Tell an assistant something early in a long chat, then ask about it thirty turns later.
Most chat assistants remember by keeping the last few messages and forgetting everything before that. It works until the conversation gets long, and then something you said near the start is simply gone, with nothing in any log to say it was ever there.
Type a fact, a vertical bar, then a question. The fact is dropped into the second turn of a thirty-two turn support conversation, buried under thirty more turns, and your question is asked at the very end. You can also type a question on its own and ask it against the conversation as written.
The page shows three kinds of memory filling up: the recent messages held word for word, older stretches squeezed into short summaries, and single facts pulled out and stored on their own. It shows what got thrown away to stay inside a fixed budget, and it answers your question twice, once with memory and once with only the recent messages, so you can see which one still knows.