From 6d414c7b51a18919a627c225e285e017937cf49e Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 14:18:16 +0000
Subject: [PATCH 01/12] =?UTF-8?q?Air-source=20heat-pump=20overrides=20drag?=
 =?UTF-8?q?=20the=20conservative=20Group=202=20control=20(2201)=20?=
 =?UTF-8?q?=F0=9F=9F=A5?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../epc/test_main_heating_system_overlay.py   | 25 ++++++++++++++++---
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index b42effd9b..795a9defe 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -95,17 +95,34 @@ def test_electric_room_heaters_overlay_the_room_heater_charge_control() -> None:
 def test_overlay_logs_when_it_cannot_complete_a_companion_set(
     caplog: pytest.LogCaptureFixture,
 ) -> None:
-    # An archetype the overlay cannot yet fully companion — here an air-source
-    # heat pump, whose Table 4e Group 2 conservative control is not yet mapped —
+    # An archetype the overlay cannot yet fully companion — here community
+    # heating, whose Table 4e Group 3 conservative control is not yet mapped —
     # is still overlaid (log-and-continue), but the incomplete companion set is
     # logged as an error so the known gap is visible (CloudWatch) rather than
     # silently inheriting the replaced system's stale value.
     # Act
     with caplog.at_level(logging.ERROR):
-        main_heating_overlay_for("Air source heat pump", 0)
+        main_heating_overlay_for("Community heating, boilers", 0)
 
     # Assert — the gap is reported and names the archetype.
-    assert "Air source heat pump" in caplog.text
+    assert "Community heating, boilers" in caplog.text
+
+
+def test_air_source_heat_pump_drags_the_conservative_group_2_control() -> None:
+    # The landlord names the system, not its control, so the overlay assumes
+    # the conservative Table 4e Group 2 default: 2201 ("no time or thermostatic
+    # control", +0.3 C — the largest Group 2 adjustment, so an unobserved
+    # control is never over-credited; the heat-pump mirror of storage 2401 /
+    # boiler 2101). Deliberately NOT the ASHP Measure's 2210 zone control —
+    # a measure designs a modern end-state (ADR-0024); an override describes an
+    # existing pump (ADR-0053).
+    # Act
+    simulation = main_heating_overlay_for("Air source heat pump", 0)
+
+    # Assert — SAP Table 4e Group 2 conservative heat-pump control.
+    assert simulation is not None
+    assert simulation.heating is not None
+    assert simulation.heating.main_heating_control == 2201
 
 
 def test_complete_room_heater_overlay_does_not_log_a_companion_gap(

From 6bad3a216a6a92ee2641b2685e4a3304e19a9e17 Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 14:19:20 +0000
Subject: [PATCH 02/12] =?UTF-8?q?Air-source=20heat-pump=20overrides=20drag?=
 =?UTF-8?q?=20the=20conservative=20Group=202=20control=20(2201)=20?=
 =?UTF-8?q?=F0=9F=9F=A9?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../main_heating_system_overlay.py                  | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/domain/epc/property_overlays/main_heating_system_overlay.py b/domain/epc/property_overlays/main_heating_system_overlay.py
index 2053423b9..af334f41c 100644
--- a/domain/epc/property_overlays/main_heating_system_overlay.py
+++ b/domain/epc/property_overlays/main_heating_system_overlay.py
@@ -168,6 +168,17 @@ _UNDERFLOOR_CONTROL = 2701
 # without a PCDB index (ADR-0041).
 _HEAT_PUMP_CATEGORY = 4
 _HEAT_PUMP_CODES = frozenset(range(211, 225)) | frozenset(range(521, 528))
+# SAP Table 4e Group 2 heat-pump control: 2201 ("no time or thermostatic
+# control of room temperature", +0.3 C) is the conservative default when the
+# landlord named only the system — the largest Group 2 adjustment, so an
+# unobserved control is never over-credited. Deliberately NOT the ASHP
+# Measure's 2210 zone control: a measure designs a modern end-state
+# (ADR-0024); an override describes an existing pump (ADR-0053). Scoped to the
+# WET heat pumps (211-224) — warm-air pumps (521-527) take Table 4e Group 5
+# and stay unmapped (no archetype maps to them; the incomplete-companion raise
+# guards that a future one cannot land without choosing its Group 5 control).
+_WET_HEAT_PUMP_CODES = frozenset(range(211, 225))
+_CONSERVATIVE_HEAT_PUMP_CONTROL = 2201
 
 # Community / heat-network heating (SAP Table 4a 301-304) is category 6; the
 # calculator's `_is_heat_network` keys off code OR category 6. The boiler-driven
@@ -305,6 +316,8 @@ def _control_for(code: int) -> Optional[int]:
         return _UNDERFLOOR_CONTROL
     if code in _ELECTRIC_BOILER_CODES:
         return _CONSERVATIVE_BOILER_CONTROL
+    if code in _WET_HEAT_PUMP_CODES:
+        return _CONSERVATIVE_HEAT_PUMP_CONTROL
     return None
 
 

From 950ec31d84a52717b67602bc1aab83b2d142c0f8 Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 14:19:52 +0000
Subject: [PATCH 03/12] =?UTF-8?q?Community-heating=20overrides=20drag=20th?=
 =?UTF-8?q?e=20conservative=20Group=203=20control=20(2301)=20=F0=9F=9F=A5?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../epc/test_main_heating_system_overlay.py   | 24 +++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index 795a9defe..c092c5114 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -108,6 +108,30 @@ def test_overlay_logs_when_it_cannot_complete_a_companion_set(
     assert "Community heating, boilers" in caplog.text
 
 
+@pytest.mark.parametrize(
+    "main_heating_value",
+    ["Community heating, boilers", "Community heating, CHP and boilers"],
+)
+def test_community_heating_drags_the_conservative_group_3_control(
+    main_heating_value: str,
+) -> None:
+    # The landlord names the scheme, not its control or charging arrangement.
+    # The conservative Table 4e Group 3 default is 2301 ("flat rate charging,
+    # no thermostatic control of room temperature"): the largest Group 3
+    # temperature adjustment (+0.3 C) AND the worst Table 4c(3) charging
+    # factors (space 1.10, DHW 1.05) — an unobserved control is never
+    # over-credited and an unobserved charging arrangement is never assumed
+    # usage-linked (ADR-0053). Leaving it unset inherits the replaced system's
+    # control instead (the ADR-0048 bug class).
+    # Act
+    simulation = main_heating_overlay_for(main_heating_value, 0)
+
+    # Assert — SAP Table 4e Group 3 conservative heat-network control.
+    assert simulation is not None
+    assert simulation.heating is not None
+    assert simulation.heating.main_heating_control == 2301
+
+
 def test_air_source_heat_pump_drags_the_conservative_group_2_control() -> None:
     # The landlord names the system, not its control, so the overlay assumes
     # the conservative Table 4e Group 2 default: 2201 ("no time or thermostatic

From 61f9a63b66fa2f456bb0a1a2b41d55c9451ff1ce Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 14:21:03 +0000
Subject: [PATCH 04/12] =?UTF-8?q?Community-heating=20overrides=20drag=20th?=
 =?UTF-8?q?e=20conservative=20Group=203=20control=20(2301)=20=F0=9F=9F=A9?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The last real archetype on the companion-gap log; the log test now
simulates a future incomplete archetype (warm-air heat pump, Group 5
control deliberately unmapped).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../main_heating_system_overlay.py            | 10 ++++++++++
 .../epc/test_main_heating_system_overlay.py   | 20 ++++++++++++-------
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/domain/epc/property_overlays/main_heating_system_overlay.py b/domain/epc/property_overlays/main_heating_system_overlay.py
index af334f41c..b8c945393 100644
--- a/domain/epc/property_overlays/main_heating_system_overlay.py
+++ b/domain/epc/property_overlays/main_heating_system_overlay.py
@@ -188,6 +188,14 @@ _CONSERVATIVE_HEAT_PUMP_CONTROL = 2201
 _HEAT_NETWORK_CATEGORY = 6
 _HEAT_NETWORK_CODES = frozenset({301, 302, 303, 304})
 _COMMUNITY_BOILER_CODES = frozenset({301, 302, 303})
+# SAP Table 4e Group 3 heat-network control: 2301 ("flat rate charging, no
+# thermostatic control of room temperature") is the conservative default when
+# the landlord named only the scheme. It is never-over-crediting on BOTH axes
+# the control drives: the largest Group 3 temperature adjustment (+0.3 C, tied
+# with 2302) and the worst Table 4c(3) charging factors (space 1.10, DHW 1.05
+# — an unobserved charging arrangement is never assumed usage-linked). The
+# community mirror of storage 2401 / boiler 2101 / heat-pump 2201 (ADR-0053).
+_CONSERVATIVE_HEAT_NETWORK_CONTROL = 2301
 _COMMUNITY_GAS_FUEL = 20
 
 # SAP Table 4c full boiler-control code: programmer + room thermostat + TRVs. The
@@ -318,6 +326,8 @@ def _control_for(code: int) -> Optional[int]:
         return _CONSERVATIVE_BOILER_CONTROL
     if code in _WET_HEAT_PUMP_CODES:
         return _CONSERVATIVE_HEAT_PUMP_CONTROL
+    if code in _HEAT_NETWORK_CODES:
+        return _CONSERVATIVE_HEAT_NETWORK_CONTROL
     return None
 
 
diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index c092c5114..fb856b75c 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -94,18 +94,24 @@ def test_electric_room_heaters_overlay_the_room_heater_charge_control() -> None:
 
 def test_overlay_logs_when_it_cannot_complete_a_companion_set(
     caplog: pytest.LogCaptureFixture,
+    monkeypatch: pytest.MonkeyPatch,
 ) -> None:
-    # An archetype the overlay cannot yet fully companion — here community
-    # heating, whose Table 4e Group 3 conservative control is not yet mapped —
-    # is still overlaid (log-and-continue), but the incomplete companion set is
-    # logged as an error so the known gap is visible (CloudWatch) rather than
-    # silently inheriting the replaced system's stale value.
+    # Every real archetype now resolves a complete companion set (ADR-0053),
+    # so the incomplete case is simulated: a hypothetical warm-air heat-pump
+    # archetype (SAP 521 — category 4 but its Table 4e Group 5 control is
+    # deliberately unmapped). The overlay still applies (log-and-continue),
+    # but the incomplete companion set is reported rather than silently
+    # inheriting the replaced system's stale value.
+    from domain.epc.property_overlays import main_heating_system_overlay as mod
+
+    monkeypatch.setitem(mod._MAIN_HEATING_CODES, "Warm-air heat pump", 521)
+
     # Act
     with caplog.at_level(logging.ERROR):
-        main_heating_overlay_for("Community heating, boilers", 0)
+        main_heating_overlay_for("Warm-air heat pump", 0)
 
     # Assert — the gap is reported and names the archetype.
-    assert "Community heating, boilers" in caplog.text
+    assert "Warm-air heat pump" in caplog.text
 
 
 @pytest.mark.parametrize(

From 1925cdd65d68cc03f7b505da69d81e240ae75fc1 Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 14:21:34 +0000
Subject: [PATCH 05/12] =?UTF-8?q?An=20incomplete=20heating=20companion=20s?=
 =?UTF-8?q?et=20raises=20instead=20of=20logging=20=F0=9F=9F=A5?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../epc/test_main_heating_system_overlay.py   | 23 ++++++++-----------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index fb856b75c..ec9e978aa 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -92,27 +92,24 @@ def test_electric_room_heaters_overlay_the_room_heater_charge_control() -> None:
     assert simulation.heating.main_heating_control == 2601
 
 
-def test_overlay_logs_when_it_cannot_complete_a_companion_set(
-    caplog: pytest.LogCaptureFixture,
+def test_overlay_raises_on_an_incomplete_companion_set(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None:
-    # Every real archetype now resolves a complete companion set (ADR-0053),
-    # so the incomplete case is simulated: a hypothetical warm-air heat-pump
-    # archetype (SAP 521 — category 4 but its Table 4e Group 5 control is
-    # deliberately unmapped). The overlay still applies (log-and-continue),
-    # but the incomplete companion set is reported rather than silently
-    # inheriting the replaced system's stale value.
+    # Every real archetype resolves a complete companion set, so the
+    # log-and-continue mitigation has no remaining population and the
+    # ADR-0048 end-state applies: an incomplete set FAILS LOUDLY instead of
+    # shipping a silently-incoherent cert (ADR-0053, #1444 Part C). Simulated
+    # with a hypothetical warm-air heat-pump archetype (SAP 521 — category 4
+    # but its Table 4e Group 5 control is deliberately unmapped): a future
+    # archetype cannot land without choosing its companions.
     from domain.epc.property_overlays import main_heating_system_overlay as mod
 
     monkeypatch.setitem(mod._MAIN_HEATING_CODES, "Warm-air heat pump", 521)
 
-    # Act
-    with caplog.at_level(logging.ERROR):
+    # Act / Assert — the raise names the archetype.
+    with pytest.raises(ValueError, match="Warm-air heat pump"):
         main_heating_overlay_for("Warm-air heat pump", 0)
 
-    # Assert — the gap is reported and names the archetype.
-    assert "Warm-air heat pump" in caplog.text
-
 
 @pytest.mark.parametrize(
     "main_heating_value",

From 6707ab084fd1c38371a052e38b5bae1da39abb7c Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 14:22:40 +0000
Subject: [PATCH 06/12] =?UTF-8?q?An=20incomplete=20heating=20companion=20s?=
 =?UTF-8?q?et=20raises=20instead=20of=20logging=20=F0=9F=9F=A9?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

ADR-0048's intended end-state (#1444 Part C): every mapped archetype now
resolves confident companions, so an incomplete set can only mean a new
archetype landed without choosing them — fail loudly at overlay time.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../main_heating_system_overlay.py            | 29 ++++++++-----------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/domain/epc/property_overlays/main_heating_system_overlay.py b/domain/epc/property_overlays/main_heating_system_overlay.py
index b8c945393..6d25d979c 100644
--- a/domain/epc/property_overlays/main_heating_system_overlay.py
+++ b/domain/epc/property_overlays/main_heating_system_overlay.py
@@ -28,7 +28,6 @@ are left UNKNOWN until modelled. Unresolvable values produce no overlay.
 
 from __future__ import annotations
 
-import logging
 from typing import Optional
 
 from domain.modelling.simulation import EpcSimulation, HeatingOverlay
@@ -36,8 +35,6 @@ from domain.sap10_calculator.tables.table_12a import (
     OFF_PEAK_IMPLYING_HEATING_CODES,
 )
 
-logger = logging.getLogger(__name__)
-
 # Off-peak (Economy 7) meter. Electric storage / CPSU systems charge overnight at
 # the low rate and cannot run economically on a single-rate meter; "Dual" lets
 # the §12 dispatch resolve the specific tariff (storage 7-hour, CPSU 10-hour).
@@ -418,21 +415,19 @@ def main_heating_overlay_for(
     category = _category_for(code)
     control = _control_for(code)
     if category is None or control is None:
-        # A system-replacing override should stamp a complete, coherent companion
+        # A system-replacing override must stamp a complete, coherent companion
         # set; an unmapped category or control leaves the field unset, so the
-        # effective cert inherits the REPLACED system's value (a silent mis-rating
-        # — e.g. a room heater keeping a storage heater's category/control). We do
-        # not yet have confident defaults for every archetype, so log-and-continue
-        # (matching `flag_fuel_mismatch`) to make the gap visible for review
-        # rather than raise mid-run.
-        logger.error(
-            "Landlord main_heating_system %r (SAP code %d) overlaid with an "
-            "incomplete companion set (category=%s, control=%s); the effective "
-            "cert may inherit the replaced system's value — known gap, review",
-            main_heating_value,
-            code,
-            category,
-            control,
+        # effective cert inherits the REPLACED system's value — the silent
+        # mis-rating class ADR-0048 exists to stop. Every mapped archetype now
+        # carries confident defaults (ADR-0050/0052/0053), so an incomplete set
+        # can only mean a new archetype landed without choosing its companions:
+        # fail loudly at overlay time rather than ship an incoherent cert
+        # (ADR-0048's intended end-state, #1444 Part C).
+        raise ValueError(
+            f"Landlord main_heating_system {main_heating_value!r} (SAP code "
+            f"{code}) resolves an incomplete companion set (category="
+            f"{category}, control={control}); add the archetype's SAP Table 4a "
+            f"category and conservative Table 4e control before mapping it"
         )
     return EpcSimulation(
         heating=HeatingOverlay(

From 77110f22604f3009075ad61e052b0e50bfe770c4 Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 14:23:44 +0000
Subject: [PATCH 07/12] =?UTF-8?q?Record=20ADR-0053:=20companion=20taxonomy?=
 =?UTF-8?q?=20complete,=20incomplete=20set=20raises=20=F0=9F=9F=AA?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 ...taxonomy-complete-incomplete-set-raises.md | 89 +++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 docs/adr/0053-heating-override-companion-taxonomy-complete-incomplete-set-raises.md

diff --git a/docs/adr/0053-heating-override-companion-taxonomy-complete-incomplete-set-raises.md b/docs/adr/0053-heating-override-companion-taxonomy-complete-incomplete-set-raises.md
new file mode 100644
index 000000000..152e19224
--- /dev/null
+++ b/docs/adr/0053-heating-override-companion-taxonomy-complete-incomplete-set-raises.md
@@ -0,0 +1,89 @@
+# The heating-override companion taxonomy is complete; an incomplete set now raises
+
+## Status
+
+accepted
+
+## Context
+
+[ADR-0048](0048-heating-override-forces-category-and-control-defers-fuel-and-meter.md)
+set the invariant — a system-replacing heating override emits a complete
+category + control companion set, never inheriting the replaced system's — and
+intended, once the taxonomy was covered, to "flip the log to a raise, so the
+coherence invariant is enforced" (#1444 Part C).
+[ADR-0050](0050-electric-underfloor-override-drags-category-8-and-conservative-group-7-control.md)
+(underfloor) and
+[ADR-0052](0052-electric-boiler-and-cpsu-overrides-drag-category-2-and-conservative-group-1-control.md)
+(electric boilers) filled two families. Two archetype families remained on the
+gap-log, and with them Part C stayed blocked:
+
+- **"Air source heat pump" (SAP 211)** — category 4 already forced, control
+  `None` (Table 4e Group 2 unmapped). No live overrides today (census across
+  all portfolios: 0), so this is taxonomy completion, not a live defect.
+- **"Community heating, boilers" / "…, CHP and boilers" (301/302)** — category
+  6 already forced, control `None` (Group 3 unmapped). **2,220 live
+  overrides** — the largest population on the log. The inherited control is
+  doubly load-bearing for heat networks: it feeds the Table 4e temperature
+  adjustment *and* the SAP 10.2 Table 4c(3) charging factors (worksheet
+  (305)/(305a)).
+
+## Decision
+
+1. **Wet heat pumps (Table 4a 211-224) drag control 2201** — Table 4e Group 2
+   "no time or thermostatic control of room temperature", **+0.3 °C**, the
+   largest Group 2 adjustment: the conservative in-group default (the heat-pump
+   mirror of storage 2401 / room-heater 2601 / underfloor 2701 / boiler 2101).
+   Warm-air heat pumps (521-527) are deliberately left unmapped — no archetype
+   reaches them, and the raise below is the guard that a future warm-air
+   archetype cannot land without choosing its Group 5 control.
+
+   This is the *existing-system* fill policy: the ASHP **Measure** overlay
+   installs 2210 (time-and-temperature zone control) because a measure designs
+   a modern end-state (ADR-0024); a landlord override describes an existing
+   pump whose control was never observed, so the conservative default applies.
+
+2. **Community heating (301/302) drags control 2301** — Table 4e Group 3
+   "flat rate charging, no thermostatic control of room temperature". It is
+   the never-over-crediting default on **both** axes the control drives: the
+   largest Group 3 temperature adjustment (**+0.3 °C**, tied with 2302) and
+   the worst Table 4c(3) charging factors (space **1.10**, DHW **1.05** — an
+   unobserved charging arrangement is never assumed to be usage-linked).
+   As with every forced companion (ADR-0035/0048 pattern), this overwrites a
+   better control lodged for the replaced system: the override asserts the
+   system afresh and synthesis owns coherence.
+
+3. **An incomplete companion set now raises** (`ValueError`) instead of
+   logging. Every archetype in `_MAIN_HEATING_CODES` resolves a complete
+   category + control (gas boilers via their dedicated overlay; all others via
+   `_category_for`/`_control_for`), so the log-and-continue mitigation has no
+   remaining population — and a silent log was only ever a stop-gap
+   (ADR-0048: "the intended end-state is to fill each archetype's
+   category/control … and then flip the log to a raise"). A future archetype
+   added without companions now fails loudly at overlay time rather than
+   shipping a silently-incoherent cert.
+
+## Consequences
+
+- The companion-gap error log is gone; #1444 closes.
+- Community overrides re-model against the conservative 2301: dwellings whose
+  replaced-system control was inherited converge on one defensible assumption.
+  Live sample (portfolio 796, 12 properties): baseline shifts of **0 to −3
+  SAP** (typically −1 to −2). The inherited controls were unobserved
+  usage-linked credits (2306/2307/2309) or outright group-incoherent — two
+  dwellings carried a Group-1 *boiler* zone control (2110) on a heat network —
+  so the shift removes credit that was never evidenced.
+- Adding a heating archetype now *requires* choosing its category + control
+  (or extending the family sets) — the raise turns the ADR-0048 checklist into
+  an enforced contract.
+
+### Alternatives rejected
+
+- **A zero-adjustment / usage-linked community default (2307+).** Rejected:
+  credits a charging arrangement and thermostat the landlord never reported;
+  the conservative default is the established pattern.
+- **Keep log-and-continue indefinitely.** Rejected: the log was the interim
+  mitigation while the taxonomy was incomplete; leaving it means the next
+  archetype ships the ADR-0048 inheritance bug silently again.
+- **Raise on warm-air heat-pump codes' missing control now.** Not applicable —
+  no archetype maps to 521-527; the raise fires exactly when one is added
+  without its Group 5 control, which is the point.

From 2bfda711d8cc84024cbecbef97e09aa21907107b Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 16:32:15 +0000
Subject: [PATCH 08/12] =?UTF-8?q?Community-heating=20overrides=20default?=
 =?UTF-8?q?=20to=20Group=203=20control=202313=20=F0=9F=9F=A5?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../epc/test_main_heating_system_overlay.py   | 22 ++++++++++---------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index ec9e978aa..576b8716d 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -115,24 +115,26 @@ def test_overlay_raises_on_an_incomplete_companion_set(
     "main_heating_value",
     ["Community heating, boilers", "Community heating, CHP and boilers"],
 )
-def test_community_heating_drags_the_conservative_group_3_control(
+def test_community_heating_drags_the_default_group_3_control(
     main_heating_value: str,
 ) -> None:
     # The landlord names the scheme, not its control or charging arrangement.
-    # The conservative Table 4e Group 3 default is 2301 ("flat rate charging,
-    # no thermostatic control of room temperature"): the largest Group 3
-    # temperature adjustment (+0.3 C) AND the worst Table 4c(3) charging
-    # factors (space 1.10, DHW 1.05) — an unobserved control is never
-    # over-credited and an unobserved charging arrangement is never assumed
-    # usage-linked (ADR-0053). Leaving it unset inherits the replaced system's
-    # control instead (the ADR-0048 bug class).
+    # The Table 4e Group 3 default is 2313 ("flat rate charging, room
+    # thermostat and TRVs"): community schemes skew modern and the portfolio's
+    # own lodged community certs are overwhelmingly thermostatted (modal 2306;
+    # none lodge 2301), so the KIT axis concedes to the evidence — while the
+    # CHARGING axis stays flat-rate (space 1.05 / DHW 1.05): the billing
+    # arrangement is scheme paperwork an override genuinely cannot see, so
+    # usage-linked (1.0/1.0) is never assumed (ADR-0053, decided with Khalim).
+    # Leaving the control unset inherits the replaced system's instead (the
+    # ADR-0048 bug class).
     # Act
     simulation = main_heating_overlay_for(main_heating_value, 0)
 
-    # Assert — SAP Table 4e Group 3 conservative heat-network control.
+    # Assert — SAP Table 4e Group 3 default heat-network control.
     assert simulation is not None
     assert simulation.heating is not None
-    assert simulation.heating.main_heating_control == 2301
+    assert simulation.heating.main_heating_control == 2313
 
 
 def test_air_source_heat_pump_drags_the_conservative_group_2_control() -> None:

From 72ccc920c5d8a5a56355b20407bfc90ca6743ba7 Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 16:32:58 +0000
Subject: [PATCH 09/12] =?UTF-8?q?Community-heating=20overrides=20default?=
 =?UTF-8?q?=20to=20Group=203=20control=202313=20=F0=9F=9F=A9?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Per-axis choice (decided with Khalim): the kit axis concedes to the
evidence (community schemes skew modern; lodged community certs are
overwhelmingly thermostatted, none lodge 2301), the charging axis stays
flat-rate — usage-linked billing is scheme paperwork an override
cannot see.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../main_heating_system_overlay.py            | 22 +++++++++++--------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/domain/epc/property_overlays/main_heating_system_overlay.py b/domain/epc/property_overlays/main_heating_system_overlay.py
index 6d25d979c..243326cfd 100644
--- a/domain/epc/property_overlays/main_heating_system_overlay.py
+++ b/domain/epc/property_overlays/main_heating_system_overlay.py
@@ -185,14 +185,18 @@ _CONSERVATIVE_HEAT_PUMP_CONTROL = 2201
 _HEAT_NETWORK_CATEGORY = 6
 _HEAT_NETWORK_CODES = frozenset({301, 302, 303, 304})
 _COMMUNITY_BOILER_CODES = frozenset({301, 302, 303})
-# SAP Table 4e Group 3 heat-network control: 2301 ("flat rate charging, no
-# thermostatic control of room temperature") is the conservative default when
-# the landlord named only the scheme. It is never-over-crediting on BOTH axes
-# the control drives: the largest Group 3 temperature adjustment (+0.3 C, tied
-# with 2302) and the worst Table 4c(3) charging factors (space 1.10, DHW 1.05
-# — an unobserved charging arrangement is never assumed usage-linked). The
-# community mirror of storage 2401 / boiler 2101 / heat-pump 2201 (ADR-0053).
-_CONSERVATIVE_HEAT_NETWORK_CONTROL = 2301
+# SAP Table 4e Group 3 heat-network control: 2313 ("flat rate charging, room
+# thermostat and TRVs") is the default when the landlord named only the scheme
+# — a per-axis choice (ADR-0053, decided with Khalim). KIT axis: community
+# schemes skew modern and the portfolio's lodged community certs are
+# overwhelmingly thermostatted (modal 2306; none lodge 2301), so a room
+# thermostat + TRVs is the evidence-backed assumption (temperature adjustment
+# 0.0). CHARGING axis: flat rate (Table 4c(3) space 1.05 / DHW 1.05) — the
+# billing arrangement is scheme paperwork an override cannot see, so the
+# usage-linked credit (1.0/1.0) is never assumed. An assessor-OBSERVED Group 3
+# control on the cert is kept in preference to this default (the overlay sets
+# `keep_existing_heat_network_control`; the applicator honours it).
+_DEFAULT_HEAT_NETWORK_CONTROL = 2313
 _COMMUNITY_GAS_FUEL = 20
 
 # SAP Table 4c full boiler-control code: programmer + room thermostat + TRVs. The
@@ -324,7 +328,7 @@ def _control_for(code: int) -> Optional[int]:
     if code in _WET_HEAT_PUMP_CODES:
         return _CONSERVATIVE_HEAT_PUMP_CONTROL
     if code in _HEAT_NETWORK_CODES:
-        return _CONSERVATIVE_HEAT_NETWORK_CONTROL
+        return _DEFAULT_HEAT_NETWORK_CONTROL
     return None
 
 

From 04810896e06d39c407fe80b9fd43a1edd7c679ee Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 16:33:40 +0000
Subject: [PATCH 10/12] =?UTF-8?q?A=20community=20override=20keeps=20an=20a?=
 =?UTF-8?q?ssessor-observed=20Group=203=20control=20=F0=9F=9F=A5?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../epc/test_main_heating_system_overlay.py   | 45 +++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index 576b8716d..dc50dd2d5 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -647,6 +647,51 @@ def test_unresolvable_or_unmodelled_heating_produces_no_overlay(
     assert simulation is None
 
 
+def test_community_override_keeps_an_observed_group_3_control() -> None:
+    # A community override on a cert that ALREADY lodges community heating is a
+    # confirmation, not a system switch — the assessor observed the control
+    # (e.g. 2306, "charging linked to use, programmer and TRVs", worth ~1-2 SAP
+    # over the flat-rate default). Stamping the 2313 default over it would
+    # destroy real information, so the overlay opts into keeping an existing
+    # Table 4e GROUP 3 control (the heat-network mirror of
+    # `keep_existing_off_peak_meter`, ADR-0053).
+    # Arrange — a cert lodging community heating with an observed 2306.
+    baseline = build_epc()
+    main = baseline.sap_heating.main_heating_details[0]
+    main.sap_main_heating_code = 301
+    main.main_heating_category = 6
+    main.main_heating_control = 2306
+    overlay = main_heating_overlay_for("Community heating, boilers", 0)
+    assert overlay is not None
+
+    # Act
+    result = apply_simulations(baseline, [overlay])
+
+    # Assert — the observed usage-linked control survives.
+    assert result.sap_heating.main_heating_details[0].main_heating_control == 2306
+
+
+def test_community_override_replaces_a_cross_family_control() -> None:
+    # When the replaced system was a DIFFERENT family, its control is stale by
+    # definition — a Group-1 boiler zone control (2110) has no meaning on a
+    # heat network (two live portfolio-796 dwellings carried exactly that) —
+    # so the Group 3 default is stamped (ADR-0053).
+    # Arrange — a cert lodging a gas boiler with zone control.
+    baseline = build_epc()
+    main = baseline.sap_heating.main_heating_details[0]
+    main.sap_main_heating_code = 102
+    main.main_heating_category = 2
+    main.main_heating_control = 2110
+    overlay = main_heating_overlay_for("Community heating, boilers", 0)
+    assert overlay is not None
+
+    # Act
+    result = apply_simulations(baseline, [overlay])
+
+    # Assert — the stale boiler control is replaced by the Group 3 default.
+    assert result.sap_heating.main_heating_details[0].main_heating_control == 2313
+
+
 def test_main_heating_override_remaps_the_primary_system_code() -> None:
     # Arrange
     baseline = build_epc()

From 9153fa2523a5887b36ab5868d5c454d024b12f1f Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 16:35:08 +0000
Subject: [PATCH 11/12] =?UTF-8?q?A=20community=20override=20keeps=20an=20a?=
 =?UTF-8?q?ssessor-observed=20Group=203=20control=20=F0=9F=9F=A9?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The heat-network mirror of keep_existing_off_peak_meter: the override's
2313 default applies only when the replaced system's control is
cross-family (stale); an observed community control survives.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../main_heating_system_overlay.py            |  5 ++++
 .../modelling/scoring/overlay_applicator.py   | 24 +++++++++++++++++--
 domain/modelling/simulation.py                |  9 +++++++
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/domain/epc/property_overlays/main_heating_system_overlay.py b/domain/epc/property_overlays/main_heating_system_overlay.py
index 243326cfd..946c648ca 100644
--- a/domain/epc/property_overlays/main_heating_system_overlay.py
+++ b/domain/epc/property_overlays/main_heating_system_overlay.py
@@ -445,5 +445,10 @@ def main_heating_overlay_for(
             # (e.g. a 24-hour all-low tariff). Measures, which re-meter for real,
             # build their HeatingOverlay directly and leave this False.
             keep_existing_off_peak_meter=True,
+            # Likewise a heat-network override's control default (2313) must
+            # not overwrite an assessor-OBSERVED Group 3 control on a community
+            # cert being confirmed — only a stale cross-family control is
+            # replaced (ADR-0053).
+            keep_existing_heat_network_control=code in _HEAT_NETWORK_CODES,
         )
     )
diff --git a/domain/modelling/scoring/overlay_applicator.py b/domain/modelling/scoring/overlay_applicator.py
index 216463dab..1a9357033 100644
--- a/domain/modelling/scoring/overlay_applicator.py
+++ b/domain/modelling/scoring/overlay_applicator.py
@@ -152,6 +152,13 @@ _SAP_HEATING_FIELDS: tuple[str, ...] = (
 _ENERGY_SOURCE_FIELDS: tuple[str, ...] = ("meter_type", "gas_connection_available")
 
 
+def _is_heat_network_control(control: object) -> bool:
+    """True iff the lodged control is a SAP Table 4e Group 3 (heat network)
+    code — 2301-2314 — i.e. an assessor-observed community control a
+    heat-network override's default must not overwrite (ADR-0053)."""
+    return isinstance(control, int) and 2301 <= control <= 2314
+
+
 def _is_off_peak_meter(meter_type: object) -> bool:
     """True iff the meter resolves to an off-peak Table 12a tariff (not the
     STANDARD single-rate column). Unparseable / absent meters count as not
@@ -177,8 +184,21 @@ def _fold_heating(epc: EpcPropertyData, overlay: HeatingOverlay) -> None:
     main = epc.sap_heating.main_heating_details[0]
     for field_name in _MAIN_HEATING_FIELDS:
         value = getattr(overlay, field_name)
-        if value is not None:
-            setattr(main, field_name, value)
+        if value is None:
+            continue
+        # A community override's control is a coherent default, not an observed
+        # one: when it opts in (`keep_existing_heat_network_control`) and the
+        # cert already lodges a Table 4e GROUP 3 control (assessor-observed on
+        # a community cert being confirmed), keep the cert's. A cross-family
+        # control (boiler 2110, storage 2401) is stale and is still replaced
+        # (ADR-0053).
+        if (
+            field_name == "main_heating_control"
+            and overlay.keep_existing_heat_network_control
+            and _is_heat_network_control(main.main_heating_control)
+        ):
+            continue
+        setattr(main, field_name, value)
     # `main_heating_index_number` (PCDB-resolved, e.g. a heat pump) and
     # `sap_main_heating_code` (Table 4a-resolved, e.g. storage heaters) are
     # mutually-exclusive efficiency anchors: a whole-system replacement to one
diff --git a/domain/modelling/simulation.py b/domain/modelling/simulation.py
index 79855940e..55c52855e 100644
--- a/domain/modelling/simulation.py
+++ b/domain/modelling/simulation.py
@@ -200,6 +200,15 @@ class HeatingOverlay:
     # MEASURE re-meters for real (Elmhurst re-lodges 18-hour → Dual on a storage
     # install), so it leaves this False. `_fold_heating` reads it.
     keep_existing_off_peak_meter: bool = False
+    # The community-heating mirror of the flag above (ADR-0053): a heat-network
+    # override's `main_heating_control` is a coherent DEFAULT, not an observed
+    # control — when the cert already lodges a Table 4e Group 3 control the
+    # assessor observed it (a community cert being confirmed, not replaced), so
+    # the default must not overwrite it (e.g. a usage-linked 2306 downgraded to
+    # flat-rate 2313 destroys ~1-2 real SAP). A cross-family control (a boiler
+    # 2110, storage 2401) is stale by definition and is still replaced.
+    # `_fold_heating` reads it.
+    keep_existing_heat_network_control: bool = False
 
 
 @dataclass(frozen=True)

From 1bcb55784a811d1dc44fb0d8e93e4f89dff4cc6b Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Fri, 3 Jul 2026 16:37:20 +0000
Subject: [PATCH 12/12] =?UTF-8?q?Amend=20ADR-0053:=20community=20default?=
 =?UTF-8?q?=202313=20with=20keep-observed=20Group=203=20controls=20?=
 =?UTF-8?q?=F0=9F=9F=AA?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 ...taxonomy-complete-incomplete-set-raises.md | 58 +++++++++++++------
 1 file changed, 39 insertions(+), 19 deletions(-)

diff --git a/docs/adr/0053-heating-override-companion-taxonomy-complete-incomplete-set-raises.md b/docs/adr/0053-heating-override-companion-taxonomy-complete-incomplete-set-raises.md
index 152e19224..0f1ca0cd7 100644
--- a/docs/adr/0053-heating-override-companion-taxonomy-complete-incomplete-set-raises.md
+++ b/docs/adr/0053-heating-override-companion-taxonomy-complete-incomplete-set-raises.md
@@ -42,15 +42,27 @@ gap-log, and with them Part C stayed blocked:
    a modern end-state (ADR-0024); a landlord override describes an existing
    pump whose control was never observed, so the conservative default applies.
 
-2. **Community heating (301/302) drags control 2301** — Table 4e Group 3
-   "flat rate charging, no thermostatic control of room temperature". It is
-   the never-over-crediting default on **both** axes the control drives: the
-   largest Group 3 temperature adjustment (**+0.3 °C**, tied with 2302) and
-   the worst Table 4c(3) charging factors (space **1.10**, DHW **1.05** — an
-   unobserved charging arrangement is never assumed to be usage-linked).
-   As with every forced companion (ADR-0035/0048 pattern), this overwrites a
-   better control lodged for the replaced system: the override asserts the
-   system afresh and synthesis owns coherence.
+2. **Community heating (301/302) defaults to control 2313, keeping an
+   assessor-observed Group 3 control** (decided with Khalim, revising the
+   first-cut 2301). The control encodes two independent unknowns and the
+   default is chosen per axis:
+   - **Kit axis** (thermostat/TRVs): community schemes skew modern, and the
+     portfolio's own lodged community certs are overwhelmingly thermostatted
+     (modal control 2306; none lodge 2301) — so 2313 ("flat rate charging,
+     room thermostat and TRVs", temperature adjustment 0.0) concedes this
+     axis to the evidence.
+   - **Charging axis** (flat rate vs usage-linked): the billing arrangement
+     is scheme paperwork an override genuinely cannot see, so flat rate
+     (Table 4c(3) space **1.05**, DHW **1.05**) is retained — the
+     usage-linked credit (1.0/1.0) is never assumed.
+   - **Keep-observed**: when the cert already lodges a Group 3 control the
+     override is confirming a community system, not replacing one — the
+     assessor observed that control, and stamping any default over it
+     destroys real information (a usage-linked 2306 is worth ~1-2 SAP over
+     flat-rate). The overlay opts in via
+     `keep_existing_heat_network_control` (the control mirror of ADR-0035's
+     `keep_existing_off_peak_meter`); only a stale cross-family control (the
+     boiler-2110 / storage-2401 inheritances) is replaced by 2313.
 
 3. **An incomplete companion set now raises** (`ValueError`) instead of
    logging. Every archetype in `_MAIN_HEATING_CODES` resolves a complete
@@ -65,22 +77,30 @@ gap-log, and with them Part C stayed blocked:
 ## Consequences
 
 - The companion-gap error log is gone; #1444 closes.
-- Community overrides re-model against the conservative 2301: dwellings whose
-  replaced-system control was inherited converge on one defensible assumption.
-  Live sample (portfolio 796, 12 properties): baseline shifts of **0 to −3
-  SAP** (typically −1 to −2). The inherited controls were unobserved
-  usage-linked credits (2306/2307/2309) or outright group-incoherent — two
-  dwellings carried a Group-1 *boiler* zone control (2110) on a heat network —
-  so the shift removes credit that was never evidenced.
+- Community overrides converge on defensible controls with minimal score
+  churn. Live sample (portfolio 796, 12 properties): the ten dwellings with
+  assessor-observed Group 3 controls (2306/2307/2309) shift **±0.0** — their
+  observed controls survive the override — and only the two group-incoherent
+  dwellings (a Group-1 *boiler* zone control 2110 riding on a heat network)
+  move, **−1.0** each onto the 2313 default. Contrast the first-cut 2301
+  design, which shifted the whole sample 0 to −3.
 - Adding a heating archetype now *requires* choosing its category + control
   (or extending the family sets) — the raise turns the ADR-0048 checklist into
   an enforced contract.
 
 ### Alternatives rejected
 
-- **A zero-adjustment / usage-linked community default (2307+).** Rejected:
-  credits a charging arrangement and thermostat the landlord never reported;
-  the conservative default is the established pattern.
+- **The maximally conservative community default (2301).** The first cut.
+  Rejected on evidence: no lodged community cert in the portfolio carries
+  2301, so it under-rates the typical (modern, thermostatted) scheme and
+  shifted the sampled cohort 0 to −3 SAP for no informational gain.
+- **A usage-linked community default (2306/2312/2314).** Rejected: credits a
+  billing arrangement the landlord never reported — the charging axis is the
+  one the override genuinely cannot observe, so it stays flat-rate.
+- **Stamping the default over an observed Group 3 control.** Rejected: the
+  ADR-0035 "always stamp" pattern exists to kill *stale* companions; an
+  in-group control on a confirmed community cert is observed data, and
+  overwriting it is information destruction, not coherence.
 - **Keep log-and-continue indefinitely.** Rejected: the log was the interim
   mitigation while the taxonomy was incomplete; leaving it means the next
   archetype ships the ADR-0048 inheritance bug silently again.