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Next Dev Hangs Forever When Module Request Exceeds V8 Regexp Stack Limit In Bundled Enhanced-Resolve

Next.js webpack dev server never resolves requests for modules whose identifiers exceed ~8.39M characters because the vendored enhanced-resolve uses a regex that overflows V8's RegExp stack, throwing RangeError and leaving the compilation promise permanently pending.

highConfidence 95%Next.js Affected V15.5.18 Affected V16.3.1-Canary.16

Origin Analysis

The bundled webpack in next/dist/compiled/webpack/bundle5.js contains an outdated enhanced-resolve whose parseIdentifier function runs the regex /^(#?(?:\0.|[^?#\0])*)(\?(?:\0.|[^#\0])*)?(#.*)?$/ on every module request. For inputs above V8's RegExp stack limit (~8,388,572 chars), RegExp.exec throws RangeError: Maximum call stack size exceeded. The error is emitted as an unhandledRejection, not handled by the dev compiler, so the pending request never resolves.

1. git clone https://github.com/MuzajsArcin/nextjs-dev-hang-repro 2. cd nextjs-dev-hang-repro && npm install 3. node generate.mjs 8388573 # writes src/big.mjs with one 8,388,573-char data: URI 4. npm run dev 5. curl --max-time 60 http://localhost:3247/ -> never responds; dev server prints ○ Compiling / ... and RangeError: Maximum call stack size exceeded

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 is a development-only workaround and should be removed once the bundled enhanced-resolve is updated. It only bypasses the regex for the specific pattern and inputs without null bytes; if a future request contains a null byte and is also extremely large, the original regex path may still overflow. Global monkey-patching RegExp.prototype.exec could theoretically affect other libraries that rely on exact regex execution semantics, but the scope is limited to the target source. To roll back, delete or comment out the patch block in next.config.js and restart the dev server.