Context Engineering: How to Manage Context for AI Models and Agents

Claude's context window holds 200,000 tokens. Gemini's stretches to two million. But response quality starts degrading long before the window fills up. Window size doesn't solve the context problem — it masks it. Prompt engineering teaches you how to ask . Context engineering teaches you what to feed the model before asking. And the second one shapes the answer more than the first. Andrej Karpathy put it this way : "Context engineering — the delicate art and science of filling the context window with just the right information for the next step." Tobi Lütke, CEO of Shopify, popularized the term itself, and Gartner declared in July 2025: "Context engineering is in, and prompt engineering is out." This piece covers concrete techniques, models, and patterns. Things that actually work when you're using AI agents in development every day. Prompt vs Context: Where the Line Falls Here's an analogy that works: you're hiring an expert consultant. Prompt — your question: "What should I do?" Cont