Definition
Plain language
The tendency of language models to overlook information buried in the middle of a long input while paying attention to the start and end.
As stated in the literature
A documented long-context degradation pattern where retrieval and use of facts placed mid-context is weaker than at the boundaries; raised and then ruled out as the cause of constraint decay in compaction studies.
Why it matters: It warns that feeding a model more context doesn't guarantee it uses all of it, which can quietly cause it to miss key information.
For example, given a long document, a model might correctly use a fact from the first or last page but overlook an equally important fact tucked into the middle.
Heard on the show
“There's the "lost in the middle" result, there's "context rot.”Episode 164 — The Summarizer That Quietly Deletes Your Agent's Safety Rules