diff --git a/docs/adr/0019-wall-insulation-eligibility.md b/docs/adr/0019-wall-insulation-eligibility.md
index 937ce79f..e77eebee 100644
--- a/docs/adr/0019-wall-insulation-eligibility.md
+++ b/docs/adr/0019-wall-insulation-eligibility.md
@@ -6,7 +6,7 @@ The solid-wall Recommendation Generator must decide, per Property, which wall-in
 
 **By construction** (keyed on the `wall_construction` code, which is consistent across the API and Elmhurst paths for codes 1-5; the wall *description* is empty on the Elmhurst ingestion path so it can't be the primary signal — it's a fallback for the ambiguous codes (cob 7) and for refining the as-built trigger on the API path).
 
-**System-built** is keyed on `wall_construction == 6` (`WALL_SYSTEM_BUILT`; the Elmhurst `SY System build` label). This code is currently *overloaded*: `B Basement wall` also maps to 6 (`BASEMENT_WALL_CONSTRUCTION_CODE`, `mapper.py:2100`), so the generator additionally guards on `main_wall_is_basement` — a basement wall is never solid-wall-insulation-suitable and is excluded regardless of construction. Because `main_wall_is_basement` is presently derived as `wall_construction == 6`, *every* code-6 wall is treated as basement today, so the system-built branch is inert until the calculator disambiguates system-built from basement (target: MAIN `wall_construction == 6` with `main_wall_is_basement` False). The strict-xfail pin `test_system_built_generator_offers_ewi_and_iwi_each_pinning_its_after` is the tripwire for that fix. Note `wall_construction == 8` is **Park home** (`PH`) on the Elmhurst path, *not* system-built — do not key system-built on 8.
+**System-built** is keyed on `wall_construction == 6` (`WALL_SYSTEM_BUILT`; the Elmhurst `SY System build` label). This code is currently *overloaded*: `B Basement wall` also maps to 6 (`BASEMENT_WALL_CONSTRUCTION_CODE`, `mapper.py:2100`), so the generator additionally guards on `main_wall_is_basement` — a basement wall is never solid-wall-insulation-suitable and is excluded regardless of construction. Because `main_wall_is_basement` is presently derived as `wall_construction == 6`, *every* code-6 wall is treated as basement today, so the system-built branch is inert until the calculator disambiguates system-built from basement (target: MAIN `wall_construction == 6` with `main_wall_is_basement` False — tracked in Hestia-Homes/Model#1177). The strict-xfail pin `test_system_built_generator_offers_ewi_and_iwi_each_pinning_its_after` is the tripwire for that fix. Note `wall_construction == 8` is **Park home** (`PH`) on the Elmhurst path, *not* system-built — do not key system-built on 8.
 
 | Construction | Cavity fill | IWI | EWI |
 |---|---|---|---|
diff --git a/tests/domain/modelling/test_elmhurst_cascade_pins.py b/tests/domain/modelling/test_elmhurst_cascade_pins.py
index 97fccc84..5821b5c1 100644
--- a/tests/domain/modelling/test_elmhurst_cascade_pins.py
+++ b/tests/domain/modelling/test_elmhurst_cascade_pins.py
@@ -177,7 +177,8 @@ def test_solid_brick_generator_offers_ewi_and_iwi_each_pinning_its_after() -> No
 
 @pytest.mark.xfail(
     strict=True,
-    reason="Blocked on the calculator-side wall_construction=6 collision: "
+    reason="Blocked on Hestia-Homes/Model#1177 — the calculator-side "
+    "wall_construction=6 collision: "
     "Elmhurst 'SY System build' and 'B Basement wall' both map to 6 "
     "(mapper.py:2100), so `main_wall_is_basement` is wrongly True for "
     "system-built and the generator's basement guard suppresses it. Flips "