Regression: executed in ESM scope with "type": "commonjs" in Node 23.6

[abrahamguo]

Acknowledgements

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Minimal reproduction URL

https://github.com/abrahamguo/repro/tree/tsx

Problem & expected behavior (under 200 words)

Running npx tsx index.ts produces

__dirname;
^


ReferenceError: __dirname is not defined in ES module scope
    at <anonymous> (/Users/abraham/PhpstormProjects/repro/index.ts:1:1)
    at ModuleJob.run (node:internal/modules/esm/module_job:272:25)
    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:580:26)
    at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:98:5)

Node.js v23.6.0

demonstrating that tsx is incorrectly executing this script in ESM mode, even though the package.json includes "type": "commonjs".

Making any of the following changes makes the issue go away:

• Switching from Node 23.6 to 23.5. (Type stripping was turned on by default in this release, but I'm not sure if that's the problem: 23.6 changelog)
• Removing "type": "commonjs" from package.json.
• Adding --no-experimental-strip-types.
• Adding --no-experimental-require-module.
• Executing the TS file directly with node index.ts (using the aforementioned on-by-default type stripping)

Bugs are expected to be fixed by those affected by it

• I'm interested in working on this issue

Compensating engineering work will speed up resolution and support the project

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