Lesson learned
Retros that change what happens next
A "Lesson learned" captures a single insight surfaced during a retrospective or post-mortem, paired with a concrete preventive action so the same problem is less likely to recur. Unlike a general action item or task, it always ties the fix back to a specific root cause and the incident or discussion that revealed it. It differs from a decision record in that it documents what went wrong and how to avoid it, rather than a choice made going forward.