fix(react-router): avoid rewriting unchanged head assets by schiller-manuel · Pull Request #8257 · TanStack/router

schiller-manuel · 2026-09-05T21:50:03Z

🎯 Changes

React 19 rewrites unchanged head content when dangerouslySetInnerHTML gets a new object. This replaces the stylesheet during navigation and can fail under Trusted Types.

Memoize HTML payloads for styles and data scripts.
Extend the existing inline-CSS e2e fixture with native DOM/CSSOM assertions and enforced-CSP navigation coverage for Vite and Rsbuild. No setter patches or permissive policies.
Use native script lookup and URL resolution to offset the added code. Keep server guards directly in conditionals for dead-code elimination.

This prevents redundant writes after hydration, but does not add general Trusted Types support.

All 18 bundle scenarios match or improve the primary gzip metric against origin/main: eight shrink by 19-31 bytes. Raw output shrinks by 47 bytes in affected scenarios. Brotli increases by 57-175 bytes in five scenarios.

Fixes#8250

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested code changes locally with the relevant test commands, or tests do not apply to this pull request.
I fully understand the code in this pull request, including any code generated with AI assistance.

🚀 Release Impact

This change affects published code, and I have generated a changeset.
This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

Bug Fixes
- Prevented unnecessary rewrites of unchanged inline styles and scripts during React re-renders.
- Improved client navigation compatibility with Trusted Types policies, avoiding related security errors.
- Preserved inline stylesheets across route changes, reducing unnecessary CSS processing.
- Prevented duplicate external and inline scripts from being added during navigation.
- Ensured asset content and DOM elements remain stable when rendered content has not changed.

Fixes#8250 Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

coderabbitai · 2026-09-05T21:50:59Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Team

Run ID: 86ae3a32-a58b-4459-89e4-41457e76fc9c

📥 Commits

Reviewing files that changed from the base of the PR and between 0497cae and 2e38f88.

📒 Files selected for processing (5)

.changeset/spotty-poems-smell.md
e2e/react-start/css-inline/src/routes/app/dashboard/index.tsx
e2e/react-start/css-inline/tests/css-inline.spec.ts
packages/react-router/src/Asset.tsx
packages/react-router/tests/Asset.test.tsx

Included review availability: Your plan provides up to 10 included reviews per hour; 6 remain after this review.

📝 Walkthrough

Walkthrough

Asset now memoizes dangerouslySetInnerHTML values and improves script deduplication. Unit and end-to-end tests cover rerenders, navigation, stylesheet stability, script reuse, and Trusted Types enforcement.

Changes

Asset rendering and navigation

Layer / File(s)	Summary
Stable HTML and script deduplication `packages/react-router/src/Asset.tsx`	Memoized HTML objects prevent unchanged style and script content from being rewritten. Script detection now scans `document.scripts` and separates external and inline scripts.
Asset regression tests `packages/react-router/tests/Asset.test.tsx`	Tests cover stable DOM nodes, script attributes, cleanup, external script reuse, and inline-script deduplication.
Navigation and release validation `e2e/react-start/css-inline/src/routes/app/dashboard/index.tsx`, `e2e/react-start/css-inline/tests/css-inline.spec.ts`, `.changeset/spotty-poems-smell.md`	End-to-end tests verify stylesheet identity, zero mutations, and navigation without Trusted Types violations or browser errors. The changeset records a patch release.
Estimated code review effort: 3 (Moderate)	~25 minutes

Merge Risk:⚪ Minimal · up to 2e38f

This change stabilizes unchanged inline style and script content across navigation, preventing redundant browser writes and Trusted Types failures. The included regression coverage supports merge readiness.

Sequence Diagram(s)

sequenceDiagram
participant React19
participant Asset
participant DOM
participant Browser
React19->>Asset: rerender route assets
Asset->>React19: provide memoized HTML object
React19->>DOM: retain unchanged style or script content
Asset->>Browser: inspect existing scripts
Browser-->>Asset: return matching script elements
Asset->>DOM: reuse or inject script

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 4 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the primary change: preventing rewrites of unchanged React Router head assets.
Description check	✅ Passed	The description follows the required template, explains the change and motivation, documents testing and release impact, and includes the required changeset information.
Linked Issues check	✅ Passed	The implementation addresses issue `#8250` by memoizing HTML payloads for styles and data scripts. The added unit and end-to-end tests verify unchanged assets are not rewritten and that enforced Trusted…
Out of Scope Changes check	✅ Passed	All changes are related to issue `#8250` and the stated objectives. The source fix, regression tests, end-to-end coverage, and changeset are in scope.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 4 files. (1 skipped: 1 unsupported.)

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✨ Finishing Touches 💡 1

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Create PR with unit tests
Commit unit tests in branch schiller-manuel-head-asset-stability

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github-actions · 2026-09-05T21:53:27Z

🚀 Changeset Version Preview

6 package(s) bumped directly, 18 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
`@tanstack/nitro-v2-vite-plugin`	1.155.0 → 1.155.1	Changeset
`@tanstack/react-router`	1.170.32 → 1.170.33	Changeset
`@tanstack/router-core`	1.171.27 → 1.171.28	Changeset
`@tanstack/solid-router`	1.170.30 → 1.170.31	Changeset
`@tanstack/start-plugin-core`	1.171.39 → 1.171.40	Changeset
`@tanstack/vue-router`	1.170.29 → 1.170.30	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
`@tanstack/router-cli`	1.167.33 → 1.167.34	Dependent
`@tanstack/router-generator`	1.167.33 → 1.167.34	Dependent
`@tanstack/router-plugin`	1.168.35 → 1.168.36	Dependent
`@tanstack/router-vite-plugin`	1.167.35 → 1.167.36	Dependent
`@tanstack/solid-start`	1.168.47 → 1.168.48	Dependent
`@tanstack/solid-start-client`	1.168.29 → 1.168.30	Dependent
`@tanstack/solid-start-server`	1.167.36 → 1.167.37	Dependent
`@tanstack/start-client-core`	1.170.27 → 1.170.28	Dependent
`@tanstack/start-server-core`	1.169.31 → 1.169.32	Dependent
`@tanstack/start-static-server-functions`	1.167.32 → 1.167.33	Dependent
`@tanstack/start-storage-context`	1.167.29 → 1.167.30	Dependent
`@tanstack/vue-start`	1.168.46 → 1.168.47	Dependent
`@tanstack/vue-start-client`	1.167.32 → 1.167.33	Dependent
`@tanstack/vue-start-server`	1.167.36 → 1.167.37	Dependent

nx-cloud · 2026-09-05T21:56:21Z

View your CI Pipeline Execution ↗ for commit 2e38f88

Command	Status	Duration	Result
`nx affected --targets=test:eslint,test:unit,tes...`	✅ Succeeded	15m 9s	View ↗
`nx run-many --target=build --exclude=examples/*...`	✅ Succeeded	2m 3s	View ↗

☁️ Nx Cloud last updated this comment at 2026-09-05 22:12:40 UTC

github-actions · 2026-09-05T21:59:38Z

Bundle Size Benchmarks

Commit: 51406bc3813b
Measured at: 2026-09-05T21:53:32.298Z
Baseline source: history:0497caeef3ff
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.full`	87.2 KiB -31 B	87.1 KiB -31 B	273.7 KiB -47 B	76.0 KiB -36 B	██▂▅▅▆▆▆▆▆▆▁
`react-start.minimal`	96.7 KiB -19 B	96.5 KiB -18 B	304.3 KiB -47 B	83.8 KiB -13 B	▇█▁▅▇▆▅▇▇▇▅▂
`react-start.query-integration`	104.0 KiB -28 B	103.9 KiB -31 B	330.8 KiB -47 B	90.2 KiB +70 B	▆▇▁▄▅▅▅▅▅▅█▄
`react-start.deferred-hydration`	97.4 KiB -25 B	96.5 KiB -20 B	305.6 KiB -47 B	84.5 KiB +67 B	▇█▁▃▆▆▅▆▆▆█▃
`react-start.full`	99.8 KiB -23 B	99.7 KiB -24 B	314.0 KiB -47 B	86.4 KiB -28 B	▇█▁▅▆▇▆▆▆▆█▄
`react-start.rsbuild.minimal`	100.0 KiB -29 B	99.8 KiB -29 B	314.6 KiB -47 B	86.3 KiB +175 B	██▁▄▃▃▂▃▃▃█▃
`react-start.rsbuild.minimal-iife`	100.4 KiB -24 B	100.2 KiB -24 B	315.5 KiB -47 B	86.7 KiB +89 B	██▁▃▃▃▂▃▃▃▇▃
`react-start.rsbuild.full`	103.3 KiB -23 B	103.1 KiB -23 B	324.7 KiB -47 B	89.0 KiB +57 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 · 2026-09-05T22:01:05Z

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commit: 2e38f88

codspeed-hq · 2026-09-05T22:21:12Z

Merging this PR will regress 4 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

⚡ 9 improved benchmarks
❌ 4 regressed benchmarks
✅ 167 untouched benchmarks
⏩ 48 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Memory	`mem server aborted-requests (vue)`	1,014.4 KB	1,110.8 KB	-8.68%
❌	Memory	`mem server error-paths redirect (react)`	316.6 KB	334.2 KB	-5.26%
❌	Memory	`mem server server-fn-churn (vue)`	345.8 KB	364.7 KB	-5.18%
❌	Memory	`mem server server-fn-churn (react)`	409.2 KB	423.2 KB	-3.31%
⚡	Memory	`mem server error-paths redirect (vue)`	454.2 KB	410.9 KB	+10.53%
⚡	Memory	`mem server error-paths not-found (react)`	450.3 KB	408.5 KB	+10.21%
⚡	Memory	`mem client unique-location-churn (solid)`	409.6 KB	385.1 KB	+6.36%
⚡	Memory	`mem client mount-unmount (solid)`	511 KB	482.3 KB	+5.94%
⚡	Memory	`mem client interrupted-navigations (vue)`	356.7 KB	340.1 KB	+4.86%
⚡	Memory	`mem server error-paths not-found (vue)`	503.4 KB	482.9 KB	+4.24%
⚡	Memory	`mem server peak-large-page (vue)`	1 MB	1 MB	+3.96%
⚡	Memory	`mem server error-paths not-found (solid)`	772.7 KB	743.4 KB	+3.95%
⚡	Memory	`mem client navigation-churn (vue)`	1.6 MB	1.5 MB	+3.17%

Tip

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

_{Comparing schiller-manuel-head-asset-stability (2e38f88) with main (0497cae)}

48 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. ↩

fix(react-router): avoid rewriting unchanged head assets
2e38f88
Fixes#8250 Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

github-actionsBot added the package: react-router label Sep 5, 2026

schiller-manuel merged commit cf166d1 into mainSep 5, 2026
25 checks passed

schiller-manuel deleted the schiller-manuel-head-asset-stability branch September 5, 2026 22:21

This was referenced Sep 5, 2026
ci: Version Packages #8182
Merged
ci: Version Packages LadyBluenotes/router#2
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fix(react-router): avoid rewriting unchanged head assets - #8257

fix(react-router): avoid rewriting unchanged head assets#8257
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