Memory
The temptation with an agent is obvious: have it write down everything it does, just in case. At first it works. The problem does not arrive with volume — it arrives the day everything weighs the same.
The higher it goes, the less fits and the longer it lasts
Four questions
Keeping it all in one place and searching by similarity breaks quickly: March's log ends up burying the rule that still holds. Each memory exists because it answers something the others do not.
What the agent believes today about the thing it handles: how it is going, which theories are open, what it left half done. Read when opening, updated when closing. It is the only memory deliberately overwritten. A three-month-old state is not history: it is noise shaped like a fact.
What was done, what was decided and why. Detailed and chronological: it only makes sense inside its context, and inside it there is nothing better.
Little, and hard to earn. A lesson does not get in because someone writes it down with conviction: it gets in once different agents have used it on different projects over time.
What is no longer up for debate because a human signed it. It does not compete with the rest: it wins. Without this layer, every agent re-argues the same thing every week.
Rising
Someone solves something and writes it in the project log. It stays there for as long as it only helps there.
Another agent, on another project, runs into the same thing and applies it. One coincidence is not a pattern; two start to be.
Once it has proved useful more than once and in more than one place, it rises to shared memory. Not before: a shared memory full of special cases stops being shared.
Why this way
When each question has its place, the answer arrives whole. Without a hierarchy, searching returns thirty similar things and none that settles anything.
Today's state gets overwritten; the log does not. Mixing them forces you to read dates to know what is still true.
In the brain, not everything you live reaches the cortex: what repeats does. That culling is not a flaw in the system, it is what keeps remembering useful.
It does not repeat the mistake another one made six months ago on a project it never heard of. That is the whole value of memory that crosses.