perf(router-core): skip impossible JSON parse attempts

[Sheraff]

What changed

• avoid calling JSON.parse when a string's first character cannot begin valid JSON
• apply the shortcut only when the configured parser is exactly JSON.parse
• preserve custom parser behavior and all valid JSON prefixes, including whitespace, quotes, numbers, literals, arrays, and objects
• add correctness cases and a focused benchmark covering expected and unfavorable distributions

Why

The default search serializer probes every string with JSON.parse so JSON-looking strings remain strings after a round trip. Ordinary application strings usually fail that probe, making exception creation and handling the dominant cost. The grammar check avoids only parses that are guaranteed to fail.

Impact

Focused local benchmarks, each serializing 1,000 objects:

• ordinary strings: 15.694 ms to 4.571 ms (about 70.9% faster)
• mixed application values: 4.669 ms to 0.482 ms (about 89.7% faster)
• JSON-compatible strings remain on the parse path (0.863 ms in the latest control run)
• strings beginning with JSON literal prefixes remain an intentionally unfavorable control (17.122 ms)

react-router.minimal changes from 85,919 to 85,956 bytes gzip (+37 bytes).

Validation

• @tanstack/router-core:test:unit: 105 files / 1,547 tests passed, plus 3 expected failures
• @tanstack/router-core:test:types: TypeScript 5.6 through 7.0 passed
• @tanstack/router-core:test:eslint: zero errors (existing warnings remain)
• focused tests/searchParams.bench.ts run
• react-router.minimal bundle-size scenario on main and this branch
• git diff --check

Summary by CodeRabbit

• Bug Fixes

  • Improved search-parameter serialization by skipping unnecessary JSON parsing for strings that cannot contain valid JSON.
  • Preserved correct handling of JSON-compatible values, empty strings, punctuation, and custom parsers.

• Performance

  • Reduced avoidable parsing work during query-string serialization.

• Tests

  • Expanded coverage for serialization edge cases.
  • Added benchmarks for representative search-parameter scenarios.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 3ce06239-1eef-4f84-9e31-3c0ad504f4c5

📥 Commits

Reviewing files that changed from the base of the PR and between c568caf and e86a0d5.

📒 Files selected for processing (4)

• .changeset/dirty-bushes-sink.md
• packages/router-core/src/searchParams.ts
• packages/router-core/tests/searchParams.bench.ts
• packages/router-core/tests/searchParams.test.ts

---

📝 Walkthrough

Walkthrough

The search parameter serializer now avoids impossible JSON.parse calls by checking string prefixes. Tests and benchmarks cover default serialization, custom parsers, JSON-compatible strings, and edge cases. A patch changeset documents the router-core update.

Changes

Search serialization

Layer / File(s)	Summary
Guard JSON parsing packages/router-core/src/searchParams.ts	stringifyValue checks jsonStart and the exact JSON.parse function before parsing string values.
Validate serialization behavior packages/router-core/tests/searchParams.test.ts, packages/router-core/tests/searchParams.bench.ts, .changeset/dirty-bushes-sink.md	Tests and benchmarks cover ordinary values, JSON-compatible strings, custom parsers, punctuation, empty strings, and mixed values. The changeset marks a patch release.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant stringifySearchWith
  participant stringifyValue
  participant JSON.parse
  stringifySearchWith->>stringifyValue: serialize search value
  stringifyValue->>stringifyValue: check jsonStart
  stringifyValue->>JSON.parse: parse eligible string
  JSON.parse-->>stringifyValue: parsed value
  stringifyValue-->>stringifySearchWith: serialized value

Loading

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main optimization: skipping impossible JSON parse attempts in router-core.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch agent/search-params-skip-json-parse

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[nx-cloud]

View your CI Pipeline Execution ↗ for commit e86a0d5

Command	Status	Duration	Result
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---

☁️ Nx Cloud last updated this comment at 2026-08-08 17:21:40 UTC

[github-actions]

🚀 Changeset Version Preview

1 package(s) bumped directly, 22 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
@tanstack/router-core	1.171.19 → 1.171.20	Changeset
@tanstack/react-router	1.170.23 → 1.170.24	Dependent
@tanstack/react-start	1.168.40 → 1.168.41	Dependent
@tanstack/react-start-client	1.168.21 → 1.168.22	Dependent
@tanstack/react-start-rsc	0.1.39 → 0.1.40	Dependent
@tanstack/react-start-server	1.167.28 → 1.167.29	Dependent
@tanstack/router-cli	1.167.25 → 1.167.26	Dependent
@tanstack/router-generator	1.167.25 → 1.167.26	Dependent
@tanstack/router-plugin	1.168.27 → 1.168.28	Dependent
@tanstack/router-vite-plugin	1.167.27 → 1.167.28	Dependent
@tanstack/solid-router	1.170.22 → 1.170.23	Dependent
@tanstack/solid-start	1.168.39 → 1.168.40	Dependent
@tanstack/solid-start-client	1.168.21 → 1.168.22	Dependent
@tanstack/solid-start-server	1.167.28 → 1.167.29	Dependent
@tanstack/start-client-core	1.170.19 → 1.170.20	Dependent
@tanstack/start-plugin-core	1.171.31 → 1.171.32	Dependent
@tanstack/start-server-core	1.169.23 → 1.169.24	Dependent
@tanstack/start-static-server-functions	1.167.24 → 1.167.25	Dependent
@tanstack/start-storage-context	1.167.21 → 1.167.22	Dependent
@tanstack/vue-router	1.170.21 → 1.170.22	Dependent
@tanstack/vue-start	1.168.38 → 1.168.39	Dependent
@tanstack/vue-start-client	1.167.24 → 1.167.25	Dependent
@tanstack/vue-start-server	1.167.28 → 1.167.29	Dependent

[github-actions]

Bundle Size Benchmarks

• Commit: efb9dfc55201
• Measured at: 2026-08-08T17:17:34.467Z
• Baseline source: history:c568caf3f376
• Dashboard: bundle-size history

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

Scenario	Current (gzip)	Delta vs baseline	Initial gzip	Raw	Brotli	Trend
react-router.minimal	83.92 KiB	+17 B (+0.02%)	83.78 KiB	262.67 KiB	72.99 KiB	█████████▁▁▁
react-router.full	87.43 KiB	+34 B (+0.04%)	87.29 KiB	274.39 KiB	76.15 KiB	█████████▁▁▁
solid-router.minimal	33.24 KiB	+25 B (+0.07%)	33.12 KiB	96.51 KiB	29.94 KiB	█████████▁▁▁
solid-router.full	38.07 KiB	+27 B (+0.07%)	37.95 KiB	111.14 KiB	34.25 KiB	█████████▁▁▁
vue-router.minimal	49.53 KiB	+36 B (+0.07%)	49.41 KiB	138.25 KiB	44.68 KiB	█████████▁▁▁
vue-router.full	55.11 KiB	+39 B (+0.07%)	54.99 KiB	156.43 KiB	49.59 KiB	█████████▁▁▁
react-start.minimal	96.70 KiB	+41 B (+0.04%)	96.57 KiB	304.83 KiB	83.82 KiB	█████████▁▁▁
react-start.deferred-hydration	97.44 KiB	+51 B (+0.05%)	96.59 KiB	306.19 KiB	84.42 KiB	█████████▁▁▁
react-start.full	99.88 KiB	+50 B (+0.05%)	99.75 KiB	314.55 KiB	86.52 KiB	█████████▁▁▁
react-start.rsbuild.minimal	100.02 KiB	+25 B (+0.02%)	99.85 KiB	315.37 KiB	86.20 KiB	▁▁▁▆▆▅▅▆▆▆▆█
react-start.rsbuild.minimal-iife	100.42 KiB	+22 B (+0.02%)	100.26 KiB	316.31 KiB	86.58 KiB	▁▁▁▆▆▅▅▆▆▆▆█
react-start.rsbuild.full	103.35 KiB	+34 B (+0.03%)	103.17 KiB	325.46 KiB	88.99 KiB	▁▁▁▅▅▄▄▆▆▆▆█
solid-start.minimal	45.97 KiB	+31 B (+0.07%)	45.85 KiB	137.51 KiB	40.93 KiB	█████████▁▁▁
solid-start.deferred-hydration	49.04 KiB	+37 B (+0.07%)	45.90 KiB	144.97 KiB	43.65 KiB	█████████▁▁▁
solid-start.full	51.05 KiB	+37 B (+0.07%)	50.93 KiB	152.90 KiB	45.29 KiB	█████████▁▁▁
vue-start.minimal	65.52 KiB	+31 B (+0.05%)	65.39 KiB	189.02 KiB	58.38 KiB	█████████▁▁▁
vue-start.full	69.34 KiB	+55 B (+0.08%)	69.21 KiB	201.30 KiB	61.58 KiB	█████████▁▁▁

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.

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commit: e86a0d5

[codspeed-hq]

Merging this PR will degrade performance by 0.36%

⚠️ 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

⚡ 23 improved benchmarks
❌ 7 (👁 7) regressed benchmarks
✅ 150 untouched benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Memory	mem server error-paths redirect (solid)	588.2 KB	288.5 KB	×2
⚡	Simulation	ssr request loop (react)	80 ms	51.8 ms	+54.26%
⚡	Simulation	client-search-params navigation loop (react)	59.4 ms	47.1 ms	+26.14%
⚡	Simulation	ssr rewrite localized (react)	89 ms	75.3 ms	+18.2%
⚡	Simulation	client-search-params navigation loop (vue)	80.5 ms	68.4 ms	+17.63%
⚡	Simulation	client-links navigation loop (react)	90.6 ms	77.2 ms	+17.41%
⚡	Simulation	client-search-params navigation loop (solid)	114.8 ms	99.9 ms	+14.93%
⚡	Simulation	ssr request loop (solid)	158 ms	144.4 ms	+9.41%
⚡	Simulation	ssr rewrite passthrough (react)	114.1 ms	104.6 ms	+9.08%
⚡	Simulation	client-links navigation loop (vue)	163.9 ms	150.5 ms	+8.92%
⚡	Simulation	ssr rewrite localized (solid)	126.6 ms	117 ms	+8.17%
⚡	Simulation	client-side navigation loop (react)	41.2 ms	38.1 ms	+8.05%
⚡	Simulation	ssr request loop (vue)	270.2 ms	254.9 ms	+6%
⚡	Memory	mem client preload-churn (vue)	776.2 KB	735.3 KB	+5.57%
⚡	Simulation	client-rewrites navigation loop (react)	44.6 ms	42.4 ms	+5.21%
⚡	Simulation	client-rewrites navigation loop (vue)	48.1 ms	45.9 ms	+4.77%
⚡	Simulation	client-side navigation loop (vue)	70.1 ms	67 ms	+4.6%
⚡	Simulation	client-side navigation loop (solid)	88 ms	84.4 ms	+4.26%
⚡	Simulation	ssr rewrite localized (vue)	214.6 ms	206.9 ms	+3.74%
⚡	Memory	mem server serialization-payload (solid)	3.5 MB	3.4 MB	+3.51%
...	...	...	...	...	...

ℹ️ Only the first 20 benchmarks are displayed. Go to the app to view all benchmarks.

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing agent/search-params-skip-json-parse (e86a0d5) with main (c568caf)}