router fix: Do not parse / stringify search params that are not json objects

By default, the router parses search params using JSON.parse, regardless of whether the param is a JSON object or not. This causes strange behavior, for example, it adds quotes around numerical strings: http://my-app.com?p=123 changes to http://my-app.com?p="123"

It also causes rounding issues when large numbers are converted into integers, for example:

http://my-app.com?p=1000000000000001110 becomes http://my-app.com?p="1000000000000001200"

Which means that resource IDs cannot be used in search params, which I guess is a common use-case.

This PR solves this by not calling the parser on params that are not json objects.

Dec 01 '25 09:12 adbjo

Walkthrough

Parse/stringify logic updated to avoid coercing or replacing raw string values unless a parser returns an object; qss decoding no longer coerces strings to booleans/numbers; tests updated to validate parse-first then stringify roundtrips.

Changes

Cohort / File(s)	Summary
Search params logic `packages/router-core/src/searchParams.ts`	`parseSearchWith` now assigns parser results only when the parser returns an object; `stringifySearchWith` only re-stringifies when the parser returns an object, otherwise original string values are preserved.
Query-string decoding `packages/router-core/src/qss.ts`	Removed the `toValue` coercion helper; `decode` now returns raw string values (and arrays of raw strings) instead of coercing to numbers/booleans.
Tests `packages/router-core/tests/searchParams.test.ts`, `packages/router-core/tests/qss.test.ts`	Tests updated to parse-first then stringify for isomorphism checks; expectations adjusted to reflect raw-string decoding and arrays for repeated keys.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20–30 minutes

Inspect searchParams.ts parser branches for cases where parsers return primitives vs objects.
Verify callers of qss.decode and any consumers expecting coerced numeric/boolean types.
Run unit tests covering repeated keys, empty values, escaped literals, and custom parsers.

Possibly related PRs

TanStack/router#4987 — Touches parse/stringify behavior and tests for default parse/stringify utilities; closely related test and behavior changes.
TanStack/router#5574 — Edits the same parsing/stringifying utilities (docs/JSDoc nearby); relevant to function-level behavior.
TanStack/router#4985 — Modifies qss.ts and searchParams.ts implementations; overlaps with decode/parse behavior adjustments.

Suggested reviewers

schiller-manuel
SeanCassiere

Poem

"I hopped through queries, kept each string intact,
I nudged only objects where parsers interact.
Numbers no longer sneak into string beds,
Roundtrips hum softly as tests nod their heads.
— 🐇"

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%.
Title check	✅ Passed	The title accurately describes the main change: preventing parsing and stringifying of search params that are not JSON objects, which addresses the issue of unwanted quoting of numerical/string parameters.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing touches

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🧪 Generate unit tests (beta)

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[ ] Post copyable unit tests in a comment

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Dec 01 '25 09:12 coderabbitai[bot]

🤖 Nx Cloud AI Fix Eligible

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☁️ Nx Cloud last updated this comment at 2025-12-01 19:37:23 UTC

Dec 01 '25 19:12 nx-cloud[bot]

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commit: 1af0d4b

Dec 01 '25 19:12 pkg-pr-new[bot]

Fixes: https://github.com/TanStack/router/issues/6044

Dec 09 '25 14:12 adbjo