Bedbugs/history
The infestation started in the middle bedroom upstairs, some time in mid-2019. The occupant of that room had been experiencing mysterious skin irritation and itchyness for some weeks before identifying the problem as bedbug bites, at which point the rest of the household was immediately informed. The occupant immediately threw out or bagged many items from their room.
Not long after that, Harena and I found evidence of infestation in our mattress (in the left bedroom) -- which we immediately quarantined in a disused car, and swapped in a spare (and very uncomfortable) mattress for several months.
We have several times since found isolated bedbugs in the left bedroom, and one time an apparent cluster of recently-hatched bugs, but no ongoing infestation. The bedroom on the right did not seem to be a problem for some reason.
We did two bombing runs over the next 9 months or so -- each one being a short-term success but not getting rid of the problem.
The whole-house heat-treatment which is apparently the gold standard for eliminating bedbug infestations did not seem to be an option, both because of the expense and because of the sheer quantity of meltable things that would need to be removed from the house.
I came up with a plan for fighting the problem in the middle bedroom the morning of May 27, 2020. That same morning, we became aware that the problem had escalated to the right bedroom. I posted the plan in our household Discord on 5/29.