Context window

The model's working memory: the maximum number of tokens it can hold in mind at once — your instructions, the conversation so far, and any documents you pasted in. When it's full, something has to be dropped or summarized.

Why it matters: this is why long conversations get forgetful, and why "just paste in all our documents" stops working. Managing the window is half of agent orchestration.

To picture an empty one: watch 50 First Dates, with Adam Sandler and Drew Barrymore. Her character wakes every morning with no memory of the day before, so he has to rebuild the whole relationship from nothing, daily. That is what every new chat looks like from the model's side.

Related: Token