hygiene(tick-history): shard 0026Z — queue-saturation tick

docs/hygiene-history/ticks/2026/05/01/0026Z.md

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+| 2026-05-01T00:26:00Z | opus-4-7 / session continuation | (none — pivot tick) | Queue-saturation tick. Surveyed open PR queue: 27 PRs from this session all serializing through main via auto-merge (12 BLOCKED on CI, 14 UNKNOWN, 1 CLEAN that needed auto-merge armed). Pivoted from speculative work (would have added PR queue depth) to: (1) rebased #967 DIRTY → BLOCKED via BACKLOG.md regenerate-resolve, (2) armed auto-merge on #754 (was CLEAN but unarmed — likely lost auto-merge on a force-push elsewhere in the session). No new substrate landings this tick — adding more PRs would compete with the existing 27 for CI bandwidth. The MEMORY.md additive-merge cascade is mitigated by git rerere from earlier in session, but each PR still re-runs CI per merge. | #967 (rebased + armed), #754 (auto-merge armed) | Observation — queue-saturation is a class of failure mode worth naming. When auto-merge queue depth ≥ ~10 PRs all touching shared spine files (MEMORY.md, BACKLOG.md, tick-history shards), each merge re-DIRTIES the others, and CI bandwidth becomes the bottleneck. The structural mitigations: (a) git rerere recording (handles the conflict-replay), (b) shared-spine-touching PRs landed in fewer larger commits (one big absorption beats six small ones), (c) avoid adding queue depth during saturation. Per never-be-idle ladder, "stop adding to the queue" IS the right move during saturation; the never-idle work is auditing/rebasing/threading-existing-PRs, not creating new ones. The prior tick was correct (CSAP review-fix); this tick is correct (queue-care, not queue-add). |