diff --git a/decisions/architecture.md b/decisions/architecture.md
index d46c9abc6..2aa135550 100644
--- a/decisions/architecture.md
+++ b/decisions/architecture.md
@@ -700,12 +700,13 @@ Technical foundation decisions that constrain implementation: engine, client-ser
   - 3 navigation levels: system picker → orbital diagram → body atlas (heightmap + overlays)
   - Heightmap displayed as `Texture2D` with pan/zoom
   - Marker overlay renders cities, roads, rail, POIs, named features on top of heightmap
-  - Click city → City Data Panel (name, population, currency zone, Commission presence, shadow economy zone, gate distance, economics panel link)
+  - Click city → City Data Panel (name, population, currency zone, Commission presence, gate distance, economics panel link) — shadow economy zone dropped per §7 amendment (2026-05-22)
   - Economics panel link: click-through to Phase 2 economics panel pre-filtered to that node — primary Phase 2/3 integration point
 
-  **7. Overlay System — 9 MVP Overlays**
+  **7. Overlay System — 8 MVP Overlays**
+  - **Amendment (2026-05-22):** dropped the `shadow economy` toggleable overlay (9 → 8 overlays). Shadow economy is an *underwater simulation modifier* — `shadow_economy_intensity` (D-174) feeds derived signals such as `collection_efficiency` and signal 7 `official_coverage_ratio` (D-181), but it is not a user-navigable data point, so it does not warrant a player-facing atlas overlay or City Data Panel field. The simulation layer (D-174) is unaffected. Also removed from §6 (city data panel) and §10 (completion criteria) for consistency.
   - 5 always-on: terrain, infrastructure, named features, gate/spaceport POIs, political zones
-  - 4 toggleable: population density, production zones, shadow economy zones (broad bands), corporate presence (Tier 1 only)
+  - 3 toggleable: population density, production zones, corporate presence (Tier 1 only)
   - Deferred overlays visible in toggle bar but locked with unlock requirements shown on hover (creates pull toward Phase 4+ systems)
   - Maps to D-181 signal visibility ladder
 
@@ -740,7 +741,7 @@ Technical foundation decisions that constrain implementation: engine, client-ser
   3. Population-scaled depth (core systems rich, frontier sparse)
   4. City data panel works (click any city, see data + economics link)
   5. Economics panel integration works (link opens Phase 2 panel filtered to node)
-  6. All 9 MVP overlays present and functional
+  6. All 8 MVP overlays present and functional
   7. Atlas is read-only (no verbs execute from map)
   8. Stations show at system view with mini data panel (no drill-down)