simplify session dependent tasks (#91729) by lukesandberg · Pull Request #92358 · vercel/next.js

lukesandberg · 2026-04-04T19:11:30Z

Summary

This is a re-application of #91729 without the TTL support (fetch Cache-Control and TransientState changes are excluded).

Make `session_dependent` a function attribute

Previously, tasks called mark_session_dependent() at runtime to flag themselves. This PR makes it a compile-time #[turbo_tasks::function(session_dependent)] attribute instead. Benefits:

Enables eager aggregation number selection: Session-dependent tasks change on every session restore, behaving like dirty leaf nodes. By knowing at task creation time (not mid-execution) that a task is session-dependent, the backend can assign a high initial aggregation number, preventing long dirty-propagation chains through intermediate aggregated nodes.
Simpler API: No runtime mark_session_dependent() call needed — the attribute is declarative and statically checked.
Removes mark_session_dependent(), mark_own_task_as_session_dependent(), and the session_dependent field from InProgressStateInner. The backend now reads is_session_dependent directly from the NativeFunction metadata via TaskGuard::is_session_dependent().

Test Plan

Existing tests continue to pass
cargo check -p turbo-tasks -p turbo-tasks-backend -p turbo-tasks-fetch

Closes NEXT-

lukesandberg · 2026-04-04T19:11:51Z

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codspeed-hq · 2026-04-04T19:31:41Z

Merging this PR will not alter performance

✅ 8 untouched benchmarks
⏩ 12 skipped benchmarks¹

_{Comparing re_apply_session_dependent_tasks (c7c7689) with canary (21c28c8)}

12 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 · 2026-04-04T19:40:33Z

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)	457ms	455ms	✓	▅▅▅▁█
Cold (Ready in log)	443ms	444ms	✓	▇█▂▁▂
Cold (First Request)	1.129s	1.124s	✓	▆██▆▁
Warm (Listen)	455ms	457ms	✓	▁▁██▁
Warm (Ready in log)	442ms	449ms	✓	▇█▁▂▂
Warm (First Request)	346ms	342ms	✓	▅▇▁▃▅

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	456ms	456ms	✓	▆▃▆▃▃
Cold (Ready in log)	438ms	438ms	✓	▆▃▂▁▃
Cold (First Request)	1.947s	1.950s	✓	█▄▆▇▇
Warm (Listen)	456ms	456ms	✓	▁▁▁▁▁
Warm (Ready in log)	439ms	438ms	✓	▆▃▃▁▂
Warm (First Request)	1.957s	1.974s	✓	▇▃▆▆▇

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	3.875s	3.973s	✓	▅█▅▇▆
Cached Build	3.962s	3.925s	✓	▄▅█▅█

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	14.480s	14.613s	✓	▇▁▁▁▂
Cached Build	14.627s	14.682s	✓	█▃▂▁▂
node_modules Size	488 MB	488 MB	✓	▅████

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nextjs-bot added created-by: Turbopack team PRs by the Turbopack team. Turbopack Related to Turbopack with Next.js. labels Apr 4, 2026

This was referenced Apr 4, 2026

tiny debugging hacks #92357

Draft

fetch: respect HTTP Cache-Control headers with TTL-based invalidation (#91729) #92322

Draft

lukesandberg changed the base branch from streaming_reads_and_caches to graphite-base/92358 April 6, 2026 17:26

lukesandberg force-pushed the graphite-base/92358 branch from ec9f7f3 to 2be529b Compare April 6, 2026 17:26

lukesandberg force-pushed the re_apply_session_dependent_tasks branch from f5f9dc0 to 0cae08f Compare April 6, 2026 17:26

lukesandberg changed the base branch from graphite-base/92358 to 04-06-streaming_reads April 6, 2026 17:27

This was referenced Apr 6, 2026

change the process name of builds #92411

Merged

[turbopack] Tracing and debugging fixes #92412

Closed

[turbopack] Reduce persistence buffer lifetimes #92413

Closed

lukesandberg force-pushed the re_apply_session_dependent_tasks branch from 0cae08f to 70da271 Compare April 6, 2026 17:46

lukesandberg force-pushed the 04-06-streaming_reads branch from 2be529b to 2bc6c08 Compare April 6, 2026 17:46

lukesandberg force-pushed the re_apply_session_dependent_tasks branch from 70da271 to 781db31 Compare April 6, 2026 17:57

lukesandberg force-pushed the 04-06-streaming_reads branch from 2bc6c08 to 76294c3 Compare April 6, 2026 17:57

This was referenced Apr 6, 2026

Fix sst inspect tool to respect CURRENT and stale sst files #92414

Merged

[turbopack] add family name to many spans #92415

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lukesandberg force-pushed the 04-06-streaming_reads branch from 76294c3 to 632c22b Compare April 6, 2026 20:11

lukesandberg force-pushed the re_apply_session_dependent_tasks branch 2 times, most recently from 0522d66 to 00769ef Compare April 6, 2026 20:26

lukesandberg force-pushed the 04-06-streaming_reads branch from c275d99 to 806bd09 Compare April 7, 2026 16:23

lukesandberg force-pushed the re_apply_session_dependent_tasks branch from 00769ef to a550e51 Compare April 7, 2026 16:24

simplify session dependent tasks (#91729)

c7c7689

lukesandberg changed the base branch from 04-06-streaming_reads to graphite-base/92358 April 8, 2026 00:04

lukesandberg force-pushed the re_apply_session_dependent_tasks branch from a550e51 to c7c7689 Compare April 8, 2026 00:04

lukesandberg force-pushed the graphite-base/92358 branch from 806bd09 to 21c28c8 Compare April 8, 2026 00:04

lukesandberg changed the base branch from graphite-base/92358 to canary April 8, 2026 00:04

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simplify session dependent tasks (#91729)#92358

simplify session dependent tasks (#91729)#92358
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Make session_dependent a function attribute

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Merging this PR will not alter performance

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lukesandberg commented Apr 4, 2026 •

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Make `session_dependent` a function attribute

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