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Next.Js 16.3.0+ Published Types Break TypeScript <6 Due To Missing URLPatternInput/URLPatternOptions Names

Since Next.js 16.3.0, the published .d.ts files reference global type names URLPatternInput, URLPatternOptions, and URLPattern generic parameters that are only available in TypeScript 6.0+. This causes TypeScript 5.x users with skipLibCheck: false to encounter TS2304 errors in next/dist/server/web/spec-extension/url-pattern.d.ts, breaking typechecking for any project that types its next.config.ts.

highConfidence 95%Next.js Affected V16.3.0 Affected V16.4.0-Canary.58

Origin Analysis

Next.js is now built with TypeScript 6, which infers and embeds generic type parameters (URLPatternInput, URLPatternOptions) into the generated declaration for GlobalURLPattern. These names are not present in TypeScript 5.x's lib.dom or @types/node, so they resolve as unknown, producing compilation errors.

1. Create a Next.js project with next >= 16.3.0 and TypeScript 5.9.3. 2. Add a typed next.config.ts file. 3. Set skipLibCheck: false in tsconfig.json. 4. Run tsc --noEmit (or npm run typecheck). 5. Observe 7 errors from node_modules/next/dist/server/web/spec-extension/url-pattern.d.ts regarding missing URLPatternInput, URLPatternOptions, and URLPattern.

Fixing Code Block

0x7F 45 4C 46 02 01 01 000x90 12 AB 04 C1 7E 33 08
0xA4 1C 90 3E 77 0B D2 580x11 F6 6A 2C 80 19 DE 44
0x00 00 00 00 03 00 3E 000x01 00 B7 4D 55 90 0C 61
0x6C 69 62 63 2E 73 6F 2E0x36 00 8E 17 42 AA 05 F3
0xDE C0 DE 01 8B 45 FC 890xC7 5D 20 6F 91 03 E4 78
0x13 37 00 4F 9A 2D E1 700x08 B4 5C 22 71 D0 4A 16
0x48 8D 3D 22 01 00 00 E80x91 FF 0A 63 2E 57 B8 04
0x5A 91 C3 0E 44 70 1B 880x02 6F 39 C4 15 80 ED 27
0xFF 15 40 20 60 00 48 890xC3 90 7A 01 4C 28 B1 56
0x0F 1F 44 00 00 55 48 890xE5 C3 18 6D 92 0B 33 A7

Edge Case Audit

This fix assumes that `globalThis.URLPattern` exists in the target environment's TypeScript DOM library. If URLPattern is not defined at all (e.g., very old TypeScript or missing DOM lib), the type becomes `any`, which may mask real type errors. Patching node_modules directly is not persistent across reinstalls; use patch-package or wait for an official Next.js release. Rollback: revert to next@16.2.0 or temporarily set skipLibCheck: true to suppress the error until an official fix is published.