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CacheComponents: Runtime ISR Revalidation Throws Message-Less StaticGenBailoutError; Real Reason Only On Console.Error

During background ISR revalidation with cacheComponents enabled, throwIfDisallowedDynamic throws a StaticGenBailoutError with no message or cause. The detailed violation is logged only to console.error via logDisallowedDynamicError, so error trackers receive an empty, unactionable Error event.

highConfidence 87%Next.js Affected V16.2.9

Origin Analysis

throwIfDisallowedDynamic in packages/next/src/server/app-render/dynamic-rendering.ts constructs `new StaticGenBailoutError()` with no arguments after calling logDisallowedDynamicError, discarding the already-computed dynamic violation message. This is a design flaw in the error-surfacing path: the sentinel error carries no diagnostic context, only the synchronous console output does.

1. Configure Next.js 16.2.9 with `cacheComponents: true` and a fully static route. 2. In a section fetcher catch block, trigger disallowed dynamic usage (e.g. `crypto.randomUUID()` via Sentry <10.57.0, or `Date.now()`) during a background ISR revalidation (handleRevalidate). 3. Observe the revalidation abort and the forwarded error in onRequestError: the Error message is empty, minified stack only; the real reason (e.g. "Route ... used `crypto.randomUUID()` ...") appears only in console.error/function logs.

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 change only modifies the message of a thrown sentinel error; rollback is safe with `git revert`. Potential secondary risks: (1) if the dynamic error message contains sensitive route or query information, it may now appear in error trackers; review message content and scrub PII if necessary. (2) Some tests or downstream error-parsing logic may assert on empty messages; update snapshots accordingly. (3) The `dynamicErrors` array may be empty in edge cases; the fallback prevents undefined messages. (4) This does not address the root dynamic violation itself, only its observability.