Context engineering for production AI agents
Prompt engineering is the discipline of writing the right words for a single turn. Context engineering is the discipline of curating everything that ends up in the model's context window across an entire agent run — system prompt, tool definitions, retrieved documents, conversation history, scratchpad notes, sub-agent outputs. Anthropic named this discipline in September 20251 because production agents kept hitting the same wall: the model was smart enough, but the context it saw was wrong.
This post covers what context engineering is, the four strategies you actually use, the failure modes that show up in production, and the tooling that does each one well.