Build failure: Babel flowtype page compilation not supported

This issue was created by an agent analysing CI failures from the Next.js Deploy Suite (vinext main vs Next.js v16.2.6, 2026-05-22).

Problem

Pages using flowtype syntax (compiled via Babel + @babel/preset-flow) fail the vinext build with Custom deploy script failed: undefined (1). The Vite/Rolldown pipeline does not run user Babel configuration for these files.

Babel + preset-flow page fails to build

Estimated Impact

~1 test failures across the deploy suite.

Affected Test Suites

• test/e2e/babel/index.test.ts

Recommendation

1. Reproduce first in vinext's own test suite. Add a page using flow syntax with a .babelrc enabling @babel/preset-flow, confirm the build fails.

2. Decide on Babel support. Either add an opt-in Babel-compatibility loader for files matched by user .babelrc, or document that Babel is not portable and convert the fixture to TS.