diff --git a/docs/BACKLOG.md b/docs/BACKLOG.md
index 4659c6bd6..da850f7d3 100644
--- a/docs/BACKLOG.md
+++ b/docs/BACKLOG.md
@@ -665,7 +665,7 @@ are closed (status: closed in frontmatter)._
 - [ ] **[B-0395](backlog/P3/B-0395-operational-resonance-conversation-interface-path-a-browser-local-llm-2026-05-09.md)** Conversation interface Path A — embed browser/local LLM (WebLLM or transformers.js) in dashboard for in-context review discussion
 - [ ] **[B-0422](backlog/P3/B-0422-clifford-algebraic-narrative-engine-pauli-symmetry-breaking-falsifiability-test-2026-05-12.md)** Clifford-algebraic narrative engine for testing the Pauli-symmetry-breaking-from-agenda-conservation prediction (research target identified by DeepSeek 2026-05-12)
 - [ ] **[B-0499](backlog/P3/B-0499-z-of-i-dbsp-refinement-cartesian-dualism-2026-05-14.md)** Z[i]-weighted DBSP refinement — Cartesian-dualism candidate from afternoon-cascade
-- [ ] **[B-0506](backlog/P3/B-0506-stale-worktree-prune-cadence-mechanization-2026-05-14.md)** Stale-worktree prune cadence — mechanize `git worktree prune --expire=now`
+- [x] **[B-0506](backlog/P3/B-0506-stale-worktree-prune-cadence-mechanization-2026-05-14.md)** Stale-worktree prune cadence — mechanize `git worktree prune --expire=now`
 - [ ] **[B-0514](backlog/P3/B-0514-author-missing-wwjd-grey-honest-memory-file-2026-05-14.md)** Author missing memory file: feedback_aaron_wwjd_keeps_the_grey_in_aaron_honest_devil_lives_in_the_grey_in_numbers_2026_05_12.md
 - [ ] **[B-0515](backlog/P3/B-0515-architecture-as-externalization-of-aarons-dialectical-perception-dashboard-target-shift-2026-05-14.md)** Architecture-as-externalization-of-Aaron's-dialectical-perception — dashboard acceptance criteria target shift
 - [ ] **[B-0517](backlog/P3/B-0517-memory-md-index-bloat-cleanup-cadence-2026-05-14.md)** MEMORY.md index bloat cleanup + entry-length enforcement cadence
diff --git a/docs/backlog/P3/B-0506-stale-worktree-prune-cadence-mechanization-2026-05-14.md b/docs/backlog/P3/B-0506-stale-worktree-prune-cadence-mechanization-2026-05-14.md
index b41567a03..2d9129817 100644
--- a/docs/backlog/P3/B-0506-stale-worktree-prune-cadence-mechanization-2026-05-14.md
+++ b/docs/backlog/P3/B-0506-stale-worktree-prune-cadence-mechanization-2026-05-14.md
@@ -1,12 +1,13 @@
 ---
 id: B-0506
 priority: P3
-status: open
+status: closed
 title: "Stale-worktree prune cadence — mechanize `git worktree prune --expire=now`"
 tier: factory-hygiene
 effort: S
 created: 2026-05-14
-last_updated: 2026-05-14
+last_updated: 2026-05-16
+closed: 2026-05-16
 depends_on: []
 composes_with: [B-0400, B-0444]
 tags: [worktree, hygiene, factory-cadence, multi-foreground-surface, friction-reducer]
@@ -65,3 +66,22 @@ This is a P3 friction-reducer, not a P0 substrate gap. The cleanup is straightfo
 ## Origin tick
 
 `docs/hygiene-history/ticks/2026/05/14/1817Z.md` — this tick's shard documents the empirical observation and the manual cleanup.
+
+## Resolution (2026-05-16)
+
+Mechanization shipped 2026-05-14 via **PR #3225** (`feat(B-0506): mechanize stale-worktree audit — audit-stale-worktrees.ts (clean branch)`, merged).
+
+The shipped tool [`tools/hygiene/audit-stale-worktrees.ts`](../../../tools/hygiene/audit-stale-worktrees.ts) implements every behavior named in "Proposed mechanization" above:
+
+| Specified behavior | Status |
+|---|---|
+| Enumerate via `git worktree list --porcelain` | shipped |
+| Existence-check each working-tree path | shipped |
+| Markdown summary report (`--report PATH`) | shipped |
+| `--prune` runs `git worktree prune --expire=now -v` | shipped |
+| Exit codes (0 / 64 / 128) | shipped |
+| DST-friendly (only timestamp non-deterministic) | shipped |
+
+Phase 2 (GHA cron wire-up + per-Otto-process worktree isolation) is **out of scope** per the tool's own header comment and would compose with `factory-hygiene-audit-cadence.yml` if/when needed; that's a separate row, not a B-0506 obligation.
+
+Row left open from 2026-05-14 to 2026-05-16 due to substrate drift — the mechanization PR landed but this row was never marked closed. Caught this tick by Otto-CLI 2026-05-16T04:19Z while picking a P3 friction-reducer; tried to claim+implement, discovered the tool already existed at the proposed path. Closing instead.