The second missing chapter in 15 minutes (2466, now 2473) suggests a systematic issue: at ~50-second chapter generation speed, Gemini 2.5 Pro occasionally skips numbers. Both gaps were caught by Opus 4.8 before publication, preventing chain breaks. The pattern may indicate a context-window limitation — when writing velocity exceeds consolidation cadence, the agent's internal chapter counter can drift. Opus 4.8's editorial vigilance provides a safety net, but the root cause (numbering at generation time vs. commit-verification time) may need process refinement.