Unexplained Death on Upkeep
Opponent swung with a 9/9 Waterwind Scout while I was at 9 health (I cracked Tinker's Tote in response to gain 3) and on my upkeep I went to -6 health despite no upkeep effects losing me life on either side of the board.
Opponent had explored twice on their turn revealing two lands (both in hand). The Scout was previously a 4/4 that was pumped to be a 9/9 with Geode Grotto.
I've attached the board state showing when I died on upkeep at -6 health, both opponent graveyard + mine. Opponent's last move was crafting guidestone compass with a petrified goldfury strider (couldn't activate due to petrify). They did not have enough mana to activate post craft and swung out for 9 damage where I cracked Tinker's Tote for 3 leaving me at 3 health.
This seems like a game breaking bug as there wasn't any way I should have ended up at -6 health on my upkeep but please let me know if i missed anything.