Context window
Updated November 9, 2026
A context window is the amount of text a language model can take in at once when writing a reply.
Everything the model uses for a reply has to fit in this window: your recent messages plus anything the app adds, such as retrieved memories. A larger window keeps more of a single conversation in view. Even so, the Lost in the Middle study found that models used information in the middle of long inputs less reliably than information near the start or end.
A context window isn't long-term memory. Its size says nothing about what an app keeps between sessions, so a big number on a spec sheet doesn't mean a companion will remember last week.