ableton-template.mjs builds the stripped Set (1 audio track + Main, no MIDI, no returns) and installs it to each Mac's User Library/Templates, so Live's browser lists it under Templates > AC Blank. Verified on neo and blueberry. What it is NOT: the Set that ⌘N opens. That is still Ableton's stock 2-MIDI/2-audio/2-return default, and three plausible mechanisms were ruled out across full Live restarts rather than assumed: - BaseFiles/ is not the default-set source. It is only where Live copies a Set opened from outside the User Library, as a working copy. - "Save Live Set As Default Set..." behaves like a template save — it writes to User Library/Templates and ⌘N is unchanged afterwards. - No default/template/.als pointer is written to Preferences.cfg. Recorded in TEMPLATE.md so nobody re-walks them. Next lead is watching Live's file I/O during ⌘N to see what it actually reads. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>