Weird interaction between CJS and ESM for JSON modules, when using yarn

[A5rocks]

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Minimal reproduction URL

I provided the exact source below; I don't have a StackBlitz to upload it there.

Problem & expected behavior (under 200 words)

Make sure to use yarn.

package.lock:

{
  "name": "example",
  "version": "1.0.0",
  "type": "module",
  "packageManager": "yarn@4.14.1",
  "dependencies": {
    "http-errors": "^2.0.1"
  },
  "devDependencies": {
    "@types/http-errors": "^2",
    "tsx": "^4.22.3"
  }
}

src/index.ts:

import { errors } from "./errors.js";

errors;

src/errors.ts:

import { isHttpError } from "http-errors";

export const errors = () => {
  isHttpError;
};

Run:

• yarn install
• yarn tsx src/index.ts

Bugs are expected to be fixed by those affected by it

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[privatenumber]

I looked into this. Root cause: under Yarn PnP on Node 24+, the context.conditions reaching tsx's load hook for a JSON file required via Node's CJS-from-ESM bridge contains 'import' instead of 'require', so tsx's existing detection misses the bridge case and transforms the JSON to ESM shape, breaking the CJS consumer. The conditions mismatch is a known upstream Node bug (nodejs/node#51327, filed Dec 2023, confirmed but stale). The bridge case and a CJS-file dynamic import('./x.json', { with: { type: 'json' } }) arrive byte-identical at the hook — the only reliable signal I could find that tells them apart is Node's internal loadAndTranslateForRequireInImportedCJS frame in the call stack. That's a workable signal for tsx's sync hook path (module.registerHooks, default on Node ≥ 24.11).

It doesn't work for the async hook fallback though: when a .ts file is preloaded before tsx (e.g. node --import ./preload.ts --import tsx ...), tsx uses module.register and hooks run in a worker thread — the bridge frame only exists on the main thread, and Node's async hook context is stripped of conditions and request type entirely (confirmed against v24.15.0 and v26.1.0 source). For now, if you're hitting that combo: use a JS preload instead of .ts.