I was able to experience this extensively firsthand as a non-host today.

Most of the time, the fog would be updated at the start/end of the next boardpiece's turn, but sometimes it would take a few boardpiece's turns.

There is a game message SerializableEventUpdateFog (and sometimes SerializableEventUpdateFogAndSpawn) that gets sent out to all players on occasion, including after a player moves. I wonder if that message is somehow being stopped from being sent by a silent error in HR somewhere.

A stopgap could be to manually send out SerializableEventUpdateFog when appropriate, but that wouldn't be a true fix. We could have both host and client log when SerializableEventUpdateFog message are sent out and received, to start tracking down if indeed messages are getting lost somewhere.

I tried adding SerializableEventUpdateFog to Boardsyncer for testing, but there was no apparent change. Clients would frequently still say that after another player moved into an unexplored area it would remain blank to them until an action was used.

I tried adding SerializableEventUpdateFog to Boardsyncer for testing, but there was no apparent change. Clients would frequently still say that after another player moved into an unexplored area it would remain blank to them until an action was used.

Thanks - one possibility down. Closer to inevitably getting to the bottom of it. To get us closer to figuring out the cause:

We can whip up a small mod (or just dev HR build) that both a host/client can run. We'd over overwite the random seed to make experiments consistent. We'd write out details about every message sent between host/client and figure out (hopefully) finally figure out what delta is being caused when HouseRules is enabled.

I believe this is not fixed!