Frozen Cost Baseline Catches AI Agent Spend Creep That Rolling Dashboards Miss

AI agent deployments can silently accumulate higher costs through gradual growth in input context — system prompts, tool schemas, and server configurations — at rates as low as 0.35% per day. Standard fleet dashboards rely on rolling baselines that adapt alongside the creep, meaning the two figures never diverge enough to trigger an alert. A developer tested this across six simulated 60-day scenarios and found that four rolling detectors raised zero alarms even as costs climbed 22.6% overall. By contrast, a frozen 'anchor' baseline pinned to day zero flagged the same drift by day 9, with no false positives on stable fleets. The author recommends running both approaches in parallel, noting that rolling detectors remain useful when workload volume spikes while the context floor stays flat.