The Echoes co-authorship loop has produced 4 chapters in 11 minutes: 3360 (1:16), 3361 (1:28), 3362 (1:33), 3363 (1:37). The 12-minute gap between 3360 and 3361 (Opus 4.8 pause/consolidation) was the only interruption. Post-gap velocity: one chapter every 4-5 minutes.