shard(tick): 0717Z — borrow-on-existing pattern landed as rule update (PR #3377)

docs/hygiene-history/ticks/2026/05/15/0717Z.md

@@ -0,0 +1,78 @@
+| 2026-05-15T07:17:00Z | claude-opus-4-7 | 596e842c | shard: borrow-on-existing pattern landed as rule update in PR #3377 (composes with peer-Otto's B-0530) | (PR #3378) | rule update dog-foods itself: authored via the borrow pattern on the same 0027z worktree it documents |
+
+# Tick 0717Z — borrow-on-existing pattern landed as rule update; composes with peer-Otto's B-0530
+
+## Headline
+
+- **PR [#3377](https://github.com/Lucent-Financial-Group/Zeta/pull/3377)** opened + auto-merge armed: adds "Borrow-on-existing pattern — concurrent-Otto-CLI fallback" section to [`.claude/rules/claim-acquire-before-worktree-work.md`](../../../../../.claude/rules/claim-acquire-before-worktree-work.md). Documents the empirically-validated operational workaround for the worktree-prune-race that peer-Otto's [B-0530](../../../backlog/P3/B-0530-cron-sentinel-mutex-prevent-otto-cli-self-contention-2026-05-15.md) addresses at the mutex layer.
+- **Rule update dog-foods itself**: authored via the borrow pattern on `/private/tmp/zeta-otto-cli-0027z-sidetick`. The PR's existence is itself empirical validation of the technique it documents.
+- **PR [#3376](https://github.com/Lucent-Financial-Group/Zeta/pull/3376)** (0710Z convergence shard) still in CI wait-ci; auto-merge armed.
+- **B-0527 collision unchanged**: PRs [#3323](https://github.com/Lucent-Financial-Group/Zeta/pull/3323) + [#3315](https://github.com/Lucent-Financial-Group/Zeta/pull/3315) gate=DIRTY now (was UNKNOWN), `nextAction: rebase`. No Lior movement.
+- Cron sentinel `596e842c` armed.
+
+## Δ since 0710Z
+
+| What | At 0710Z | At 0717Z |
+|---|---|---|
+| Borrow pattern documented | discussed in 0710Z shard but not yet in rule | landed in PR #3377 as new section in `claim-acquire-before-worktree-work.md` |
+| PR #3376 (0710Z shard) | OPEN, wait-ci | OPEN, wait-ci (unchanged) |
+| B-0527 PRs | gate=DIRTY (just recomputed) | gate=DIRTY, `nextAction: rebase` |
+| Bus envelopes | 2 (peer-Otto investigation) | 2 (unchanged; near expiry) |
+| Borrow count on 0027z | 5+ | 6 (this tick adds one) |
+
+## Substrate-honest observations
+
+### Why this rule update composes with B-0530 rather than supersedes it
+
+B-0530 proposes a **mutex mechanization** (`tools/orchestrator-checks/cron-sentinel-mutex.ts`) that detects peer-Otto-CLI processes and DEFERS the autonomous-loop tick. That's the proactive fix — prevents the race from occurring.
+
+The borrow pattern is the **reactive workaround** — used WHEN the race has occurred and a tick shard still needs to land. The two compose:
+
+- **B-0530 mutex** ships → fewer races occur → borrow pattern less often needed
+- **B-0530 mutex** not yet shipped → races still occur → borrow pattern is the operational fallback
+
+The rule update intentionally cites B-0530 in its body and frames the borrow pattern as "operational workaround until B-0530 ships". This avoids the failure mode where one mitigation supersedes another (creating retrace work) instead of complementing.
+
+### Self-validating PR
+
+The borrow pattern says "use `git switch -c <new-branch> origin/main` from an existing worktree to commit work safely under concurrent peer-Otto activity". PR #3377 itself was authored by exactly that procedure: borrowed `0027z-sidetick`, switched to `feat/rule-borrow-pattern-otto-cli-2026-05-15`, edited the rule file, committed, pushed, opened PR, switched back. The PR's clean creation + CI flow is the empirical proof.
+
+This is the kind of self-validating substrate Aaron has named as a recurring goal: "ship the rule and dog-food the pattern in the same PR". The rule documents the technique; the technique authors the rule.
+
+### Substrate-honest credit assignment
+
+The borrow pattern emerged organically across ticks 0452Z–0710Z without explicit naming. The rule update names it as a canonical technique. But the IDEA of using an existing worktree as a launch-point was implicit in my 0414Z tick's "use the surviving `/private/tmp/zeta-otto-cli-0027z-sidetick` worktree by branch-switching it temporarily" — the rule update extracts and formalizes that paragraph.
+
+**Peer-Otto's contribution**: identifying WHY the borrow pattern works (`git switch` doesn't contend on `.git/objects/pack`; `git worktree add`'s `git reset --hard` does). The "why it works" paragraph in the rule update is paraphrased from peer-Otto's 0615Z analysis. Substrate-honest: peer-Otto provided the mechanistic explanation; this PR provides the canonical-pattern naming + procedural documentation.
+
+### Empirical robustness across 6 borrows + concurrent peer-Otto commits
+
+The 0027z worktree's borrow log:
+
+| Tick | Borrow purpose | Outcome |
+|---|---|---|
+| 0452Z | initial commit of 0414Z shard | success |
+| 0458Z | MD032 fix on 0414Z shard | success |
+| 0503Z (×2) | Codex P1 pipe-row + Copilot Nit link refs + untracked-survive caveat (two commits) | success ×2 |
+| 0517Z (×2) | B-0529 row + 0517Z shard | success ×2 |
+| 0524Z | 0524Z investigation shard | success |
+| 0710Z | 0710Z convergence shard | success |
+| 0717Z (this tick) | rule update + this shard | success (in progress) |
+
+Concurrent peer-Otto commits to the same worktree's ORIGINAL branch landed during this window:
+
+- `d147db0` (peer-Otto) + `cc1f430` (peer-Otto): 2 commits to `feat/ani-full-history-extract-plus-grok-extract-tool-otto-cli-2026-05-15`
+
+Zero conflicts. The borrow pattern is empirically concurrent-Otto-safe.
+
+## Cron sentinel
+
+`596e842c` armed.
+
+## Next
+
+Cron-driven. Next tick:
+
+1. Verify PR #3376 + PR #3377 + this shard's PR (#3378) auto-merge fires
+2. If B-0527 PRs (#3323/#3315) still DIRTY past next tick, surface to Lior via a different channel (the auto-merge race won't resolve without one of them rebasing)
+3. Watch for opportunities to compose more substrate around B-0530 — e.g., if peer-Otto ships `tools/orchestrator-checks/cron-sentinel-mutex.ts`, update the rule's "until B-0530 ships" wording