That's stronger than the current 1st level version once your Proficiency bonus is +5.
I'd just make it a flat +2 bonus.
Sure, but so are offensive cantrips at that point too (or even earlier in vanilla).
Sure, but so are offensive cantrips at that point too (or even earlier in vanilla).
No better than proficiency with shields. Worse, in fact, since shields give you +2 AC without costing your reaction.I would re-work it into something that affects a single enemies attack roll, instead of a +ac until next round. Being able to shield up when you are surrounded by enemies, even at a lower value, as a cantrip seems way to good to me.
Until the start of your next turn, you have a bonus to AC equal to your proficiency modifier. This includes the triggering attack. You also take no damage from Magic Missile.
Personally, I wouldn't do this both for the reason @Satyrn mentions (multi-class / Magic Initiate feat abuse) and because your proposed reaction shield cantrip is better than the Defensive Fighting Style. And I don't see making mages better at defense all-day-long than warriors as a desirable change in D&D.
Aye. That's another consideration that'd stop me implementing the OP's version.
I could contemplate using a version of it thattgranted an AC calculation of 10 + Proficiency Bonus + Dex modifier, though.