Add experimental flag for View Transitions

[eps1lon]

Will be stacked on next React sync which includes unstable_ViewTransition.

Allows using React's unstable_ViewTransition Component behind the experimental.viewTransition flag.

Right now it just opts into React's experimental build but may later house Next.js specific features like Transition Types for navigations.

[eps1lon]

• Add experimental flag for View Transitions #74659 👈 (View in Graphite)
• Upgrade React from 42687267-20250108 to 74ea0c73-20250109 #74693
• canary

This stack of pull requests is managed by Graphite. Learn more about stacking.

[ijjk]

Failing test suites

Commit: e317289

pnpm test-start test/e2e/app-dir/segment-cache/incremental-opt-in/segment-cache-incremental-opt-in.test.ts

• segment cache (incremental opt in) > prefetches a shared layout on a PPR-enabled route that was previously omitted from a non-PPR-enabled route

Expand output

● segment cache (incremental opt in) › prefetches a shared layout on a PPR-enabled route that was previously omitted from a non-PPR-enabled route

thrown: "Exceeded timeout of 120000 ms for a test.
Add a timeout value to this test to increase the timeout, if this is a long-running test. See https://jestjs.io/docs/api#testname-fn-timeout."

  94 |   })
  95 |
> 96 |   it(
     |   ^
  97 |     'prefetches a shared layout on a PPR-enabled route that was previously ' +
  98 |       'omitted from a non-PPR-enabled route',
  99 |     async () => {

  at it (e2e/app-dir/segment-cache/incremental-opt-in/segment-cache-incremental-opt-in.test.ts:96:3)
  at Object.describe (e2e/app-dir/segment-cache/incremental-opt-in/segment-cache-incremental-opt-in.test.ts:5:1)

Read more about building and testing Next.js in contributing.md.

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	vercel/next.js sebbie/01-08-add_experimental_flag_for_view_transitions	Change
buildDuration	25.7s	22.8s	N/A
buildDurationCached	21.6s	19s	N/A
nodeModulesSize	418 MB	418 MB	⚠️ +2.51 kB
nextStartRea..uration (ms)	577ms	588ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	vercel/next.js sebbie/01-08-add_experimental_flag_for_view_transitions	Change
5306-HASH.js gzip	53.3 kB	53.3 kB	N/A
8276.HASH.js gzip	169 B	168 B	N/A
8377-HASH.js gzip	5.44 kB	5.44 kB	N/A
bccd1874-HASH.js gzip	53 kB	53 kB	✓
framework-HASH.js gzip	57.5 kB	57.5 kB	N/A
main-app-HASH.js gzip	240 B	242 B	N/A
main-HASH.js gzip	34.1 kB	34.1 kB	N/A
webpack-HASH.js gzip	1.71 kB	1.71 kB	N/A
Overall change	53 kB	53 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js sebbie/01-08-add_experimental_flag_for_view_transitions	Change
polyfills-HASH.js gzip	39.4 kB	39.4 kB	✓
Overall change	39.4 kB	39.4 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js sebbie/01-08-add_experimental_flag_for_view_transitions	Change
_app-HASH.js gzip	193 B	193 B	✓
_error-HASH.js gzip	193 B	193 B	✓
amp-HASH.js gzip	512 B	510 B	N/A
css-HASH.js gzip	343 B	342 B	N/A
dynamic-HASH.js gzip	1.84 kB	1.84 kB	✓
edge-ssr-HASH.js gzip	265 B	265 B	✓
head-HASH.js gzip	363 B	362 B	N/A
hooks-HASH.js gzip	393 B	392 B	N/A
image-HASH.js gzip	4.57 kB	4.57 kB	N/A
index-HASH.js gzip	268 B	268 B	✓
link-HASH.js gzip	2.35 kB	2.34 kB	N/A
routerDirect..HASH.js gzip	328 B	328 B	✓
script-HASH.js gzip	397 B	397 B	✓
withRouter-HASH.js gzip	323 B	326 B	N/A
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	3.59 kB	3.59 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js sebbie/01-08-add_experimental_flag_for_view_transitions	Change
_buildManifest.js gzip	749 B	747 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js sebbie/01-08-add_experimental_flag_for_view_transitions	Change
index.html gzip	523 B	523 B	✓
link.html gzip	538 B	537 B	N/A
withRouter.html gzip	519 B	520 B	N/A
Overall change	523 B	523 B	✓

Edge SSR bundle Size

	vercel/next.js canary	vercel/next.js sebbie/01-08-add_experimental_flag_for_view_transitions	Change
edge-ssr.js gzip	128 kB	128 kB	N/A
page.js gzip	207 kB	207 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	vercel/next.js sebbie/01-08-add_experimental_flag_for_view_transitions	Change
middleware-b..fest.js gzip	670 B	669 B	N/A
middleware-r..fest.js gzip	155 B	156 B	N/A
middleware.js gzip	31.2 kB	31.2 kB	N/A
edge-runtime..pack.js gzip	844 B	844 B	✓
Overall change	844 B	844 B	✓

Next Runtimes

	vercel/next.js canary	vercel/next.js sebbie/01-08-add_experimental_flag_for_view_transitions	Change
274-experime...dev.js gzip	322 B	322 B	✓
274.runtime.dev.js gzip	314 B	314 B	✓
app-page-exp...dev.js gzip	368 kB	368 kB	✓
app-page-exp..prod.js gzip	129 kB	129 kB	✓
app-page-tur..prod.js gzip	142 kB	142 kB	✓
app-page-tur..prod.js gzip	138 kB	138 kB	✓
app-page.run...dev.js gzip	355 kB	355 kB	✓
app-page.run..prod.js gzip	126 kB	126 kB	✓
app-route-ex...dev.js gzip	37.6 kB	37.6 kB	✓
app-route-ex..prod.js gzip	25.6 kB	25.6 kB	✓
app-route-tu..prod.js gzip	25.6 kB	25.6 kB	✓
app-route-tu..prod.js gzip	25.4 kB	25.4 kB	✓
app-route.ru...dev.js gzip	39.2 kB	39.2 kB	✓
app-route.ru..prod.js gzip	25.4 kB	25.4 kB	✓
pages-api-tu..prod.js gzip	9.69 kB	9.69 kB	✓
pages-api.ru...dev.js gzip	11.6 kB	11.6 kB	✓
pages-api.ru..prod.js gzip	9.68 kB	9.68 kB	✓
pages-turbo...prod.js gzip	21.7 kB	21.7 kB	✓
pages.runtim...dev.js gzip	27.5 kB	27.5 kB	✓
pages.runtim..prod.js gzip	21.7 kB	21.7 kB	✓
server.runti..prod.js gzip	916 kB	916 kB	✓
Overall change	2.46 MB	2.46 MB	✓

build cache Overall increase ⚠️

	vercel/next.js canary	vercel/next.js sebbie/01-08-add_experimental_flag_for_view_transitions	Change
0.pack gzip	2.09 MB	2.09 MB	⚠️ +2.19 kB
index.pack gzip	73.8 kB	75 kB	⚠️ +1.19 kB
Overall change	2.17 MB	2.17 MB	⚠️ +3.38 kB

Diff details

Diff for page.js

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Diff for edge-ssr.js

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Diff for main-HASH.js

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Commit: e317289