ADR-016: deployment honesty — no runtime capability surface; compile-time identity + matrix (OQ-08 resolved)

docs/architecture/engine-postgres.md

@@ -1,6 +1,6 @@
 ---
 status: draft
-last_updated: 2026-10-05
+last_updated: 2026-10-06
 ---
 
 # Postgres engine
@@ -111,6 +111,7 @@ the record in [ADR-003](decisions/003-sqlite-driver.md).
 | [012](decisions/012-forked-substrate-design.md) | Fork design | contract-blind substrate (SQLite side); pg engine owns its own curve/stamps arithmetic, equivalence pinned by the contract suite |
 | [014](decisions/014-outbox-tx-enqueue.md) | Outbox tx enqueue | `outbox_enqueue_tx` on `TxHandle`; derivation engine-side inside the caller's tx |
 | [015](decisions/015-streams-depth.md) | Streams depth | nullable key column (carried metadata); bigserial offsets, global-FIFO reads; keyed tx publish; `trim_to` as a pool-connection delete |
+| [016](decisions/016-deployment-honesty.md) | Deployment honesty | no runtime capability surface — this engine's multi-host posture is stated by its crate identity and docs; `PayloadTooLarge` occurrence pinned contract-suite (this engine produces it, client-side pre-round-trip) |
 
 ## Open Questions
 
@@ -118,8 +119,12 @@ Open questions are tracked in
 [open-questions.md](open-questions.md). Key
 questions affecting this document:
 
-- **OQ-08**: capability surface (shared with
-  [deployment.md](deployment.md)) (open)
+- **OQ-08**: capability surface — **resolved**
+  (2026-10-06, [ADR-016](decisions/016-deployment-honesty.md)):
+  no runtime capability surface; this engine's multi-host posture
+  lives in its crate identity + docs and the deployment matrix;
+  the engine's one runtime-visible asymmetry (`PayloadTooLarge`)
+  was already contract-pinned.
 - **OQ-12**: streams depth — **resolved**
   (2026-10-05, [ADR-015](decisions/015-streams-depth.md)): key =
   carried metadata; global-FIFO-by-offset ordering row
@@ -130,6 +135,8 @@ questions affecting this document:
 
 Resolved: **OQ-09** (scheduler collapse —
 [ADR-009](decisions/009-scheduler-collapse.md)), **OQ-05** (queue
-semantics depth — [ADR-010](decisions/010-queue-semantics-depth.md)), and
+semantics depth — [ADR-010](decisions/010-queue-semantics-depth.md)),
 **OQ-12** (streams depth — [ADR-015](decisions/015-streams-depth.md)),
-2026-10-05.
+and **OQ-08** (capability surface — none;
+[ADR-016](decisions/016-deployment-honesty.md)),
+2026-10-05/06.