perf(router-core): evaluate head/scripts across matches in parallel by Sheraff · Pull Request #8145 · TanStack/router

Sheraff · 2026-08-21T21:53:28Z

Summary

projectLane (load-server.ts + load-client.ts) awaited each match's head/scripts(/headers) sequentially — total latency was the sum of all resolutions instead of the max.
Now invokes all callbacks in the rendered prefix synchronously (route order), then awaits/applies results one match at a time in route order with the original per-match error/abort/break logic.

Behavioral equivalence (strict)

Each preserved ordering has a dedicated test in tests/head-scripts-parallel.test.ts (10 tests):

results applied in route order even when later matches resolve first
early-break semantics (ssr:false / error / _notFound) unchanged
deterministic route-order error surfacing; sync-throw handling; silent abort break
zero unhandled rejections (catch handlers attached to every promise, incl. discarded ones)

Caught during verification: a first implementation wrapped results in an extra .then layer; that single extra microtask tick flipped a real scheduling race so runBackground's publish landed after router.load() resolved — caught by the existing public-hydration-contract.test.ts. Fixed by awaiting the raw attempt promise (identical await-chain depth to original).

Performance

N=6 heads × 60ms: sequential 362ms → projectLane 62ms (~max, not sum).

Verification

test:unit ✅ (107 files / 1616 tests) · eslint ✅ · types ✅

Residual risks (documented in RESULT-perf-task4.md)

head fns for the whole prefix are invoked up-front: a fn reading another match's already-applied head result would see it unapplied (loaders are guaranteed complete first; contract tests pass).
Under abort, later prefix callbacks may be invoked before the abort is observed.

coderabbitai · 2026-08-21T22:02:20Z

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github-actions · 2026-08-21T22:04:47Z

Bundle Size Benchmarks

Commit: 6f0657277db8
Measured at: 2026-08-22T06:03:40.210Z
Baseline source: history:d83a8964c250
Dashboard: bundle-size history

The following scenarios have bundle-size changes compared with the baseline:

Scenario	Current (gzip)	Initial (gzip)	Raw	Brotli	Trend
`react-router.minimal`	83.9 KiB +52 B	83.8 KiB +56 B	263.0 KiB +177 B	73.0 KiB -3 B	▃▂▂▁▁▃▃▃▂▄▄█
`react-router.full`	87.4 KiB +58 B	87.3 KiB +57 B	274.7 KiB +177 B	76.1 KiB +93 B	▂▂▂▁▁▃▃▃▂▄▄█
`solid-router.minimal`	33.3 KiB +61 B	33.1 KiB +61 B	96.8 KiB +177 B	30.0 KiB +22 B	▁▁▁▄▄▅▅▅▅▅▅█
`solid-router.full`	38.1 KiB +61 B	38.0 KiB +60 B	111.5 KiB +177 B	34.4 KiB +108 B	▁▁▁▅▅▆▆▆▅▅▅█
`vue-router.minimal`	49.6 KiB +62 B	49.5 KiB +63 B	138.8 KiB +177 B	44.8 KiB +119 B	▁▁▁▁▁▄▄▄▂▃▃█
`vue-router.full`	55.2 KiB +62 B	55.1 KiB +62 B	157.0 KiB +177 B	49.7 KiB +42 B	▁▁▁▁▁▄▄▄▂▃▃█
`react-start.minimal`	96.8 KiB +56 B	96.7 KiB +56 B	305.2 KiB +177 B	83.9 KiB +87 B	▂▁▁▄▄▅▅▅▅▆▆█
`react-start.deferred-hydration`	97.5 KiB +61 B	96.7 KiB +57 B	306.6 KiB +177 B	84.6 KiB +76 B	▂▁▁▄▄▅▅▅▅▆▆█
`react-start.full`	100.0 KiB +53 B	99.8 KiB +53 B	315.0 KiB +177 B	86.6 KiB +79 B	▁▁▁▄▄▅▅▅▄▆▆█
`react-start.rsbuild.minimal`	100.1 KiB +64 B	99.9 KiB +64 B	315.5 KiB +177 B	86.3 KiB -89 B	▂▁▁▄▄▆▆▆▄▅▅█
`react-start.rsbuild.minimal-iife`	100.5 KiB +62 B	100.4 KiB +62 B	316.4 KiB +177 B	86.7 KiB +63 B	▂▁▁▃▃▆▆▆▄▅▅█
`react-start.rsbuild.full`	103.4 KiB +59 B	103.3 KiB +59 B	325.6 KiB +177 B	89.1 KiB +93 B	▂▁▁▃▃▆▆▆▅▅▅█
`solid-start.minimal`	46.1 KiB +55 B	46.0 KiB +55 B	137.9 KiB +177 B	41.0 KiB +78 B	▁▁▁▅▅▆▆▆▆▆▆█
`solid-start.deferred-hydration`	49.2 KiB +58 B	46.0 KiB +61 B	145.4 KiB +177 B	43.8 KiB +112 B	▁▁▁▅▅▆▆▆▅▆▆█
`solid-start.full`	51.2 KiB +58 B	51.1 KiB +58 B	153.3 KiB +177 B	45.3 KiB +25 B	▁▁▁▅▅▆▆▆▅▆▆█
`vue-start.minimal`	65.7 KiB +53 B	65.6 KiB +54 B	189.7 KiB +177 B	58.5 KiB +11 B	▁▁▁▅▅▆▆▆▅▆▆█
`vue-start.full`	69.6 KiB +53 B	69.4 KiB +52 B	202.0 KiB +177 B	61.7 KiB -26 B	▁▁▁▅▅▆▆▆▅▆▆█

Current gzip tracks all emitted client JS chunks. Initial gzip tracks only the entry/import graph. Trend sparkline is historical current gzip ending with this PR measurement; lower is better.

github-actions · 2026-08-21T22:08:34Z

🚀 Changeset Version Preview

4 package(s) bumped directly, 19 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
`@tanstack/react-router`	1.170.31 → 1.170.32	Changeset
`@tanstack/router-core`	1.171.26 → 1.171.27	Changeset
`@tanstack/solid-router`	1.170.29 → 1.170.30	Changeset
`@tanstack/vue-router`	1.170.28 → 1.170.29	Changeset
`@tanstack/react-start`	1.168.48 → 1.168.49	Dependent
`@tanstack/react-start-client`	1.168.29 → 1.168.30	Dependent
`@tanstack/react-start-rsc`	0.1.47 → 0.1.48	Dependent
`@tanstack/react-start-server`	1.167.36 → 1.167.37	Dependent
`@tanstack/router-cli`	1.167.32 → 1.167.33	Dependent
`@tanstack/router-generator`	1.167.32 → 1.167.33	Dependent
`@tanstack/router-plugin`	1.168.34 → 1.168.35	Dependent
`@tanstack/router-vite-plugin`	1.167.34 → 1.167.35	Dependent
`@tanstack/solid-start`	1.168.46 → 1.168.47	Dependent
`@tanstack/solid-start-client`	1.168.28 → 1.168.29	Dependent
`@tanstack/solid-start-server`	1.167.35 → 1.167.36	Dependent
`@tanstack/start-client-core`	1.170.26 → 1.170.27	Dependent
`@tanstack/start-plugin-core`	1.171.38 → 1.171.39	Dependent
`@tanstack/start-server-core`	1.169.30 → 1.169.31	Dependent
`@tanstack/start-static-server-functions`	1.167.31 → 1.167.32	Dependent
`@tanstack/start-storage-context`	1.167.28 → 1.167.29	Dependent
`@tanstack/vue-start`	1.168.45 → 1.168.46	Dependent
`@tanstack/vue-start-client`	1.167.31 → 1.167.32	Dependent
`@tanstack/vue-start-server`	1.167.35 → 1.167.36	Dependent

nx-cloud · 2026-08-21T22:33:35Z

View your CI Pipeline Execution ↗ for commit 61d058f

Command	Status	Duration	Result
`nx affected --targets=test:eslint,test:unit,tes...`	✅ Succeeded	10m 54s	View ↗
`nx run-many --target=build --exclude=examples/*...`	✅ Succeeded	29s	View ↗

☁️ Nx Cloud last updated this comment at 2026-08-22 06:10:56 UTC

pkg-pr-new · 2026-08-21T22:34:54Z

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commit: 61d058f

codspeed-hq · 2026-08-21T22:52:32Z

Merging this PR will regress 8 benchmarks

⚠️

Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 8 improved benchmarks
❌ 8 regressed benchmarks
✅ 164 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Memory	`mem client unique-location-churn (solid)`	265.7 KB	643.2 KB	-58.69%
❌	Memory	`mem server error-paths redirect (solid)`	382.2 KB	659.7 KB	-42.06%
❌	Memory	`mem client navigation-churn (solid)`	592.5 KB	707.5 KB	-16.24%
❌	Memory	`mem client unique-location-churn (vue)`	467.7 KB	523.6 KB	-10.68%
❌	Memory	`mem server peak-large-page (vue)`	1 MB	1.1 MB	-10.68%
❌	Memory	`mem client interrupted-navigations (vue)`	368.7 KB	394.4 KB	-6.52%
❌	Memory	`mem server error-paths unmatched (solid)`	559.8 KB	588.1 KB	-4.81%
❌	Memory	`mem server server-fn-churn (react)`	378.9 KB	393.5 KB	-3.72%
⚡	Memory	`mem server error-paths not-found (vue)`	2,304.3 KB	481.3 KB	×4.8
⚡	Memory	`mem server error-paths unmatched (react)`	544.1 KB	487.4 KB	+11.63%
⚡	Memory	`mem server aborted-requests (vue)`	1,110.1 KB	1,013.7 KB	+9.52%
⚡	Memory	`mem server error-paths not-found (react)`	423.7 KB	401.2 KB	+5.62%
⚡	Memory	`mem server serialization-payload (vue)`	4.5 MB	4.3 MB	+4.79%
⚡	Memory	`mem server peak-large-page (react)`	1.2 MB	1.2 MB	+4.5%
⚡	Memory	`mem client navigation-churn (vue)`	1.6 MB	1.6 MB	+4.11%
⚡	Memory	`mem server request-churn (vue)`	848.2 KB	816.6 KB	+3.87%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

_{Comparing perf/task4-parallel-head-scripts (61d058f) with main (d83a896)}

Sheraff · 2026-08-22T09:50:16Z

Superseded by #8151, which contains only the route asset parallelization. The independent byte-reduction changes were split into #8150. Both target main.

perf(router-core): evaluate head/scripts across matches in parallel

c114198

github-actions Bot added the package: router-core label Aug 21, 2026

Merge branch 'main' into perf/task4-parallel-head-scripts

61d058f

Sheraff closed this Aug 22, 2026

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perf(router-core): evaluate head/scripts across matches in parallel - #8145

perf(router-core): evaluate head/scripts across matches in parallel#8145
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Sheraff commented Aug 21, 2026

Summary

Behavioral equivalence (strict)

Performance

Verification

Residual risks (documented in RESULT-perf-task4.md)

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🚀 Changeset Version Preview

🟩 Patch bumps

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Merging this PR will regress 8 benchmarks

Performance Changes

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