Summary
On the opponent's turn, I resolved their landfall triggers. The client then auto-passed priority on a sorcery they cast afterwards in the same turn.
I had untapped mana and two castable counterspells.
I made no input when the spell was cast.
It happened twice in one match, on turns 5 and 7.

Steps to reproduce

Hold a counterspell with enough untapped mana on the opponent's turn.
The opponent plays a land that puts landfall triggers on the stack. I resolve them.
Later in the same turn, the opponent casts a spell.
Priority comes to me with the counterspell listed as castable.

Expected result
The game stops and waits for my response to the opponent's spell.

Actual result
The client sends a pass by itself about 2 to 3 seconds after receiving priority, and the spell resolves.

Evidence from Player.log (times AEDT, UTC+11)

Match ID: 7eac94d5-dd10-422e-b71e-6a16fec7d4ed, Play queue, 23 Oct 2026. Player: auscontra.
Turn 7, 8:50:43 pm: the client sends SetSettingsReq with stackAutoPassOption: AutoPassOptionResolveAll, turnNumber: 7, together with a pass at gameStateId 143. This is my response to the landfall triggers.
Turn 7, 8:50:47 pm: the opponent casts Circuitous Route. ActionsAvailableReq at gameStateId 150 lists Spell Pierce and Quandrix Charm as castable.
Turn 7, 8:50:49 pm: the client sends PerformActionResp ActionTypePass for gameStateId 150. I made no click or key press, and the only UI message in between is a card hover.
Turn 5, same pattern: at 8:49:57 pm the client sends the same ResolveAll setting with turnNumber: 5. The opponent casts Mossborn Hydra at 8:50:00 pm, and the client passes at 8:50:03 pm with castable responses available.
Result: both spells resolved, and I lost on turn 7.

Environment

Windows PC
Client version as logged: 2026.64.50.14589
Default auto-pass setting: AutoPassOption_ResolveMyStackEffects