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n. / Quality and evaluation
Prompt regression
Definition
A prompt regression is a drop in quality caused by changing a prompt: something that used to work now fails, even if the new wording looks better.
In more detail
Prompts are fragile because small edits shift behavior in unrelated cases. The defense is a saved set of cases that you run before and after every edit, with the prompt version recorded on each run. When a score falls, the version history shows what changed.
Example
A prompt edit adds a polite tone. Replies get friendlier, but refund requests that mention a date now fail because the new wording shifted the model's focus.
