Lodge the heat-network SAP code and Table 12 community fuel for PasHub community heating 🟩

The extractor now captures "Heating System (Other):" and the mapper resolves
it to the Table 4a code (301, community boilers) + Table 12 community fuel
(51 via the shared _resolve_community_heating_fuel_code), so
is_heat_network_main routes the DLF / standing-charge / 80%-efficiency
branch instead of pricing the dwelling as an ordinary mains-gas boiler
(fixture 507644414148: +14.3 over-rate closes by ~8.6). Harness MAE
1.726 -> 1.684; ceiling ratcheted to 1.70.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/documents_parser/extractor.py

@@ -595,6 +595,8 @@ class PasHubRdSapSiteNotesExtractor:
             )
             or "",
             system_type=self._get_in(data, "System type:") or "",
+            community_heat_source=self._get_in(data, "Heating System (Other):")
+            or "",
             product_id=int(self._get_in(data, "Product Id") or 0),
             manufacturer=self._get_in(data, "Manufacturer") or "",
             model=self._get_in(data, "Model") or "",

backend/documents_parser/tests/test_extractor.py

@@ -718,7 +718,7 @@ class TestMainHeatingCommunityHeatSource:
         # Arrange — fixture 1's heating section with the community block
         # spliced in after its "Fuel:" lodgement.
         lines = load_text_fixture()
-        idx = lines.index("Fuel:")
+        idx = lines.index("System type:")
         spliced = (
             lines[: idx + 2]
             + ["Heating System (Other):", "Community heating - boilers only"]

backend/documents_parser/tests/test_pashub_sap_accuracy.py

@@ -93,7 +93,11 @@ _MIN_WITHIN_HALF: float = 0.18
 # under-rate closing.
 # Ratcheted 2.58 -> 2.55 by #1590 bug 3 (PV Connection label -> gov-API int:
 # "Not connected" no longer silently credited): observed MAE 2.538.
-_MAX_SAP_MAE: float = 1.75
+# Ratcheted 1.75 -> 1.70 by the dig-round-2 fixes: RIR surfaces billed with
+# the surveyed roof insulation + stud-wall commons, and community heating
+# lodging Table 4a code 301 + Table 12 fuel 51 (507644414148 computes on the
+# heat-network branch). Observed MAE 1.684.
+_MAX_SAP_MAE: float = 1.70
 
 _KNOWN_GAP_REASON = (
     "pashub `from_site_notes` mapper does not int-code a main-heating "

datatypes/epc/domain/mapper.py

@@ -6191,12 +6191,26 @@ def _map_sap_heating(
         else None
     )
 
+    # Heat networks lodge the Table 4a code + Table 12 community fuel from
+    # the community heat-source label; every other system resolves the plain
+    # Table 32 fuel (issue #1590 follow-up, fixture 507644414148).
+    community_sap_code: Optional[int] = None
+    main_fuel: Union[int, str]
+    if main.system_type.lower() in _PASHUB_HEAT_NETWORK_SYSTEM_TYPES:
+        community_sap_code, community_fuel = _pashub_community_heating(
+            main.community_heat_source, fuel_type
+        )
+        main_fuel = community_fuel if community_fuel is not None else fuel_type
+    else:
+        main_fuel = _pashub_main_fuel_code(fuel_type)
+
     return SapHeating(
         instantaneous_wwhrs=InstantaneousWwhrs(),
         main_heating_details=[
             MainHeatingDetail(
                 has_fghrs=main.flue_gas_heat_recovery_system,
-                main_fuel_type=_pashub_main_fuel_code(fuel_type),
+                main_fuel_type=main_fuel,
+                sap_main_heating_code=community_sap_code,
                 heat_emitter_type=_pashub_heat_emitter_code(main.emitter),
                 emitter_temperature=main.emitter_temperature,
                 fan_flue_present=main.fan_assist,
@@ -6265,6 +6279,37 @@ def _pashub_mechanical_ventilation_kind(
     return _PASHUB_VENTILATION_TYPE_TO_KIND[ventilation_type]
 
 
+# PasHub community heat-source label ("Heating System (Other)") → the
+# Table 4a heat-network SAP code that routes `is_heat_network_main` (DLF,
+# standing charge, 80% heat-source efficiency) and, via the shared Elmhurst
+# resolver, the Table 12 community fuel. Only the cohort's boilers-only
+# variant is lodged so far; CHP (302) / heat pump (304) join when observed.
+_PASHUB_COMMUNITY_HEAT_SOURCE_TO_SAP_CODE: Dict[str, int] = {
+    "Community heating - boilers only": 301,
+}
+_PASHUB_COMMUNITY_HEAT_SOURCE_TO_ELMHURST: Dict[str, str] = {
+    "Community heating - boilers only": "Boilers",
+}
+
+
+def _pashub_community_heating(
+    heat_source_label: str, fuel_label: str
+) -> tuple[int, Optional[int]]:
+    """Resolve a PasHub community-heating lodgement to its (Table 4a SAP
+    code, Table 12 fuel code) at the mapper boundary (ADR-0015), reusing
+    `_resolve_community_heating_fuel_code`. An uncovered heat-source label
+    strict-raises so the dwelling is never silently priced as an ordinary
+    boiler (issue #1590 follow-up, fixture 507644414148)."""
+    if heat_source_label not in _PASHUB_COMMUNITY_HEAT_SOURCE_TO_SAP_CODE:
+        raise UnmappedPasHubLabel("community heat source", heat_source_label)
+    sap_code = _PASHUB_COMMUNITY_HEAT_SOURCE_TO_SAP_CODE[heat_source_label]
+    fuel = _resolve_community_heating_fuel_code(
+        _PASHUB_COMMUNITY_HEAT_SOURCE_TO_ELMHURST[heat_source_label],
+        fuel_label,
+    )
+    return sap_code, fuel
+
+
 # PasHub surveyed §Water-Heating "Cylinder Size" band → SAP10 cylinder-size
 # enum (Table 28: 2=Normal/110L, 3=Medium/160L, 4=Large/210L). PasHub renders
 # the band with its own litre-range suffix (unlike the Elmhurst forms in

datatypes/epc/domain/tests/test_from_site_notes.py

@@ -1802,10 +1802,14 @@ class TestPasHubMainHeatingControlCoding:
         )
 
         raw = load("pashub_rdsap_site_notes_example1.json")
-        raw["heating_and_hot_water"]["main_heating"][
-            "system_type"
-        ] = "Community heating system"
-        raw["heating_and_hot_water"]["main_heating"]["controls"] = (
+        mh = raw["heating_and_hot_water"]["main_heating"]
+        mh["system_type"] = "Community heating system"
+        # a complete community lodgement (heat source + fuel) so the control
+        # resolution is what's exercised, not the community strict-raise
+        mh["community_heat_source"] = "Community heating - boilers only"
+        mh["fuel"] = "Mains Gas"
+        mh["product_id"] = 0
+        mh["controls"] = (
             "Charging system linked to use of community heating, room thermostat only"
         )
         survey = from_dict(PasHubRdSapSiteNotes, raw)
@@ -1823,10 +1827,12 @@ class TestPasHubMainHeatingControlCoding:
         # A community-system control label the Group 3 lookup does not cover
         # strict-raises (naming label + system), never silently mis-rating.
         raw = load("pashub_rdsap_site_notes_example1.json")
-        raw["heating_and_hot_water"]["main_heating"][
-            "system_type"
-        ] = "Community heating system"
-        raw["heating_and_hot_water"]["main_heating"]["controls"] = "Some novel control"
+        mh = raw["heating_and_hot_water"]["main_heating"]
+        mh["system_type"] = "Community heating system"
+        mh["community_heat_source"] = "Community heating - boilers only"
+        mh["fuel"] = "Mains Gas"
+        mh["product_id"] = 0
+        mh["controls"] = "Some novel control"
         survey = from_dict(PasHubRdSapSiteNotes, raw)
 
         with pytest.raises(UnmappedPasHubLabel, match="Community heating system"):