Context rot
When accumulated context makes the model's job harder instead of easier.
Context rot happens when a prompt accumulates stale, irrelevant, or conflicting material until the model has a harder job.
What it means
Context rot appears when old instructions, irrelevant snippets, stale state, duplicate documents, or contradictory notes stay in the prompt long after they stopped helping.
Why product teams care
The user sees worse answers, missed instructions, higher costs, and slower responses even though the system is technically sending more information.
Understudy angle
Understudy can compare trimmed context, reordered context, and retrieval filters against the same eval to find what actually helps.
Context quality matters more than context volume.
Audit one long prompt and delete everything that does not affect the rubric.