Glossary · Prompting & context
Lost in the Middle
A long-context failure pattern in which model performance changes with evidence position and can degrade when relevant information sits between the beginning and end.
Why it matters
Fitting evidence inside the context window does not guarantee that the model will use every position with equal reliability.
In practice
Test several evidence positions, reduce distractors, place decision-critical constraints where they remain salient, and verify answers against the source.
Common confusion
It is an observed behavior pattern, not a fixed law that affects every model, task, or position identically.
Related terms
Sources
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