shard(tick): 2026-05-16T16:44Z — cascade fully complete (8 PRs, 1h 13m); recoverable contamination Pattern 3

docs/hygiene-history/ticks/2026/05/16/1644Z.md

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+# Tick 2026-05-16T16:44Z — cascade fully complete; recoverable contamination Pattern 3
+
+## Refresh
+
+- Cron `23b8588a` armed.
+- Rate-limit: 518 GraphQL; 13 min reset → extreme cost-aware tier returned.
+- main HEAD advanced to `c96a7ed` during this tick (PR #3907 1618Z + PR #3908
+  1634Z both merged).
+- All cascade PRs now on main.
+
+## Cascade — fully complete on main (8 PRs, 1h 13m)
+
+| PR | Subject | Main commit |
+|---|---|---|
+| [#3897](https://github.com/Lucent-Financial-Group/Zeta/pull/3897) | B-0462 close-row | `4443c09` |
+| [#3898](https://github.com/Lucent-Financial-Group/Zeta/pull/3898) | 1535Z shard | `b5850f7` |
+| [#3900](https://github.com/Lucent-Financial-Group/Zeta/pull/3900) | 1547Z shard (broken paths, fixed by #3906) | (superseded) |
+| [#3903](https://github.com/Lucent-Financial-Group/Zeta/pull/3903) | 1610Z + path-depth ref table | `943cc3d` |
+| [#3906](https://github.com/Lucent-Financial-Group/Zeta/pull/3906) | fix-1547z-on-main | `ba2732a` |
+| [#3907](https://github.com/Lucent-Financial-Group/Zeta/pull/3907) | 1618Z (peer, separate scope) | `c96a7ed` |
+| [#3908](https://github.com/Lucent-Financial-Group/Zeta/pull/3908) | 1634Z cascade-complete | `bdb27a2` |
+
+## Recoverable contamination — Pattern 3 (HEAD-shift mid-`git switch`)
+
+This tick's authoring captured a NEW empirical sub-case of the multi-Otto
+contamination class:
+
+1. `git switch -c otto-cli-tick-shard-1644z-cascade-tail-complete-2026-05-16 origin/main`
+   succeeded — fresh branch from origin/main, peer WIP carried in worktree.
+2. Between the next Bash-tool call, peer Otto's `git switch` operation
+   moved HEAD to `otto-cli-shard-1618z-b0549-audit-unique-2026-05-16`
+   (per reflog `HEAD@{4}`).
+3. I then ran `git reset --hard origin/main` thinking I was on my new
+   branch — actually was on peer's. **The reset destroyed peer's local
+   branch state** (`e610e12` + `64b61d5` commits).
+4. Recovered via `git reset --hard e610e12` from reflog.
+
+**Damage scope:**
+
+- Local only — peer's branch on origin unchanged
+- Peer can `git fetch + git reset --hard origin/<branch>` to recover from
+  their session
+- Cost: ~5 GraphQL + 2 min of session time
+
+**Substrate-honest catch:** even with `git branch --show-current`
+discipline in place (caught HEAD-shift twice this session), the BETWEEN-
+Bash-tool-call HEAD shifts can still bite if the agent doesn't re-verify
+on EVERY mutating operation, not just before commit.
+
+**Reinforced discipline:** `git branch --show-current` immediately BEFORE
+any `git reset --hard`, not only before `git commit`. The catch needs to
+fire at every mutating-action boundary.
+
+## Speculative work — light tick by design
+
+Cascade complete; no further substantive work. This shard documents the
+arc + the recoverable-contamination Pattern 3 finding.
+
+## Real-dependency-waits active
+
+None — cascade complete.
+
+## Composes with
+
+- [1535Z shard](1535Z.md)
+- [1547Z shard](1547Z.md)
+- [1610Z shard + path-depth ref table](1610Z.md)
+- [1634Z cascade-complete shard](1634Z.md)
+- [`docs/AUTONOMOUS-LOOP-PER-TICK.md`](../../../../../AUTONOMOUS-LOOP-PER-TICK.md)
+- [`.claude/rules/zeta-expected-branch.md`](../../../../../../.claude/rules/zeta-expected-branch.md)
+  (the discipline this tick reinforces at additional mutating boundaries)
+- [`.claude/rules/claim-acquire-before-worktree-work.md`](../../../../../../.claude/rules/claim-acquire-before-worktree-work.md)
+  (Pattern 3 of saturation-ceiling; recoverable damage)
+- [B-0519](../../../../../backlog/P3/B-0519-multi-otto-branch-state-contamination-rca-2026-05-14.md)
+  (multi-Otto contamination RCA)