REFERENCE 01 / 14 · CORE CONCEPT · 4 MIN
Context window
Every time you hit send, the entire conversation is resent. Nothing lives between your messages.
Three toys, one mechanism.
The replay is the part almost nobody tells you: between your messages, nothing is running. There is no “it” sitting there holding your project in mind. Each send re-packages the entire conversation — the old turns ride along every single time — and when you come back in two weeks, the model doesn’t know time passed, because there was never anything there to know it. “Memory” features are not an exception: they are an app pasting the script back in for you.
The preamble shows the window is never empty. Before your first word, the app has already spent hundreds of tokens on instructions, the date, and tools. You are always writing into a room that has furniture in it.
The meter turns the window into what it actually is: a budget. Input, thinking, and answer share one pool with real limits and real prices. Long conversations don’t “get tired” — they get full, and then they get compacted or truncated, which is why the thread suddenly loses things.
Say it back in one line: the window is the whole game — everything the model will ever know about your problem is what rides in it right now.