Shipped in 8.5. Until now, free-tier users with more than one vial could indefinitely rotate which vial was "active" by tapping any locked card and choosing Make this my active vial — effectively bypassing the single-vial Pro gate forever.
v8.5 closes the loophole. Locked vials and locked supplements now route directly to the upgrade screen. No more switch affordance, no more escape hatch. Existing free-tier users keep their original active vial untouched; the only way to use a different one is to upgrade.