Turbopack: reduce hmr chunk list subscriptions by wbinnssmith · Pull Request #94062 · vercel/next.js

wbinnssmith · 2026-05-23T00:03:35Z

Previously, we created chunk list register chunks for every reachable chunk in the chunk graph on a page. Now, we only create one that subscribes to all recursively reachable assets.

This has to pass around an explicit list of client references chunks as those cannot be discovered via the chunk graph alone.

This results in a significant performance improvement when loading pages with the dev server, improving performance of a 60s cold build in a large app by about 10s.

vercel

Additional Suggestion:

Missing extra_chunks parameter in evaluated_chunk_group_assets call causes compilation error in snapshot tests.

github-actions · 2026-05-23T01:09:16Z

Tests Passed

Commit: a483b67

github-actions · 2026-05-26T17:02:09Z

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Commit: a483b67
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This adds the chunk's file path to the span as metadata.

…references Each chunk_group call for RSC client references previously generated a Dynamic EcmascriptDevChunkList, creating one subscription per client component group. Remove the Dynamic chunk list from chunk_group and pass client reference chunks as extra_chunks to evaluated_chunk_group, merging them into the single Entry chunk list the browser already subscribes to.

wbinnssmith commented May 23, 2026

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Comment thread packages/next-routing/tsconfig.json

wbinnssmith requested review from lukesandberg and sokra May 23, 2026 00:08

wbinnssmith marked this pull request as ready for review May 23, 2026 00:08

vercel Bot reviewed May 23, 2026

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sokra reviewed May 26, 2026

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Comment thread turbopack/crates/turbopack-browser/src/chunking_context.rs Outdated

sokra reviewed May 26, 2026

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Comment thread crates/next-core/src/next_app/app_client_references_chunks.rs Outdated

sokra reviewed May 26, 2026

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Comment thread crates/next-core/src/next_app/app_client_shared_chunks.rs Outdated

wbinnssmith force-pushed the wbinnssmith/hmr-flatten-chunklist branch from 9560751 to c79c2d6 Compare May 26, 2026 17:01

wbinnssmith force-pushed the wbinnssmith/hmr-flatten-chunklist branch from c79c2d6 to 21af9e8 Compare May 26, 2026 18:31

wbinnssmith force-pushed the wbinnssmith/add-chunk-name-get-hmr-subscription branch from 99aeb0d to 6b4c7e5 Compare May 26, 2026 18:31

wbinnssmith force-pushed the wbinnssmith/hmr-flatten-chunklist branch from 21af9e8 to 2d4b4f3 Compare May 26, 2026 20:04

wbinnssmith force-pushed the wbinnssmith/add-chunk-name-get-hmr-subscription branch from 6b4c7e5 to 7cad598 Compare May 26, 2026 20:07

wbinnssmith force-pushed the wbinnssmith/hmr-flatten-chunklist branch 2 times, most recently from 63afe13 to cdc75f1 Compare May 26, 2026 20:22

wbinnssmith marked this pull request as draft May 26, 2026 22:36

wbinnssmith force-pushed the wbinnssmith/add-chunk-name-get-hmr-subscription branch from 7cad598 to 554bdfa Compare May 27, 2026 19:04

lukesandberg reviewed May 27, 2026

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wbinnssmith force-pushed the wbinnssmith/hmr-flatten-chunklist branch from 409cf9c to 0caa23a Compare May 27, 2026 21:05

wbinnssmith force-pushed the wbinnssmith/add-chunk-name-get-hmr-subscription branch 2 times, most recently from d6241a6 to 019b601 Compare May 27, 2026 21:32

wbinnssmith force-pushed the wbinnssmith/hmr-flatten-chunklist branch 3 times, most recently from 6b4d5ac to c4b26d1 Compare May 28, 2026 00:39

wbinnssmith force-pushed the wbinnssmith/add-chunk-name-get-hmr-subscription branch from 019b601 to b9c71c2 Compare May 28, 2026 02:29

wbinnssmith force-pushed the wbinnssmith/hmr-flatten-chunklist branch from 6b4d5ac to b46ae83 Compare May 28, 2026 02:29