I have lost the same afternoon three times, in three different ways.
The first time, I spent hours with a chatbot thinking through my server setup — which drives, which filesystem, what to do about backups. We weighed options. I discarded two of them for good reasons. Weeks later I sat down to actually build the thing, went looking for that conversation, and it was gone. Not deleted, just unfindable, which amounts to the same. I started over and made roughly the same decisions, minus the reasoning.
The second time, I switched assistants. The new one was better at the task and knew nothing about me. Not my machines, not my naming conventions, not why the media server lives where it lives. Everything I had explained once, I explained again. That is a strange feeling: you have a competent helper who is also, permanently, on their first day.
The third time was the worst, because there was nobody to blame. I opened a config file I had written myself and could not reconstruct why it was that way. There was clearly a reason — it was too specific to be an accident. The reason had been in a conversation, and the conversation was gone.
Three losses, one shape. In each case the work survived and the thinking behind it did not.
That is when the rule showed up, and it is boring enough to fit in one line: knowledge goes in files, not in chat.
A chat is a conversation. Conversations are supposed to be ephemeral — that is not a bug, it is what conversations are. The mistake was mine: I used a medium designed to be forgotten as a place to store things I wanted to keep.
What this looks like in practice is unglamorous. There is a folder of plain text. Each project has a file that says what it is and what state it is in. Decisions get their own file, and every entry answers why, because the what is usually obvious from the thing itself six months later, and the why never is. When I start working with any assistant, the first thing it does is read those files.
The test is simple: I can swap the assistant and lose nothing. That happened again recently, and it was uneventful. Uneventful is the entire point.
I would like to end there, but it would be too tidy.
Writing things down is work, and it is work at exactly the moment you least want to do it — you are finished, it works, you want to stop. The discipline only pays later, to a version of you who is not in the room yet. I still lose things. Usually it is the small stuff: a decision that seemed too obvious to record, and turns out six months on to have been the entire load-bearing choice.
But the shape of the loss has changed. It used to be everything since the last time, now it is a line I forgot to write. A trade I will take any day.