From 58e218650666766f7d9695e2bfdad6ab6571908b Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 24 Jul 2026 09:18:56 +0000
Subject: [PATCH] =?UTF-8?q?Re-point=20a=20fuel-agnostic=20gas=20boiler=20t?=
 =?UTF-8?q?o=20oil=20or=20solid=20fuel=20by=20main=5Ffuel=20=F0=9F=9F=A9?=
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Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 .../property/landlord_override_overlays.py    | 49 ++++++++++++++++++-
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/repositories/property/landlord_override_overlays.py b/repositories/property/landlord_override_overlays.py
index 3d1fcdce5..e987f7b26 100644
--- a/repositories/property/landlord_override_overlays.py
+++ b/repositories/property/landlord_override_overlays.py
@@ -106,12 +106,57 @@ _FUEL_FAMILY: dict[int, str] = {
     27: "lpg", 3: "lpg", 17: "lpg",
     28: "oil",
     29: "electricity", 25: "electricity",
-    33: "solid", 15: "solid", 10: "solid", 31: "solid",
+    # Solid fuels — house coal 33, smokeless 15, dual mineral/wood 10, plus wood
+    # logs (main_fuel_overlay code 6): omitting 6 left a wood-logs dwelling with no
+    # fuel family, so `resolve_boiler_archetype` never re-pointed it and
+    # `flag_fuel_mismatch` never checked it (ADR-0067).
+    33: "solid", 15: "solid", 10: "solid", 31: "solid", 6: "solid",
 }
 
 
+# A fuel-agnostic gas wet-boiler archetype re-points to the oil / solid-fuel
+# member matching the property's `main_fuel` family (ADR-0067). Oil preserves the
+# regular/combi split; any solid fuel (coal / wood / dual) collapses to the single
+# `Solid fuel boiler` member. Gas/LPG (RdSAP models LPG on gas), electric, and a
+# missing fuel leave the archetype unchanged, as does any non-gas-boiler archetype.
+_GAS_BOILER_REPOINT: dict[tuple[str, str], str] = {
+    ("Gas boiler, regular", "oil"): "Oil boiler, regular",
+    ("Gas boiler, combi", "oil"): "Oil boiler, combi",
+    ("Gas boiler, regular", "solid"): "Solid fuel boiler",
+    ("Gas boiler, combi", "solid"): "Solid fuel boiler",
+}
+
+
+def _fuel_family_of(fuel_value: Optional[str]) -> Optional[str]:
+    """The coarse fuel family a landlord `main_fuel` value resolves to (via the
+    fuel overlay's RdSAP code), or None when absent / unmapped."""
+    if fuel_value is None:
+        return None
+    fuel_overlay = fuel_overlay_for(fuel_value, 0)
+    code = (
+        fuel_overlay.heating.main_fuel_type
+        if fuel_overlay is not None and fuel_overlay.heating is not None
+        else None
+    )
+    if not isinstance(code, int):
+        return None
+    return _FUEL_FAMILY.get(code)
+
+
 def resolve_boiler_archetype(heating_value: str, fuel_value: Optional[str]) -> str:
-    raise NotImplementedError
+    """Re-point a fuel-agnostic gas wet-boiler archetype to the oil / solid-fuel
+    member matching the property's `main_fuel` (ADR-0067).
+
+    The landlord's boiler description cannot name its fuel, so the LLM defaults a
+    plain "Boiler … Regular/Combi" to the gas archetype; this join corrects it at
+    resolution using the sibling `main_fuel` override — the same rule as the
+    per-property backfill. Non-gas-boiler archetypes, gas/LPG fuels, and a missing
+    fuel are returned unchanged. Extensible to a future `Boiler, unspecified fuel`
+    member (fuel override → EPC → default gas)."""
+    family = _fuel_family_of(fuel_value)
+    if family is None:
+        return heating_value
+    return _GAS_BOILER_REPOINT.get((heating_value, family), heating_value)
 
 
 def _override_value(overrides: ResolvedPropertyOverrides, component: str) -> Optional[str]: