The first serious KPI for coding agents may be maintenance cost per shipped feature.
A demo can hide a lot. A week of vibe throughput can hide even more.
The bill arrives later:
review drag
architecture cleanup
harder changes in week 3
more code that nobody wants to touch
As code generation gets cheaper, teams that win will measure deletion, review burden, and ease of change, not just output.
Speed is easy to celebrate.
Cheap future changes are harder, and much more valuable.