fix(react-router): isolate client-only match hydration

[Sheraff]

Stacked on #8183.

Summary

• keep reactive match-store subscriptions below the ClientOnly hydration gate for ssr: false and data-only routes
• preserve route error and not-found ownership for the pre-hydration pending fallback and the post-hydration reactive match tree
• add focused hydration boundary coverage and a patch changeset

Why

During React 18 hydration, the initial client load can synchronously publish transient match fetching state. A full-match subscription above a dehydrated client-only subtree invalidates that Suspense boundary before hydration completes, producing React error #421.

The match subscription now mounts only in the live MatchInner branch. The pre-hydration fallback uses the same route-boundary construction without subscribing to match updates, while Transitioner remains the sole loading authority.

Closes #8180.

Verification

• CI=1 NX_DAEMON=false pnpm nx run @tanstack/react-router:test:unit --outputStyle=stream --skipRemoteCache
• CI=1 NX_DAEMON=false pnpm nx run @tanstack/react-router:test:types --outputStyle=stream --skipRemoteCache
• CI=1 NX_DAEMON=false pnpm nx run @tanstack/react-router:test:eslint --outputStyle=stream --skipRemoteCache
• React 18 beforeLoad reproduction: 3/3 passing
• React 18 loader reproduction: 3/3 passing

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View your CI Pipeline Execution ↗ for commit 836a97b

Command	Status	Duration	Result
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---

☁️ Nx Cloud last updated this comment at 2026-08-28 08:09:46 UTC

[github-actions]

🚀 Changeset Version Preview

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

🟩 Patch bumps

Package	Version	Reason
@tanstack/react-router	1.170.32 → 1.170.33	Changeset
@tanstack/react-start	1.168.49 → 1.168.50	Dependent
@tanstack/react-start-client	1.168.30 → 1.168.31	Dependent
@tanstack/react-start-rsc	0.1.48 → 0.1.49	Dependent
@tanstack/react-start-server	1.167.37 → 1.167.38	Dependent

[github-actions]

Bundle Size Benchmarks

• Commit: 32107ffa5f27
• Measured at: 2026-08-28T07:55:06.416Z
• Baseline source: history:0caf6b9a2b7e
• 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	83.8 KiB +50 B	83.7 KiB +50 B	262.6 KiB +395 B	73.0 KiB -20 B	██▃▃▃▃▃▃▃▃▁▆
react-router.full	87.3 KiB +37 B	87.2 KiB +34 B	274.3 KiB +396 B	75.9 KiB -46 B	██▃▃▃▃▃▃▃▃▁▅
solid-router.minimal	33.1 KiB +12 B	33.0 KiB +13 B	96.3 KiB +72 B	29.9 KiB -14 B	██▂▂▂▂▂▂▂▂▁▂
solid-router.full	38.0 KiB +16 B	37.9 KiB +11 B	111.0 KiB +72 B	34.2 KiB +34 B	██▂▂▃▃▃▃▃▃▁▃
vue-router.minimal	49.5 KiB +10 B	49.4 KiB +8 B	138.3 KiB +72 B	44.6 KiB -5 B	██▂▂▂▂▂▂▂▂▁▂
vue-router.full	55.1 KiB +8 B	55.0 KiB +9 B	156.6 KiB +72 B	49.5 KiB -38 B	██▁▁▂▂▂▂▂▂▁▂
react-start.minimal	96.7 KiB +34 B	96.6 KiB +34 B	304.8 KiB +397 B	83.8 KiB -5 B	██▃▃▄▄▄▄▄▄▁▅
react-start.deferred-hydration	97.4 KiB +36 B	96.6 KiB +34 B	306.2 KiB +397 B	84.5 KiB +108 B	██▃▃▄▄▄▄▄▄▁▅
react-start.full	99.9 KiB +39 B	99.7 KiB +37 B	314.6 KiB +397 B	86.6 KiB +39 B	██▃▃▄▄▄▄▄▄▁▅
react-start.rsbuild.minimal	100.0 KiB +61 B	99.9 KiB +61 B	315.2 KiB +397 B	86.3 KiB +53 B	██▃▃▄▄▄▄▄▄▁▇
react-start.rsbuild.minimal-iife	100.4 KiB +62 B	100.3 KiB +62 B	316.1 KiB +397 B	86.7 KiB -28 B	██▃▃▄▄▄▄▄▄▁▇
react-start.rsbuild.full	103.4 KiB +62 B	103.2 KiB +62 B	325.2 KiB +397 B	89.0 KiB +42 B	██▃▃▃▃▃▃▃▃▁▇
solid-start.minimal	46.0 KiB +13 B	45.9 KiB +11 B	137.4 KiB +72 B	40.9 KiB +16 B	██▃▃▂▂▂▂▂▂▁▂
solid-start.deferred-hydration	49.1 KiB +9 B	45.9 KiB +10 B	144.9 KiB +72 B	43.7 KiB -2 B	██▂▂▂▂▂▂▂▂▁▂
solid-start.full	51.1 KiB +9 B	51.0 KiB +9 B	152.8 KiB +72 B	45.3 KiB -101 B	██▂▂▂▂▂▂▂▂▁▂
vue-start.minimal	65.6 KiB +14 B	65.5 KiB +10 B	189.2 KiB +72 B	58.4 KiB +67 B	██▁▁▃▃▃▃▃▃▁▃
vue-start.full	69.5 KiB +15 B	69.3 KiB +12 B	201.5 KiB +72 B	61.6 KiB -83 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.

[pkg-pr-new]

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commit: 836a97b

[codspeed-hq]

Merging this PR will degrade performance by 7.38%

⚠️ 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

⚡ 11 improved benchmarks
❌ 9 regressed benchmarks
✅ 160 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Memory	mem server error-paths not-found (vue)	504.3 KB	2,202.7 KB	-77.1%
❌	Memory	mem server error-paths not-found (solid)	551 KB	798.8 KB	-31.02%
❌	Memory	mem server error-paths unmatched (solid)	561.7 KB	628.5 KB	-10.63%
❌	Memory	mem server error-paths redirect (solid)	350 KB	383.4 KB	-8.71%
❌	Memory	mem client unique-location-churn (vue)	429.3 KB	460.7 KB	-6.82%
❌	Memory	mem server aborted-requests (solid)	1.2 MB	1.2 MB	-5.91%
❌	Memory	mem server server-fn-churn (react)	372.6 KB	393.5 KB	-5.32%
❌	Memory	mem server error-paths unmatched (vue)	596.5 KB	626.2 KB	-4.74%
❌	Memory	mem client loader-data-retention (solid)	157.9 KB	162.8 KB	-3.01%
⚡	Simulation	client-async-pipeline navigation loop (react)	65 ms	57.5 ms	+13.16%
⚡	Memory	mem server request-churn (react)	701.4 KB	639.6 KB	+9.65%
⚡	Memory	mem server peak-large-page (solid)	1.2 MB	1.1 MB	+8.55%
⚡	Memory	mem client preload-churn (react)	813.6 KB	753.3 KB	+8%
⚡	Memory	mem client interrupted-navigations (vue)	380.2 KB	353.9 KB	+7.41%
⚡	Memory	mem server peak-large-page (vue)	1.1 MB	1 MB	+7.31%
⚡	Memory	mem server aborted-requests (vue)	1,087.3 KB	1,014.3 KB	+7.2%
⚡	Simulation	ssr global-mw document (vue)	630.7 ms	590.4 ms	+6.82%
⚡	Memory	mem server server-fn-churn (vue)	355.7 KB	339.3 KB	+4.86%
⚡	Simulation	ssr global-mw document (solid)	364.8 ms	349.4 ms	+4.4%
⚡	Memory	mem client navigation-churn (solid)	638 KB	614.5 KB	+3.82%

Tip

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

---

_{Comparing fix/issue-8180-hydration-boundary (836a97b) with main (0caf6b9)¹}

Footnotes

1. No successful run was found on repro/issue-8180 (bf79316) during the generation of this report, so main (0caf6b9) was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩