diff --git a/workplans/HUB-WP-0004-runtime-and-extension-contract.md b/workplans/HUB-WP-0004-runtime-and-extension-contract.md
index 817271f..1fa154d 100644
--- a/workplans/HUB-WP-0004-runtime-and-extension-contract.md
+++ b/workplans/HUB-WP-0004-runtime-and-extension-contract.md
@@ -8,7 +8,7 @@ status: proposed
 owner: codex
 topic_slug: infotech
 created: "2026-08-09"
-updated: "2026-08-09"
+updated: "2026-08-20"
 parent_project: prj-state-hub-retirement
 parent_workplan: SHR-WP-0001
 related:
@@ -28,7 +28,8 @@ and runtime**, shipping `helixforge.hub-extension` Tier 1 artefacts and a clear
 path to absorb core-hub production traffic.
 
 Coordinated by `prj-state-hub-retirement` (SHR-WP-0001). Architecture:
-`architecture/hub-extension-architecture_v0.1.md`.
+`prj-state-hub-retirement/architecture/hub-extension-architecture_v0.1.md`
+(the path is project-relative; hub-core has no `architecture/` directory).
 
 ## Adopt project architecture freeze
 
@@ -106,6 +107,51 @@ state_hub_task_id: "b35fff11-ac5a-4d70-9f54-416331baea87"
 With CORE-WP-0010, document route/module move order for `/api/v2`, dual-run, and
 cutover criteria. No big-bang.
 
+## Readiness review (2026-08-20)
+
+Reviewed against current repo state at the request of `STATE-WP-0079`, which is
+blocked on this plan. **Nothing structurally prevents `ready`** — the plan has
+sat at `proposed` since it was drafted on 2026-08-09 without a review, rather
+than because it is blocked.
+
+**Why this matters now.** Wave B of the State Hub cutover slice plan
+(`state-hub/docs/retirement-cutover-slice-plan.md`) is **125 inventory items**
+across catalogs, messaging, telemetry, projections and hub UI, and none of it
+can start until this plan leaves `proposed`. It is currently the single largest
+gate in the retirement program.
+
+**Referenced artefacts all exist** in `prj-state-hub-retirement/architecture/`:
+
+| Artefact | ID |
+| --- | --- |
+| `information-model_v0.1.md` | SHR-ARCH-IA-0001 |
+| `hub-extension-architecture_v0.1.md` | SHR-ARCH-HUB-0001 |
+| `hub-extension-contract_v0.1.yaml` | — (T02 input) |
+| `retirement-gates_v0.1.md` | gate definitions |
+
+**Current hub-core surface**, relevant to T04's minimal vertical:
+
+| Requested port | Plausible existing basis |
+| --- | --- |
+| `port.registry` | `routers/repos.py`, `routers/domains.py`, `routers/capabilities.py` |
+| `port.messaging` | `routers/messages.py` |
+| `port.events.progress` | `routers/progress.py` |
+| `port.events.interaction` | none obvious |
+| `port.projection.query` | none obvious |
+
+Mapping needs owner confirmation — `port.*` appears nowhere in hub-core outside
+this workplan, so the vocabulary has not landed yet. That is T01's job, and T01
+is a review task with its inputs already available, so it can start immediately.
+
+**Suggested sequencing:** T01 (inputs ready) → T03 (packaging decision, unblocks
+T04's shape) → T02 and T04 in parallel → T05 → T06 with CORE-WP-0010.
+
+Two of the five ports have no existing basis, so T04's "minimal vertical" is
+partly greenfield; worth sizing before committing to it.
+
+*Review by Claude Code from the state-hub session; status left at `proposed` for
+the owner to flip.*
+
 ## Acceptance
 
 - [ ] Architecture freeze acknowledged in INTENT/SCOPE