diff --git a/docs/hygiene-history/ticks/2026/05/16/0520Z.md b/docs/hygiene-history/ticks/2026/05/16/0520Z.md
new file mode 100644
index 000000000..e2dde762c
--- /dev/null
+++ b/docs/hygiene-history/ticks/2026/05/16/0520Z.md
@@ -0,0 +1,69 @@
+# Tick 2026-05-16T05:20Z — Otto-CLI
+
+Ninth tick of the resume-session series. Brief-ack #2 of session
+(real bounded named-dependencies on PRs #3746, #3750, #3753).
+Investigated remaining 2 threads on PR #3746; both are
+not-actionable (viewpoint difference + peer's content). Posted
+an [explanatory comment](https://github.com/Lucent-Financial-Group/Zeta/pull/3746#issuecomment-4465795335)
+on PR #3746 documenting why the rule extension stays as-is and
+auto-merge remains armed. Caught another instance of the
+multi-Otto HEAD-desync pattern live during the investigation.
+
+## Refresh result
+
+| Surface | State |
+|---|---|
+| Cron sentinel | Alive (`bd1c7739`) |
+| Rate limit (GraphQL) | 1266/5000 remaining (used 3734); reset in ~50 min |
+| `origin/main` | Advanced to `f4ac125` — PR #3748 (memory file) merged |
+| PR #3746 (rule extension) | 2 unresolved threads; auto-merge armed; viewpoint-difference + peer's content |
+| PR #3750 (peer's B-0553 row) | Peer landed `f546dba fix(B-0553): address Copilot + Codex review threads` locally; not yet pushed |
+| PR #3753 (last tick shard) | wait-ci |
+
+## Investigation: the 2 remaining PR #3746 threads
+
+| Thread | Class | Action |
+|---|---|---|
+| `PRRT_kwDOSF9kNM6Ch2oT` (line 50, actor attribution B-0528/B-0535) | **Viewpoint difference, not factual error** — rule's text records from Otto-CLI lane; 0448Z shard records from Otto-Desktop lane; both match git authorship on `origin/main` | **Not actionable**; explanatory comment posted; auto-merge stays armed |
+| `PRRT_kwDOSF9kNM6Ch2of` (line 20, 0448Z shard line-count off-by-one) | **Peer's content** — bundled into PR but authored by peer Otto-Desktop | **Left to peer** per `honor-those-that-came-before` |
+
+The substrate-honest framing: the rule's empirical anchor explicitly says "Otto-CLI + Otto-Desktop closed 4 drift rows" — the multi-lane attribution IS intentional. Copilot detected a surface-level discrepancy between two correct-from-their-perspective records and flagged it. The fix is to acknowledge in a PR comment, not edit the content. Auto-merge stays armed; the threads block merge only because of `required_conversation_resolution` policy.
+
+## Live capture: HEAD-desync pattern (from the memory file)
+
+While investigating PR #3746's branch state, peer Otto-Desktop landed `f546dba fix(B-0553): address Copilot + Codex review threads on PR #3750` LOCALLY on their `backlog/b0553-audit-backlog-status-drift-otto-cli-2026-05-16` branch. The commit was made via `git switch backlog/b0553-...` while I was still investigating the rule extension branch.
+
+When I checked refs:
+
+```text
+HEAD                                              = f546dba (peer's B-0553 fix)
+chore/backlog-item-close-gate-otto-cli-2026-05-16 = 18ca3c1 (my last rule commit)
+backlog/b0553-audit-backlog-status-drift-otto-cli-2026-05-16 = f546dba
+```
+
+`git branch --show-current` returned `backlog/b0553-...` — peer switched the worktree during my Bash invocations. This matches exactly the **Multi-Otto HEAD desync** failure mode I documented in the merged memory file (`memory/feedback_substrate_drift_catch_pattern_...md`). The discipline applies: switch back to a known-good branch explicitly before each Bash command, and verify `git branch --show-current` before any commit.
+
+## Why brief-ack #2 is correct here
+
+Per counter-with-escalation in [`.claude/rules/holding-without-named-dependency-is-standing-by-failure.md`](../../../../../../.claude/rules/holding-without-named-dependency-is-standing-by-failure.md):
+
+- 1-2 brief-acks acceptable when real bounded named dependencies exist
+- 3 of my PRs in legitimate CI / thread-resolution waits (PR #3746, #3750, #3753)
+- Rate limit at 1266/5000 — also a real cost-awareness signal to avoid heavy `gh` use
+
+Choosing **triage existing PR** + **explanatory comment** + **brief-ack shard** over opening another PR is the right substrate-cost tradeoff at the current queue depth and rate-limit budget.
+
+## Real-dependency-waits active
+
+- PR #3746 — 2 not-actionable threads (viewpoint + peer's content); waiting for peer to push their B-0553 fix which may auto-resolve PR #3746's threads or for `required_conversation_resolution` to soften
+- PR #3750 — peer's B-0553 row; peer landed local fix `f546dba`; awaiting peer to push
+- PR #3753 — this session's 0516Z shard; wait-ci
+
+## Visibility signal
+
+- Explanatory comment posted on PR #3746 (no content edit; auto-merge stays armed)
+- HEAD-desync pattern live-validated again (multi-Otto contention; recoverable)
+- Sentinel `bd1c7739` alive
+- Rate limit budget noted (1266/5000); next-tick should minimize `gh` calls until reset
+
+Stopping foreground; cron will fire the next tick.