I was playing vs the AI (game: #90190242). We had a Mountebank and Soothsayer plus a Lighthouse and Inheritance. I Inherited the Lighthouse, so I had one face up on most turns. The AI used Mountebank and the Lighthouse did not ever block the attack.
What am I missing here, or is this a bug?
I am not sure of the answer. Is it possible that Inheritance (and, therefore, your estate/Lighthouses) takes effect only on your turns? And you are looking for an effect that comes into play only when it's your opponent's/opponents' turn(s).
If so, it would mean that you played your Estate/Lighthouse on your turn. But, when your turn finished, your played, face-up, "Lighthouse" suddenly lost it's defensive ability (ie, it became an oddly-placed, face-up, Estate). If my guess is correct; it seems a bit unfair. But Dominion has many of these quirks--where the actual gameplay is a little counter-intuitive.
I'll be interested to hear from more experienced players...cuz it's possible that my guess is wildly wrong. :-)
The "protect me from an attack" part of Lighthouse will not work when you have it inherited.
Lighthouse reads, in part (under the dividing line):
While you have this in play, when another player plays an Attack card, it doesn't affect you.
Notice the bold part, it only works when it is in play. If you have inherited Lighthouse and play an Estate, you have the Estate in play, not the Lighthouse. Due to the Fall 2019 errata, the Estate no longer takes on the abilities of the Lighthouse (as it used to do before), but "only" becomes an Action card that plays the set aside Lighthouse (the relevant part of Inheritance reads)
During your turns, Estates are also Actions with "Play the card with your Estate token, leaving it there."
So again, the (new since 2019) situation is that you have an Estate in play and a Lighthouse set aside, so Lighthouse does not protect you from your opponent's attacks, because its condition is not met :(
So my point here then is there is a bug. While I can understand the inherited estates not protecting me, the actual lighthouses I did have also did not protect. I am assuming the game code treated all instances of lighthouse as inherited.
Definitely not working as intended. The original lighthouse cards in my deck should work as intended regardless of the inherit (which should only apply a change to Estates....not change the original card).
When I answered yesterday, I didn't look at the actual game, as the reason for the behaviour seemed clear in the Inheritance/Lighthouse interaction. I now looked at the game and what happened, the answer is still the same: No bug.
I went through the log 4 times, looking for mentioning of "Lighthouse", "Mountebank", "Soothsayer" (the 2 attacks in the kingdom) and "Black Market" (a potential source for other attack cards).
1) Whenever "Lighthouse" was mentioned. If you played a "real" one (not the inherited one), I looked what Lord Rat did their next turn. They never attacked, mostly playing their Jack of All Trades.
2) Whenever "Mountebank" was mentioned. If it was played by Lord Rat, I looked at what you did your previous turn. You had played an inherited Estate in some of them, but never a "real" one from your hand.
3) Whenver "Soothsayer" was mentioned. Only you gained one, so Lord Rat never played one.
4) Whenver "Black Market" was mentioned. You had one and bought a Steward and Sir Martin with it. Sir Martin never was played, neither by you nor Laord Rat.
So I'm still standing by my previous analysis. You unfortunately never had a Lighthouse in play when Lord Rat attacked you, so you were not proteced.