fix(converters): preserve query param encoding in getQueryFromSearchParams

[azuma317]

What

getQueryFromSearchParams parsed query values by iterating over URLSearchParams.entries(), which decodes each value. However, since #817, convertToQueryString intentionally does not re-encode values (it concatenates them raw to preserve their original encoding). This leaves the two sides of the round-trip inconsistent:

• parse (getQueryFromSearchParams) → decoded values
• serialize (convertToQueryString) → assumes already-encoded values, no re-encoding

As a result, any query value containing reserved characters (&, =, +, spaces, …) is corrupted when req.url is rebuilt from the parsed query in requestHandler.ts:

req.url =
  initialURL.pathname +
  convertToQueryString(routingResult.internalEvent.query);

A decoded value such as https://example.com/auth?a=1&b=2 gets concatenated as-is, so the embedded &/= split the outer query string and everything after the first reserved char is lost or reinterpreted as separate params.

Reproduction

This is the root cause of opennextjs/opennextjs-cloudflare#1134. It reliably breaks, for example, Sign in with Apple via better-auth's Expo flow: the client hits …/expo-authorization-proxy?authorizationURL=<percent-encoded URL>, the encoded %26/%3D inside authorizationURL are decoded to &/=, the URL is truncated at the first &, the state param is lost, and the endpoint returns 400 "Unexpected error". It only manifests in production (Workers / any deployment that goes through this req.url reconstruction), not in next dev.

Fix

Keep the parsed values percent-encoded so they round-trip correctly through convertToQueryString. This completes the model established in #817 (query records hold encoded values end-to-end) rather than reverting convertToQueryString — which would reintroduce the double-decode problem #817 fixed and break the existing "should respect existing query encoding" test.

Multi-value grouping and the empty-query case are preserved.

Tests

Added unit tests for getQueryFromSearchParams covering the empty case, single value, repeated-key grouping, and the reserved-character round-trip from #1134. Full unit suite (604 passed), biome check, and tsc --noEmit all pass.

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Latest commit: 6cb2732

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@opennextjs/aws	Patch
app-pages-router	Patch

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commit: 6cb2732