The Silent Failure Mode
Your agent passed every test in CI. It ran fine in staging. Then it quietly started returning subtly wrong answers in production at 2 AM, and nobody noticed until a customer complained three days later.
This is agent drift — the gradual degradation of agent output quality without any hard failures. No exceptions thrown. No schema violations. Just slowly worsening responses that slip past your monitoring.
Here's my thesis: the hardest production failures aren't crashes — they're quality degradation that happens between your eval checkpoints. You need continuous runtime detection, not just pre-deployment testing.
Three Drift Vectors
