git annex add is not fully compatible with multibyte-characters in filenames and may generate filenames with invalid character sequences.
### What steps will reproduce the problem?
+```
$ git init test; cd test
$ git annex init test
$ echo bla > 01-06\ 三石琴乃・富沢美智恵・久川綾・篠原恵美・深見梨加\ -\ Tuxedo\ Mirage.flac
$ git annex add 01*
-
+```
The last command generates an invalid character sequence as filename which, depending on the filesystem, may cause an error:
Example output:
+
+```
add "01-06 \344\270\211\347\237\263\347\220\264\344\271\203\343\203\273\345\257\214\346\262\242\347\276\216\346\231\272\346\201\265\343\203\273\344\271\205\345\267\235\347\266\276\343\203\273\347\257\240\345\216\237\346\201\265\347\276\216\343\203\273\346\267\261\350\246\213\346\242\250\345\212\240 - Tuxedo Mirage.flac"
.git/annex/othertmp/: openTempFile template ingest-01-06 三石琴乃・富沢美智恵・久川綾・篠原恵美・深見梨�: invalid argument (Invalid or incomplete multibyte or wide character)
failed
add: 1 failed
-
+```
### What version of git-annex are you using? On what operating system?
git annex 10.20250630