Framework semantic default

Next.js route handler searchParams request.nextUrl.searchParams docs

A route returns undefined or throws only on the new major.

Next.jsWeb frameworkFramework semantic defaultnext16

Agent Quick Fix

Repair against the current Next.js contract, then keep the change narrow and source-backed.

Product: Next.js
Current-contract area: Next.js 16 route handler reads searchParams synchronously
Likely root cause: A route returns undefined or throws only on the new major.
Repair direction: Verifier checks behavior across multiple requests/build modes, not merely compilation. Check request count, response freshness, and render behavior over multiple calls.

Symptom

A route returns undefined or throws only on the new major.

Why This Happens

Local code often type-checks under both old and new framework semantics; the failure depends on the installed framework version and current runtime defaults.

Common Wrong Fixes

Changing local code without checking the current external contract.
Retrying the same install, build, or API call with no version/source change.
Applying a broad unsafe bypass when a narrow compatibility fix is available.

Codex Search Keywords

These are the search terms observed in a neutral Codex validation run for this failure shape.

site:nextjs.org/docs Next.js 16 route handler searchParams synchronous request searchParams
Next.js route handler searchParams request.nextUrl.searchParams docs
https://nextjs.org/docs/app/api-reference/file-conventions/route
'URL Query Parameters' in https://nextjs.org/docs/app/api-reference/file-conventions/route
https://nextjs.org/docs/app/guides/upgrading/version-15
https://nextjs.org/docs/app/guides/upgrading/version-16