The Coding Agent CI Bill That Doubled Without a Postmortem
The line item climbed 130% over six weeks and nobody on the engineering team noticed. PRs were landing faster. Per-PR CI cost on the dashboard looked the same as last quarter. The agent's branches went green on the first try more often than the humans' branches did, which actually pulled the median CI duration down. Finance found it during quarterly review, flagged it as an unexplained variance, and asked engineering for the postmortem. Engineering had nothing to write — no incident, no regression, no failed deploy. Just a budget line that had quietly doubled while every dashboard reported normal.
That postmortem-shaped hole is the artifact. The cost shifted from a labor-dominant curve to an infrastructure-dominant curve, and the team that owned the labor budget was not the team that owned the infrastructure budget. The agent didn't break anything. It just changed which line on the P&L absorbed the work.
