[turbopack] Make shrinking logic declarative and optimize for immutable tasks #89222

lukesandberg · 2026-01-29T07:41:48Z

Use field annotations to drive what fields get 'shrunk' when a task completes.

Doing this also optimizes the implementation since instead of scanning for each field we care about we walk all fields and handle the correct subset as we find them.

Also take advantage of some features of immutable tasks (which account for about 25% of all tasks), and more aggressively drop some fields

Saves quite a bit of memory and maybe a little bit of time

lukesandberg · 2026-01-29T07:42:08Z

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nextjs-bot · 2026-01-29T07:49:33Z

Tests Passed

codspeed-hq · 2026-01-29T08:02:07Z

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing better_shrinking (63cc9ce) with canary (47c3507)}

Summary

✅ 17 untouched benchmarks
⏩ 3 skipped benchmarks¹

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. ↩

nextjs-bot · 2026-01-29T08:03:56Z

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)	456ms	456ms	✓	▁▁▁█▁
Cold (Ready in log)	449ms	449ms	✓	███▆▆
Cold (First Request)	874ms	876ms	✓	▇▇▆▇▇
Warm (Listen)	457ms	455ms	✓	█▁█▁▁
Warm (Ready in log)	446ms	448ms	✓	▃▂▁▃▁
Warm (First Request)	352ms	357ms	✓	▇▅▁▅▁

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	455ms	455ms	✓	▁▁▁▁▁
Cold (Ready in log)	436ms	435ms	✓	▁▁▁▁▁
Cold (First Request)	1.813s	1.819s	✓	▁▁▁▁▁
Warm (Listen)	456ms	455ms	✓	▁▁▁▁▁
Warm (Ready in log)	435ms	435ms	✓	▁▁▁▁▁
Warm (First Request)	1.829s	1.830s	✓	▁▁▁▁▁

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	4.282s	4.395s	✓	▂▂▁▁▁
Cached Build	4.395s	4.339s	✓	▂▁▁▁▁

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	13.603s	13.624s	✓	▁▂▁▁▁
Cached Build	13.693s	13.699s	✓	▁▁▁▁▁
node_modules Size	463 MB	463 MB	✓	▁▁▁▁▁

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles: **432 kB** → **432 kB** ⚠️ +2 B

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

Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	759 B	766 B	✓
Total	759 B	766 B	⚠️ +7 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	451 B	449 B	✓
Total	451 B	449 B	✅ -2 B

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
5528-HASH.js gzip	5.47 kB	N/A	-
6280-HASH.js gzip	54.4 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	255 B	253 B	✓
main-HASH.js gzip	39 kB	39 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	55.1 kB	-
Total	228 kB	228 kB	⚠️ +690 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	247 kB	248 kB	✓
Total	374 kB	374 kB	⚠️ +315 B

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	616 B	614 B	✓
middleware-r..fest.js gzip	156 B	155 B	✓
middleware.js gzip	33.1 kB	33.1 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	34.7 kB	34.8 kB	⚠️ +55 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	3.77 MB	3.77 MB	🔴 +8 kB (+0%)
index.pack gzip	102 kB	102 kB	✓
index.pack.old gzip	103 kB	101 kB	🟢 1.16 kB (-1%)
Total	3.97 MB	3.98 MB	⚠️ +7.07 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	308 kB	308 kB	✓
app-page-exp..prod.js gzip	164 kB	164 kB	✓
app-page-tur...dev.js gzip	308 kB	308 kB	✓
app-page-tur..prod.js gzip	164 kB	164 kB	✓
app-page-tur...dev.js gzip	305 kB	305 kB	✓
app-page-tur..prod.js gzip	162 kB	162 kB	✓
app-page.run...dev.js gzip	305 kB	305 kB	✓
app-page.run..prod.js gzip	162 kB	162 kB	✓
app-route-ex...dev.js gzip	70.2 kB	70.2 kB	✓
app-route-ex..prod.js gzip	48.8 kB	48.8 kB	✓
app-route-tu...dev.js gzip	70.2 kB	70.2 kB	✓
app-route-tu..prod.js gzip	48.8 kB	48.8 kB	✓
app-route-tu...dev.js gzip	69.8 kB	69.8 kB	✓
app-route-tu..prod.js gzip	48.6 kB	48.6 kB	✓
app-route.ru...dev.js gzip	69.8 kB	69.8 kB	✓
app-route.ru..prod.js gzip	48.6 kB	48.6 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	43.1 kB	43.1 kB	✓
pages-api-tu..prod.js gzip	32.8 kB	32.8 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	39.3 kB	39.3 kB	✓
pages.runtim...dev.js gzip	52.3 kB	52.3 kB	✓
pages.runtim..prod.js gzip	39.3 kB	39.3 kB	✓
server.runti..prod.js gzip	62.5 kB	62.5 kB	✓
Total	2.75 MB	2.75 MB	⚠️ +1 B

lukesandberg · 2026-01-30T00:14:58Z

Merge activity

Jan 30, 12:14 AM UTC: @lukesandberg merged this pull request with Graphite.

nextjs-bot added created-by: Turbopack team PRs by the Turbopack team. Turbopack Related to Turbopack with Next.js. labels Jan 29, 2026

lukesandberg mentioned this pull request Jan 29, 2026

[turbopack] mark persistent_task_type as inline #89185

Merged

lukesandberg changed the title ~~better shrinking logic~~ [turbopack] Make shrinking logic declarative and optimize for immutable tasks Jan 29, 2026

lukesandberg force-pushed the task_memory_tracking branch from 448c393 to aa9ffab Compare January 29, 2026 16:45

lukesandberg force-pushed the better_shrinking branch from c7ef6df to 8f787c6 Compare January 29, 2026 16:45

lukesandberg mentioned this pull request Jan 29, 2026

Improve consistency of how Flag typed fields are handled in the macro to more structurally prevent bugs like what was fixed in #89228 #89255

Open

lukesandberg marked this pull request as ready for review January 29, 2026 18:05

lukesandberg requested a review from a team January 29, 2026 18:05

lukesandberg changed the base branch from task_memory_tracking to graphite-base/89222 January 29, 2026 18:22

better shrinking logic

63cc9ce

lukesandberg force-pushed the better_shrinking branch from 8f787c6 to 63cc9ce Compare January 29, 2026 19:18

lukesandberg force-pushed the graphite-base/89222 branch from aa9ffab to 47c3507 Compare January 29, 2026 19:18

lukesandberg changed the base branch from graphite-base/89222 to canary January 29, 2026 19:18

bgw approved these changes Jan 29, 2026

View reviewed changes

lukesandberg merged commit 1608789 into canary Jan 30, 2026
391 of 421 checks passed

lukesandberg deleted the better_shrinking branch January 30, 2026 00:14

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[turbopack] Make shrinking logic declarative and optimize for immutable tasks #89222

[turbopack] Make shrinking logic declarative and optimize for immutable tasks #89222

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[turbopack] Make shrinking logic declarative and optimize for immutable tasks #89222

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