In Windows the default total path length must not exceed 260 characters (
255 characters of filename +
null terminator + probably for final
\ in case the path is a directory or simply for even rounding). It was a relic from DOS's 8.3-name era where a 260-character path is a really deep path.
It's possible that your path to the folder was already very long, so the remaining part for your filename is just 129. If you want longer path, you have several solutions:
Since Windows 10 there's another option by removing MAX_PATH limitation§. You can enable it by setting
HKLM\SYSTEM\CurrentControlSet\Control\FileSystem LongPathsEnabled in registry or set Computer Configuration > Administrative Templates > System > Filesystem > Enable NTFS long paths in group policy
‡The maximum path of 32,767 characters is approximate, because the
\\?\ prefix may be expanded to a longer string by the system at run time, and this expansion applies to the total length.
§Starting in Windows 10, version 1607,
MAX_PATH limitations have been removed from common Win32 file and directory functions. However, you must opt-in to the new behavior.