js

mischnic · 2026-08-25T10:11:56Z

Apps built with Webpack fail because of this:

          // Support Safari 15 on a best-effort basis: it cannot parse static
          // class initialization blocks (added in Safari 16.4), so always
          // downlevel them (`static #_ = this.x = ...`) even though the
          // browserslist targets support them.

Turbopack isn't affected because it always transpiles all modules, whether it's node_modules or not.

Co-authored-by: Niklas Mischkulnig <4586894+mischnic@users.noreply.github.com>

github-actions · 2026-08-25T10:12:15Z

Failing test suites

Commit: 703b71b | About building and testing Next.js

pnpm test-dev-turbo test/development/acceptance-app/app-hmr-changes.test.ts (turbopack) (job)

Error overlay - RSC build errors > Skipped in webpack > should handle successive HMR changes with errors correctly (DD)

Expand output

● Error overlay - RSC build errors › Skipped in webpack › should handle successive HMR changes with errors correctly

Application is in inconsistent state: timeout.

  114 |             }
  115 |             if (status !== 'pending') {
> 116 |               throw new Error(
      |                     ^
  117 |                 `Application is in inconsistent state: ${status}.`
  118 |               )
  119 |             }

  at Object.patch (lib/development-sandbox.ts:116:21)
  at Object.<anonymous> (development/acceptance-app/app-hmr-changes.test.ts:58:11)

github-actions · 2026-08-25T10:12:16Z

Stats from current PR

🟢 1 improvement

Metric	Canary	PR	Change	Trend
Webpack Build Time (cached)	25.099s	24.531s	🟢 568ms (-2%)	▁▁▂█▂

📊 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)	812ms	812ms	✓	█████
Cold (Ready in log)	794ms	794ms	✓	▂▃▅▅▆
Cold (First Request)	1.263s	1.261s	✓	▁▃▅▆▇
Warm (Listen)	813ms	811ms	✓	█████
Warm (Ready in log)	783ms	789ms	✓	▂▄▆▅▆
Warm (First Request)	1.239s	1.244s	✓	▁▃▇▅▇

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	814ms	813ms	✓	▁▁▂█▁
Cold (Ready in log)	806ms	805ms	✓	▁▁▂█▂
Cold (First Request)	3.462s	3.453s	✓	▁▁▂█▂
Warm (Listen)	813ms	814ms	✓	▁▁▁█▁
Warm (Ready in log)	809ms	808ms	✓	▁▁▁█▁
Warm (First Request)	3.500s	3.513s	✓	▁▁▂█▁

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	5.621s	5.596s	✓	▁▁▇▇▆
Cached Build	2.869s	2.910s	✓	▁▁▅▇▇

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	24.762s	24.688s	✓	▁▁▁█▂
Cached Build	25.099s	24.531s	🟢 568ms (-2%)	▁▁▂█▂
node_modules Size	553 MB	553 MB	✓	█████

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles

	Canary	PR	Change
017_4moyv5m34.js gzip	117 B	117 B	✓
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1m5vdnlf0deiv.js gzip	411 B	411 B	✓
1nigpy_mr0xvj.js gzip	339 B	N/A	-
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3kvxagoobts7h.js gzip	117 B	N/A	-
3p99hd9vwe6ae.js gzip	13 kB	N/A	-
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3wijk2ywqgsv9.js gzip	2.52 kB	N/A	-
41kebu3wv5f4d.js gzip	65.5 kB	N/A	-
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05x5p94ucjhna.js gzip	N/A	2.29 kB	-
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0longconn5mlm.js gzip	N/A	123 B	-
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Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	1.02 kB	1.02 kB	✓
Total	1.02 kB	1.02 kB	⚠️ +1 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	846 B	845 B	✓
Total	846 B	845 B	✅ -1 B

Build Cache

	Canary	PR	Change
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00000014.sst gzip	59 B	59 B	✓
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00000020.sst gzip	59 B	59 B	✓
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CURRENT gzip	94 B	93 B	🟢 1 B (-1%)
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Total	79.6 MB	79.6 MB	✅ -40 kB

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
3322-HASH.js gzip	65.7 kB	N/A	-
4191.HASH.js gzip	169 B	N/A	-
9784-HASH.js gzip	5.57 kB	N/A	-
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framework-HASH.js gzip	59.7 kB	59.7 kB	✓
main-app-HASH.js gzip	253 B	252 B	✓
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webpack-HASH.js gzip	1.68 kB	1.68 kB	✓
3577.HASH.js gzip	N/A	168 B	-
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Total	236 kB	236 kB	⚠️ +116 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	181 B	182 B	✓
css-HASH.js gzip	334 B	331 B	✓
dynamic-HASH.js gzip	1.81 kB	1.81 kB	✓
edge-ssr-HASH.js gzip	255 B	253 B	✓
head-HASH.js gzip	349 B	351 B	✓
hooks-HASH.js gzip	382 B	384 B	✓
image-HASH.js gzip	5.02 kB	5.01 kB	✓
index-HASH.js gzip	260 B	259 B	✓
link-HASH.js gzip	2.48 kB	2.48 kB	✓
routerDirect..HASH.js gzip	317 B	318 B	✓
script-HASH.js gzip	384 B	386 B	✓
withRouter-HASH.js gzip	316 B	315 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Total	12.4 kB	12.4 kB	✅ -3 B

Server

Edge SSR

	Canary	PR	Change
edge-ssr.js gzip	128 kB	128 kB	✓
page.js gzip	293 kB	293 kB	✓
Total	421 kB	421 kB	✅ -525 B

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	600 B	601 B	✓
middleware-r..fest.js gzip	156 B	156 B	✓
middleware.js gzip	45.7 kB	45.3 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	47.3 kB	46.9 kB	✅ -428 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	698 B	698 B	✓
Total	698 B	698 B	✓

Build Cache

	Canary	PR	Change
0.pack gzip	4.8 MB	4.79 MB	🟢 5.49 kB (0%)
index.pack gzip	123 kB	123 kB	✓
index.pack.old gzip	122 kB	123 kB	✓
Total	5.04 MB	5.04 MB	✅ -4.61 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	375 kB	375 kB	✓
app-page-exp..prod.js gzip	206 kB	206 kB	✓
app-page-tur...dev.js gzip	374 kB	374 kB	✓
app-page-tur..prod.js gzip	206 kB	206 kB	✓
app-page-tur...dev.js gzip	370 kB	370 kB	✓
app-page-tur..prod.js gzip	204 kB	204 kB	✓
app-page.run...dev.js gzip	371 kB	371 kB	✓
app-page.run..prod.js gzip	204 kB	204 kB	✓
app-route-ex...dev.js gzip	82.5 kB	82.5 kB	✓
app-route-ex..prod.js gzip	55.6 kB	55.6 kB	✓
app-route-tu...dev.js gzip	82.5 kB	82.5 kB	✓
app-route-tu..prod.js gzip	55.6 kB	55.6 kB	✓
app-route-tu...dev.js gzip	82.1 kB	82.1 kB	✓
app-route-tu..prod.js gzip	55.4 kB	55.4 kB	✓
app-route.ru...dev.js gzip	82.1 kB	82.1 kB	✓
app-route.ru..prod.js gzip	55.4 kB	55.4 kB	✓
dev-validati...dev.js gzip	134 kB	134 kB	✓
dev-validati...dev.js gzip	134 kB	134 kB	✓
dev-validati...dev.js gzip	132 kB	132 kB	✓
dev-validati...dev.js gzip	132 kB	132 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	46.2 kB	46.2 kB	✓
pages-api-tu..prod.js gzip	34.3 kB	34.3 kB	✓
pages-api.ru...dev.js gzip	46.2 kB	46.2 kB	✓
pages-api.ru..prod.js gzip	34.3 kB	34.3 kB	✓
pages-turbo....dev.js gzip	54.6 kB	54.6 kB	✓
pages-turbo...prod.js gzip	39.7 kB	39.7 kB	✓
pages.runtim...dev.js gzip	54.6 kB	54.6 kB	✓
pages.runtim..prod.js gzip	39.6 kB	39.6 kB	✓
server.runti..prod.js gzip	65.9 kB	65.9 kB	✓
use-cache-pr...dev.js gzip	73.3 kB	73.3 kB	✓
use-cache-pr...dev.js gzip	73.3 kB	73.3 kB	✓
use-cache-pr...dev.js gzip	71.5 kB	71.5 kB	✓
use-cache-pr...dev.js gzip	71.5 kB	71.5 kB	✓
Total	4.1 MB	4.1 MB	⚠️ +27 B

📝 Changed Files (8 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

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app-page-exp..time.prod.js

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app-page-tur..ntime.dev.js

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app-page-tur..time.prod.js

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app-page-tur..ntime.dev.js

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app-page-tur..time.prod.js

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app-page.runtime.dev.js

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app-page.runtime.prod.js

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📎 Tarball URL

https://vercel-packages.vercel.app/next/commits/703b71b4b1f40d7d222af85c644c7668a362f3f4/next

Commit: 703b71b

vercel-fleet-prod Bot and others added 2 commits August 25, 2026 09:14

build: downlevel static class initializer blocks in client output

f0c1883

Co-authored-by: Niklas Mischkulnig <4586894+mischnic@users.noreply.github.com>

docs: explain static block downleveling as best-effort Safari 15 support

703b71b

Co-authored-by: Niklas Mischkulnig <4586894+mischnic@users.noreply.github.com>

lukesandberg approved these changes Aug 25, 2026

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Downlevel static blocks in build step - #97863

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