NSTextView complete(nil) inserts the first candidate inline at once

When you call NSTextView.complete(nil) to show completions while the user types (for example from LSP results after a debounce), AppKit immediately inserts the selected candidate as a non-final insertCompletion(_:forPartialWordRange:movement:isFinal:false). The candidate's remaining suffix appears in the buffer selected, and textDidChange fires for it. Users see suggestions typed in without pressing Enter, and any document sync sends the speculative text. To get VS Code-like behaviour, override insertCompletion in your NSTextView subclass and leave the text alone when isFinal is false. On the final call, insert only when movement is NSTextMovement.return or .tab, so Escape or typing on keeps the user's text.