Summary

Filed as oven-sh/bun#45059 on 2026-10-12.

• On Windows, fs.mkdirSync(p, { recursive: true }) throws ENOENT with an empty path for p = ./, .\ or sub/... All three name the current directory, which exists. fs.promises.mkdir and callback fs.mkdir fail the same way
• Node.js v26.11.1 and Deno 2.9.7 return without an error
• The open fix PRs #42014 and #42635 do not fix it. #40536 does. #45410, opened on 2026-10-16 with Fixes #45059, does too (it does not touch the ..-prefixed EEXIST cases)
• Cause: os_path_kernel32 normalizes these paths into an empty string, and only the exact input "." is special-cased (Evidence: source)
• A possible fix: if the normalized result is empty, use "." (move the "." special case after the normalization)

Repro script: research/repro-enoent.cjs. The same cases are in tests/mkdir-recursive.test.ts. The full write-up of the related EEXIST bug is in the results.

Evidence: runs

Environment and builds

Windows 11 Home 10.0.26300 x64. The PR builds are bun-windows-x64.zip from each PR's Buildkite CI; each SHA-256 matched the value listed by Buildkite.

Results

The same result for mkdirSync, fs.promises.mkdir and callback fs.mkdir.

Output of repro-enoent.cjs (verbatim)

Bun 1.4.3:

NG . EEXIST EEXIST: file already exists, mkdir '.'
NG ./ ENOENT ENOENT: no such file or directory, mkdir
NG .\ ENOENT ENOENT: no such file or directory, mkdir
NG sub/.. ENOENT ENOENT: no such file or directory, mkdir
OK sub/.
NG promises . EEXIST
NG callback . EEXIST
NG promises ./ ENOENT
NG callback ./ ENOENT
NG promises .\ ENOENT
NG callback .\ ENOENT
NG promises sub/.. ENOENT
NG callback sub/.. ENOENT
OK promises sub/.
OK callback sub/.

PR #42014 and PR #42635 (identical output):

OK .
NG ./ ENOENT ENOENT: no such file or directory, mkdir
NG .\ ENOENT ENOENT: no such file or directory, mkdir
NG sub/.. ENOENT ENOENT: no such file or directory, mkdir
OK sub/.
OK promises .
OK callback .
NG promises ./ ENOENT
NG callback ./ ENOENT
NG promises .\ ENOENT
NG callback .\ ENOENT
NG promises sub/.. ENOENT
NG callback sub/.. ENOENT
OK promises sub/.
OK callback sub/.

PR #40536, PR #45410, Node.js and Deno (identical output):

OK .
OK ./
OK .\
OK sub/..
OK sub/.
OK promises .
OK callback .
OK promises ./
OK callback ./
OK promises .\
OK callback .\
OK promises sub/..
OK callback sub/..
OK promises sub/.
OK callback sub/.

Evidence: source

Where the path becomes empty

src/runtime/node/types.rs L1072-L1088 (Bun 1.4.3, c6da4a4d3), in os_path_kernel32 for a relative path:

            // Handle "." specially since normalizeStringBuf strips it to an empty string
            if s.len() == 1 && s[0] == b'.' {
                // SAFETY: see alignment note above (PathBuffer reinterpreted as [u16]).
                let buf_u16 = unsafe { bun_core::bytes_as_slice_mut::<u16>(&mut buf[..]) };
                return Ok(strings::to_kernel32_path(buf_u16, b"."));
            }
            let normal = bun_paths::resolve_path::normalize_string_buf::<
                true,
                bun_paths::platform::Windows,
                false,
            >(s, &mut b[..]);
            if !strings::fits_in_wide_path_buffer(normal) {
                return Err(NameTooLong);
            }
            // SAFETY: see alignment note above (PathBuffer reinterpreted as [u16]).
            let buf_u16 = unsafe { bun_core::bytes_as_slice_mut::<u16>(&mut buf[..]) };
            return Ok(strings::to_kernel32_path(buf_u16, normal));

• The comment says normalize_string_buf strips "." to an empty string, so "." is handled before it
• ./, .\ and sub/.. normalize to the same empty string, but the check only matches the one-character input ".". They reach mkdir as an empty path, which matches the empty path in the ENOENT message

Why each PR fixes it or not

#42635's description also notes that child\.. still reports ENOENT with that PR and says #40536 covers it. #40536 is based on 1.4.1 and has not been updated since 2026-08-26.