Upgrade React from `bef88f7c-20260116` to `41b3e9a6-20260119` #88756

eps1lon · 2026-01-19T17:03:11Z

diff facebook/react@bef88f7c...41b3e9a6

React upstream changes

Closes https://linear.app/vercel/issue/NAR-532/

nextjs-bot · 2026-01-19T17:12:08Z

Tests Passed

nextjs-bot · 2026-01-19T17:21:23Z

Stats from current PR

🔴 1 regression

Metric	Canary	PR	Change	Trend
node_modules Size	458 MB	458 MB	🔴 +173 kB (+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)	455ms	455ms	✓	▁▁▁▁▁
Cold (Ready in log)	437ms	437ms	✓	▇██▆▁
Cold (First Request)	1.172s	1.187s	✓	████▁
Warm (Listen)	456ms	456ms	✓	▁▁▁▁▁
Warm (Ready in log)	442ms	442ms	✓	▁▁▁▁▃
Warm (First Request)	342ms	337ms	✓	▇▆▃▇▆

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	455ms	455ms	✓	▁▁▁▁▁
Cold (Ready in log)	439ms	439ms	✓	▇▅█▇▁
Cold (First Request)	1.815s	1.846s	✓	▅▃▇▄▁
Warm (Listen)	456ms	456ms	✓	▁▁▁▁▁
Warm (Ready in log)	439ms	440ms	✓	▅▄▅▅▁
Warm (First Request)	1.833s	1.843s	✓	▄▃▅▃▁

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	4.355s	4.321s	✓	▁▁▁▁▃
Cached Build	4.288s	4.354s	✓	▁▁▁▁▃

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	14.064s	14.070s	✓	▁▁▆▁▁
Cached Build	14.153s	14.197s	✓	▁▁▆▁▁
node_modules Size	458 MB	458 MB	🔴 +173 kB (+0%)	█████

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles: **430 kB** → **430 kB** ✅ -93 B

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

Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	762 B	764 B	✓
Total	762 B	764 B	⚠️ +2 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	450 B	449 B	✓
Total	450 B	449 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	52.3 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	251 B	254 B	🔴 +3 B (+1%)
main-HASH.js gzip	38.6 kB	39 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	51.9 kB	-
6349-HASH.js gzip	N/A	4.46 kB	-
7019-HASH.js gzip	N/A	5.43 kB	-
b17a3386-HASH.js gzip	N/A	62.3 kB	-
Total	225 kB	225 kB	✅ -3 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	243 kB	238 kB	🟢 4.9 kB (-2%)
Total	368 kB	363 kB	✅ -4.89 kB

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	618 B	618 B	✓
middleware-r..fest.js gzip	155 B	156 B	✓
middleware.js gzip	32.9 kB	33.3 kB	🔴 +377 B (+1%)
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	34.5 kB	34.9 kB	⚠️ +378 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	3.66 MB	3.67 MB	🔴 +4.54 kB (+0%)
index.pack gzip	100 kB	101 kB	✓
index.pack.old gzip	99.8 kB	99.6 kB	✓
Total	3.86 MB	3.87 MB	⚠️ +4.53 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	304 kB	304 kB	✓
app-page-exp..prod.js gzip	158 kB	158 kB	✓
app-page-tur...dev.js gzip	304 kB	304 kB	✓
app-page-tur..prod.js gzip	158 kB	158 kB	✓
app-page-tur...dev.js gzip	300 kB	301 kB	✓
app-page-tur..prod.js gzip	156 kB	156 kB	✓
app-page.run...dev.js gzip	300 kB	301 kB	✓
app-page.run..prod.js gzip	156 kB	156 kB	✓
app-route-ex...dev.js gzip	68.8 kB	68.8 kB	✓
app-route-ex..prod.js gzip	47.6 kB	47.6 kB	✓
app-route-tu...dev.js gzip	68.8 kB	68.8 kB	✓
app-route-tu..prod.js gzip	47.6 kB	47.6 kB	✓
app-route-tu...dev.js gzip	68.4 kB	68.4 kB	✓
app-route-tu..prod.js gzip	47.4 kB	47.4 kB	✓
app-route.ru...dev.js gzip	68.4 kB	68.4 kB	✓
app-route.ru..prod.js gzip	47.4 kB	47.4 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	41.2 kB	41.2 kB	✓
pages-api-tu..prod.js gzip	31.3 kB	31.3 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	50.7 kB	50.7 kB	✓
pages.runtim..prod.js gzip	38.2 kB	38.2 kB	✓
server.runti..prod.js gzip	62.2 kB	62.2 kB	✓
Total	2.69 MB	2.69 MB	⚠️ +2.59 kB

📝 Changed Files (10 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..time.prod.js
app-route-tu..time.prod.js

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

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app-page.runtime.dev.js

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app-page.runtime.prod.js

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app-route-ex..time.prod.js

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app-route-tu..time.prod.js

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unstubbable

Looked at the last two commits, looks good to me!

nextjs-bot added created-by: Next.js team PRs by the Next.js team. type: next labels Jan 19, 2026

eps1lon added the type: react-sync label Jan 19, 2026

eps1lon self-assigned this Jan 19, 2026

nextjs-bot added the tests label Jan 19, 2026

nextjs-bot and others added 8 commits January 19, 2026 20:48

Update react@experimental

485e072

Update react

3f650ee

Updated peer dependency references in apps

e1a926e

Updated peer dependency references in libraries

45f3364

Update lockfile

f13ed0c

ncc-compiled

a0a5e3a

Update now passing tests

07a8c23

Add test for stalled use()

ea89635

eps1lon force-pushed the update/react/19.3.0-canary-41b3e9a6-20260119 branch from eabd0e5 to ea89635 Compare January 19, 2026 19:49

eps1lon marked this pull request as ready for review January 19, 2026 20:06

eps1lon requested a review from unstubbable January 19, 2026 20:06

eps1lon enabled auto-merge (squash) January 19, 2026 20:08

unstubbable approved these changes Jan 19, 2026

View reviewed changes

eps1lon merged commit a77fd58 into canary Jan 19, 2026
289 of 291 checks passed

eps1lon deleted the update/react/19.3.0-canary-41b3e9a6-20260119 branch January 19, 2026 20:44

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Upgrade React from `bef88f7c-20260116` to `41b3e9a6-20260119` #88756

Upgrade React from `bef88f7c-20260116` to `41b3e9a6-20260119` #88756

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📦 Production Builds (Webpack)

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Upgrade React from bef88f7c-20260116 to 41b3e9a6-20260119 #88756

Upgrade React from bef88f7c-20260116 to 41b3e9a6-20260119 #88756

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Stats from current PR

🔴 1 regression

⚡ Dev Server

📦 Dev Server (Webpack)

⚡ Production Builds

📦 Production Builds (Webpack)

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Upgrade React from `bef88f7c-20260116` to `41b3e9a6-20260119` #88756

Upgrade React from `bef88f7c-20260116` to `41b3e9a6-20260119` #88756

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