Silent regressionnobody noticed for 9 days
Token burnretry loop, 40x the cost
Upstream schema changetool calls quietly failing
Model swap driftnew model, new failure modes
Hallucinated answersent to a real customer
Manual patchno test, broke two other flows
Stale promptrules changed, prompt did not
Forgotten edge casefixed once, regressed again
Debugging by vibesno evals, no ground truth
3am pagethe agent, again
55%
of runs passing evals, climbing version over version. That is the loop compounding: every failure becomes a fix, every fix is proven, and your agents get more accurate, cheaper, and more reliable over time.