$ ruff --version
ruff 0.15.12

$ cat <<EOF > ./original.py
import os
from tempfile import NamedTemporaryFile

file = NamedTemporaryFile()


class TestName:
    def __init__(self, name: str):
        self.name = name
        os.chmod(name, 0o644)  # Case 1: Fix applied, correct results

    def test_name(self):
        os.chmod(self.name, 0o644)  # Case 2: Fix applied, correct results


TestName(file.name).test_name()


class TestFd:
    def __init__(self, fd: int):
        self.fd = fd
        os.chmod(fd, 0o644)  # Case 3: Fix not applied, correct results

    def test_fd(self):
        os.chmod(self.fd, 0o644)  # Case 4: Fix applied, incorrect results!


TestFd(file.fileno()).test_fd()

print("Done")
EOF

$ python3 ./original.py
Done

$ ruff --isolated --config='lint.select=["PTH101"]' check --preview --no-fix original.py
error[PTH101][*]: `os.chmod()` should be replaced by `Path.chmod()`
  --> original.py:10:9
   |
 8 |     def __init__(self, name: str):
 9 |         self.name = name
10 |         os.chmod(name, 0o644)  # Case 1: Fix applied, correct results
   |         ^^^^^^^^
11 |
12 |     def test_name(self):
   |
help: Replace with `Path(...).chmod(...)`
1  | import os
2  | from tempfile import NamedTemporaryFile
3  + import pathlib
4  |
5  | file = NamedTemporaryFile()
6  |
--------------------------------------------------------------------------------
8  | class TestName:
9  |     def __init__(self, name: str):
10 |         self.name = name
   -         os.chmod(name, 0o644)  # Case 1: Fix applied, correct results
11 +         pathlib.Path(name).chmod(0o644)  # Case 1: Fix applied, correct results
12 |
13 |     def test_name(self):
14 |         os.chmod(self.name, 0o644)  # Case 2: Fix applied, correct results

error[PTH101][*]: `os.chmod()` should be replaced by `Path.chmod()`
  --> original.py:13:9
   |
12 |     def test_name(self):
13 |         os.chmod(self.name, 0o644)  # Case 2: Fix applied, correct results
   |         ^^^^^^^^
   |
help: Replace with `Path(...).chmod(...)`
1  | import os
2  | from tempfile import NamedTemporaryFile
3  + import pathlib
4  |
5  | file = NamedTemporaryFile()
6  |
--------------------------------------------------------------------------------
11 |         os.chmod(name, 0o644)  # Case 1: Fix applied, correct results
12 |
13 |     def test_name(self):
   -         os.chmod(self.name, 0o644)  # Case 2: Fix applied, correct results
14 +         pathlib.Path(self.name).chmod(0o644)  # Case 2: Fix applied, correct results
15 |
16 |
17 | TestName(file.name).test_name()

error[PTH101][*]: `os.chmod()` should be replaced by `Path.chmod()`
  --> original.py:25:9
   |
24 |     def test_fd(self):
25 |         os.chmod(self.fd, 0o644)  # Case 4: Fix applied, incorrect results!
   |         ^^^^^^^^
   |
help: Replace with `Path(...).chmod(...)`
1  | import os
2  | from tempfile import NamedTemporaryFile
3  + import pathlib
4  |
5  | file = NamedTemporaryFile()
6  |
--------------------------------------------------------------------------------
23 |         os.chmod(fd, 0o644)  # Case 3: Fix not applied, correct results
24 |
25 |     def test_fd(self):
   -         os.chmod(self.fd, 0o644)  # Case 4: Fix applied, incorrect results!
26 +         pathlib.Path(self.fd).chmod(0o644)  # Case 4: Fix applied, incorrect results!
27 |
28 |
29 | TestFd(file.fileno()).test_fd()

Found 3 errors.
[*] 3 fixable with the `--fix` option.

$ cp ./original.py ./fixed.py

$ ruff --isolated --config='lint.select=["PTH101"]' check --preview --fix fixed.py
Found 3 errors (3 fixed, 0 remaining).

$ python3 ./fixed.py
Traceback (most recent call last):
  File "./fixed.py", line 29, in <module>
    TestFd(file.fileno()).test_fd()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "./fixed.py", line 26, in test_fd
    pathlib.Path(self.fd).chmod(0o644)  # Case 4: Fix applied, incorrect results!
    ~~~~~~~~~~~~^^^^^^^^^
  File "/usr/lib64/python3.14/pathlib/__init__.py", line 150, in __init__
    raise TypeError(
    ...<2 lines>...
        f"not {type(path).__name__!r}")
TypeError: argument should be a str or an os.PathLike object where __fspath__ returns a str, not 'int'

$ cat fixed.py
# Setup code
import os
from tempfile import NamedTemporaryFile
import pathlib

file = NamedTemporaryFile()


class TestName:
    def __init__(self, name: str):
        self.name = name
        pathlib.Path(name).chmod(0o644)  # Case 1: Fix applied, correct results

    def test_name(self):
        pathlib.Path(self.name).chmod(0o644)  # Case 2: Fix applied, correct results


TestName(file.name).test_name()


class TestFd:
    def __init__(self, fd: int):
        self.fd = fd
        os.chmod(fd, 0o644)  # Case 3: Fix not applied, correct results

    def test_fd(self):
        pathlib.Path(self.fd).chmod(0o644)  # Case 4: Fix applied, incorrect results!


TestFd(file.fileno()).test_fd()

print("Done")