context-engineering-fundamentals

# Context engineering fundamentals Context engineering is the practice of managing an LLM's limited attention budget. Use this skill to keep instructions, evidence, and state available during long work. ## Core concept **Context windows are constrained by attention mechanics, not only token capacity.** A large context limit does not guarantee equal use of every item. ## The lost-in-middle effect The "Lost in the Middle" experiments show that retrieval quality can change with information position. The result depends on the model, task, context length, and number of documents. | Position | Common test result | |----------|--------------------| | Beginning | Often easier to retrieve | | Middle | Can be harder to retrieve | | End | Often benefits from recency | **Implication:** Keep critical constraints easy to find and repeat them near the decision that uses them. Do not assume position alone predicts recall. ## Context degradation patterns ### 1. Lost-in-middle Information in the middle of long context gets lower attention weight. **Mitigation:** Structure with explicit sections. Put critical constraints at start AND end. ### 2. Context poisoning Errors compound when incorrect information enters context (from tool outputs, summaries, or earlier mistakes). **Mitigation:** Validate intermediate outputs. Don't blindly trust previous responses. ### 3. Context distraction Irrelevant information forces attention allocation away from relevant content. Models can't "skip" ...