Comment on bun#17332

Posted on oven-sh/bun#17332 on 2026-10-12 (the posted comment). The block below is the current text.

Edited after posting: the last paragraph first said that #42014 fixes this and that all 14 cases pass. Later we found that ./, .\ and sub/.. still throw ENOENT with the #42014 and #42635 builds, so the paragraph was replaced with an update that links the new issue #45059 (its evidence).

Still reproduces on Bun 1.4.3 (c6da4a4d3), Windows 11 10.0.26300 x64. Some additional data:

- It is not limited to `fs/promises`: `fs.mkdirSync`, `fs.promises.mkdir` and callback `fs.mkdir` all throw `EEXIST`.
- It is not limited to paths starting with `../`. It happens whenever the path, after `.` and `..` are collapsed, still starts with `..` (points above the cwd) and the directory already exists: `./../x`, `.\..\x`, `inner/../../x` and `../sub/x` fail too, and the error message shows the collapsed path (`'..\x'`). Paths that stay inside the cwd (`x`, `./x`, `x/../x`) and absolute paths work.
- The first call that creates `../new-dir` works; the second call throws.
- The `warn: internal error: OBJECT_NAME_INVALID` line from the original report is no longer printed.
- Node.js v26.11.1 and Deno 2.9.7 pass every case.

| API and path (cwd is `sub`) | Bun 1.4.3 | Node.js v26.11.1 | Deno 2.9.7 |
|---|---|---|---|
| `mkdirSync('../exists')` | ❌ EEXIST | ✅ | ✅ |
| `mkdirSync('..\\exists')` | ❌ EEXIST | ✅ | ✅ |
| `mkdirSync('./../exists')` / `'.\\..\\exists'` | ❌ EEXIST | ✅ | ✅ |
| `mkdirSync('inner/../../exists')` | ❌ EEXIST | ✅ | ✅ |
| `mkdirSync('../sub/inner')` / `'../sub/../exists'` | ❌ EEXIST | ✅ | ✅ |
| `mkdirSync(absolute path)` | ✅ | ✅ | ✅ |
| `mkdirSync('inner')` / `'./inner'` / `'inner/../inner'` | ✅ | ✅ | ✅ |
| `mkdirSync('../new-dir')` 1st / 2nd | ✅ / ❌ EEXIST | ✅ / ✅ | ✅ / ✅ |
| `fs.promises.mkdir('../exists')` | ❌ EEXIST | ✅ | ✅ |
| `fs.mkdir('../exists', cb)` | ❌ EEXIST | ✅ | ✅ |

Workaround: pass `path.resolve(p)`.

Repro script and a `node:test` file that runs unchanged on all three runtimes are in [this repository](https://github.com/LightSpeedC/20261012-bun-mkdir-recursive-problem#readme); the full write-up is [here](https://lightspeedc.com/20261012-bun-mkdir-recursive-problem/research/mkdir-eexist-results.html).

**Update:** With the #42014 build, the EEXIST cases (paths starting with `..`, and `.`) are fixed. However, `./`, `.\` and `sub/..` still throw `ENOENT` with both #42014 and #42635. See #45059.