Environment

• Next.js 14.2.35, hybrid App Router + one Pages Router API route (pages/api/export/pdf.ts — required for react-dom/server, which fails under App Router's react-server condition)
• No output: 'export' in next.config.mjs — no static export configured anywhere in the app

Error Error: ENOENT: no such file or directory, lstat '.next/export-detail.json'

Thrown by Vercel's build step immediately after next build completes successfully.

What I've confirmed

• next build exits 0, both locally and on Vercel's remote builder — all pages and functions listed, no build errors
• .next/export-marker.json is present and correctly reports "hasExportPathMap": false — the app has no static export configured, so export-detail.json shouldn't be expected
• .next/export-detail.json is not produced, consistent with that marker
• Reproduces identically across every variable I could think to test:
  • original project AND a brand-new project created fresh for this test (rules out project-level settings)
  • Node 20.x and Node 24.x
  • remote builder v58.4.0 and local vercel build v53.2.0
  • with/without build cache, with/without .vercelignore, with/without outputFileTracingIncludes in next.config.mjs
  • vercel.json unchanged from a deploy that got past this exact step
• Dashboard Build & Development Settings have no overrides — Framework Preset correctly detected as Next.js, Build Command/Output Directory/Install Command all default

One thing I can't explain myself An earlier deploy on this project did get past this build step (it failed later, on an unrelated function-size limit). I haven't been able to identify what changed since then that would make the builder start expecting this file.

Happy to share a minimal repro repo if that's useful.