NSTextStorage: textView.string = / replaceCharacters(full range) reports the whole text as editedRange, so offset-tracked line markers collapse

If you keep per-line markers (breakpoints, bookmarks) as UTF-16 offsets and move them in NSTextStorage.didProcessEditingNotification with editedRange + changeInLength, a whole-buffer replace breaks them. Setting NSTextView.string (a reload from disk) and storage.replaceCharacters(in: NSRange(0, length), with:) (format document, which undo replays too) both report editedRange = the whole new text. Every offset inside the old text maps to the edit start (0), so all markers merge onto line 1. If your code dedupes markers that meet, they are deleted for good. Fix: when the edited range spans a marker line, re-locate it by its saved line text (nearest match, skipping lines already taken), or narrow the edit to the real change with a common-prefix/suffix diff of the old and new strings (keep the old string, or take it in willProcessEditing). Also don’t place markers by text while the storage is still empty (async file load), or they all look lost.