09 §3 decision 43 (claper -> PG 17, CC unattended); CONTEXT

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

documentation/architecture/09-update-architecture.md

@@ -477,6 +477,14 @@ R-636's louder repeated alarm.
     two WHEN the upstream runs the newer major — paperless's does (18, Django ~5.2.5, psycopg 3); tandoor's does not,
     and 17 is the newest major its Django documents, with no mount change. Read 2026-09-27 from each upstream's
     compose and requirements (`audits/version-travel-2026-09-26/B/`). Reversible: the catalog pins the major.
+43. **claper → PostgreSQL 17; calcom not moved** — *decided by CC unattended 2026-09-28 — operator may reverse.*
+    *One sentence:* which major does claper's conversion target? **Options:** (a) 17 — no mount change; (b) 18 —
+    the mount moves to `/var/lib/postgresql`. **Costs:** (a) a later second conversion if claper's upstream moves to
+    18; (b) claper would run a major its own upstream compose (`postgres:15`, v2.5.0) has not run. **Why (a):**
+    decision 42's rule — the newer major only when the app's own upstream runs it; claper's does not. Proven on both
+    venues (bench: 32 tables equal, peaks 75.8 %/78.3 %; box 9202: converted through the guarded Update in 7.2 s),
+    catalog `4a249b9`, `audits/pg-calcom-claper-2026-09-28/`. **calcom** is not moved: its FROM version does not
+    start at the catalog's memory limit (R-703), so no conversion can be proven. Reversible: the catalog pins the major.
 
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