AI glossary
Context window
A context window is how much an AI model can hold on its desk at once: your messages, the conversation so far, instructions, files and anything a tool fetched, measured in tokens. It’s large in most tools as of 2026, but answers can get worse as it fills, and some tools quietly summarise older parts to make room.
Think of it as
The size of the desk.
Why it matters at work
When a long chat starts going wrong, a new chat started from a short summary often works better than arguing with it. Module 5 teaches this, and how to keep files that outlive any chat.
Sources
- Context Rot: How Increasing Input Tokens Impacts LLM Performance (vendor research: Chroma sells retrieval software) (opens in a new tab) Chroma (Hong, Troynikov and Huber), 14 July 2025.