radar: pass 9 — content is live persist/log exemplar (append+replay-to-seq); W4 = 1 correct + 2 fakes to migrate

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plans/abstractions.md

@@ -12,6 +12,11 @@ Anything short → _Watching_ (what's missing) or _Rejected_ (why).
 
 ## Last scan
 
+- **Date:** 2026-06-07 (radar loop, pass 9)
+- **Pass 9:** `commerce` + `content` reached Phase 2 (`content` 162/162). **Key find:
+  `content` built its op log directly on `persist/log`** (backend-injected, append+replay-
+  to-seq) — the live reference exemplar for W4 (see W4). `events` MONTHLY RRULE,
+  `identity` OAuth2 auth-code + PKCE, search boolean-filtered ranked. A1 still 6 adopters.
 - **Date:** 2026-06-06 (radar loop, pass 8)
 - **Pass 8 — fleet expanded by 4 app-domain loops** (the briefing's anticipated
   `commerce`/`identity` arrivals, auto-picked up by dynamic discovery). All early-stage,
@@ -193,6 +198,17 @@ Anything short → _Watching_ (what's missing) or _Rejected_ (why).
 - **Migration is becoming concrete:** new `host-persist` loop (worktree + tmux, pass 6)
   is building the durable-storage host adapter persist was blocked on — once it lands,
   acl/mod can actually swap to `persist/log`.
+- **LIVE REFERENCE EXEMPLAR (pass 9): `content` already does it right.** `content`
+  (Phase 2 complete, 162/162) built its op log directly on `persist/log` instead of
+  faking it — `content/lib/content/store.sx`: backend injected via `(persist/open)`
+  ("content knows nothing about which backend", :10); append op as event
+  `persist/append b (content/-stream doc-id) …` (:20); read `persist/read` (:36);
+  `persist/last-seq` (:47); **version = replay op stream up to a seq**
+  (filter `persist/event-seq ev <= seq`, :61). "The op log is the source of truth …
+  the materialised doc is a cache, never primary state."
+  This proves the W4 target is real, not hypothetical: acl + mod's hand-rolled
+  monotonic-seq logs should adopt exactly content's `persist/log` pattern. **W4 now =
+  1 correct exemplar (content) + 2 fakes to migrate (acl, mod).**
 
 ### W5 · Proof-tree explanation over a logic-program derivation
 - `acl/lib/acl/explain.sx` (reconstructs a canonical proof by goal-directed search over a