Keep adding text below until the bar turns red.

Working memory (8k tokens)5% full
hidden instructionsyouthe AIa file
  1. The app's hidden instructions~400 tok
  2. A 40-page PDF you uploadedfell out

1 earlier turn has fallen out. The AI can no longer see them — that's the whole reason it "forgot". A bigger window delays this; it never removes it.

Token counts are estimates (~4 characters per token); real tokenizers differ by model.

That bar is the model's context window: everything it can see at once. When it's full, something has to give.

Anthropic's definition: the context window is "all the text a language model can reference when generating a response, including the response itself." They call it a "working memory".

It isn't what the model learned in training. It's the desk in front of it right now, and it's measured in tokens.

What fills the window on a typical request

Hidden instructions from the app

Takes space?
Yes

The whole conversation so far

Takes space?
Yes

Files and pasted code

Takes space?
Yes

The answer being written

Takes space?
Yes, included

How big? It depends on the model. Anthropic's docs describe windows of "up to 1M tokens, depending on the model."

Bigger isn't automatically better. Anthropic: "As token count grows, accuracy and recall degrade, a phenomenon known as context rot."

Try it with the rules off. In the sandbox, fill the window to the brim, then ask a question about the very first paragraph. Then remove half the text and ask again.

Check yourself

0/3 got it

Saved on this device only. No account, no streaks.

Next in how the AI thinks: Why the AI "forgot".