Slice 21a: relabel ambient SAP 10.3 → SAP 10.2 in calculator docstrings

The codebase targets SAP 10.2 (14-03-2025) per ADR-0010 and the values
match SAP 10.2 (grid CO2 = 0.136 not 0.086, ECF deflator = 0.42, etc.).
But ~35 docstrings/comments labelled formulas / sections / appendices
as "SAP 10.3 (13-01-2026)" — mis-labeling without affecting behaviour.

Relabels all of them to "SAP 10.2 specification (14-03-2025)" where the
formula being implemented is identical between 10.2 and 10.3 (which is
the vast majority — §1-§9 heat balance, §11/§13 SAP rating equations,
Appendix U climate tables, Table 9a/9c utilisation factor).

Intentionally retained:
- `worksheet/rating.py:14` — explicit comparison "SAP 10.3 widens these
  to 0.36 / 16.21 / 108.8 / 120.5" annotating where 10.3 values would
  differ from the 10.2 values we ship.
- `tables/table_12.py` — its docstring explicitly compares 10.2 vs 10.3
  CO2 / PEF differences; the file's purpose is the 10.2 → 10.3 reference
  table, so the 10.3 label is intentional discussion.

All 515 passing tests continue to pass (only the 48 known cascade-pin
failures from slice 19a remain — those are real residuals, not label
issues).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

packages/domain/src/domain/sap/calculator.py

@@ -1,4 +1,4 @@
-"""SAP 10.3 synthetic-input calculator orchestrator.
+"""SAP 10.2 synthetic-input calculator orchestrator.
 
 Drives the 12-month heat-balance loop from a typed `CalculatorInputs`
 aggregate and emits a typed `SapResult`. This module is the physics
@@ -26,7 +26,7 @@ Annual totals = month sums; ECF = §13 Table 12 deflator × total cost /
 emission factor × delivered fuel (single-fuel approximation in this
 slice — slice S-A8 splits hot-water/lighting onto per-fuel factors).
 
-Reference: SAP 10.3 specification (13-01-2026) §§5-13 (pages 23-43), Table
+Reference: SAP 10.2 specification (14-03-2025) §§5-13 (pages 23-43), Table
 9a/9b/9c (pages 184-186), Table 12 (page 191), Appendix L + U.
 """
 
@@ -120,7 +120,7 @@ _ZERO_FUEL_COST_RESULT: Final[FuelCostResult] = FuelCostResult(
 
 @dataclass(frozen=True)
 class CalculatorInputs:
-    """Synthetic SAP 10.3 calculator inputs. The cert→inputs mapper
+    """Synthetic SAP 10.2 calculator inputs. The cert→inputs mapper
     (S-A7b) produces one of these from an `EpcPropertyData`.
 
     Fuel-cost fields are per-end-use because SAP §12 / Table 32 charges
@@ -224,7 +224,7 @@ class CalculatorInputs:
 
 @dataclass(frozen=True)
 class MonthlyEntry:
-    """Per-month worksheet outputs for downstream audit. SAP 10.3 §§5-9."""
+    """Per-month worksheet outputs for downstream audit. SAP 10.2 §§5-9."""
 
     month: int
     external_temp_c: float
@@ -321,7 +321,7 @@ def _solve_month(
 
 
 def calculate_sap_from_inputs(inputs: CalculatorInputs) -> SapResult:
-    """Run SAP 10.3 §§5-13 monthly loop on synthetic inputs; return a
+    """Run SAP 10.2 §§5-13 monthly loop on synthetic inputs; return a
     typed `SapResult`. Cert-shape mapping is the job of `cert_to_inputs`
     (S-A7b); this entry point is pure physics."""
     tfa = inputs.dimensions.total_floor_area_m2
@@ -521,7 +521,7 @@ def calculate_sap_from_inputs(inputs: CalculatorInputs) -> SapResult:
 
 
 class Sap10Calculator:
-    """Deterministic SAP 10.3 calculator entry point. Maps an
+    """Deterministic SAP 10.2 calculator entry point. Maps an
     `EpcPropertyData` to typed `CalculatorInputs` via the RdSAP-driven
     `cert_to_inputs` mapper and runs the 12-month worksheet loop.
 

packages/domain/src/domain/sap/climate/appendix_u.py

@@ -1,7 +1,7 @@
-"""SAP 10.3 Appendix U — climate data lookups.
+"""SAP 10.2 Appendix U — climate data lookups.
 
 Source: BRE, *The Government's Standard Assessment Procedure for Energy
-Rating of Dwellings, SAP 10.3* (13-01-2026), Appendix U.
+Rating of Dwellings, SAP 10.2* (14-03-2025), Appendix U.
 
 Three monthly tables across 22 SAP climate regions (index 0 = UK average,
 1-21 = named regions per Table U6 postcode mapping):
@@ -11,7 +11,7 @@ Three monthly tables across 22 SAP climate regions (index 0 = UK average,
 - Table U3: Mean global solar irradiance on a horizontal plane (W/m²)
   plus monthly solar declination (°)
 
-Month is 1-12 (January = 1). Region indices map to the SAP 10.3 region
+Month is 1-12 (January = 1). Region indices map to the SAP 10.2 region
 names; lookup helpers raise `ValueError` on out-of-range inputs so callers
 can fail fast.
 """
@@ -109,7 +109,7 @@ def wind_speed_m_per_s(region: int, month: int) -> float:
 # Table U3 — Mean global solar irradiance on a horizontal plane (W/m²),
 # 22 regions × 12 months. Used (with Table U3 declination + per-window
 # orientation/pitch) to derive surface flux for solar-gains calculation
-# (SAP 10.3 §6.1).
+# (SAP 10.2 §6.1).
 _TABLE_U3: Final[tuple[tuple[float, ...], ...]] = (
     (26, 54, 96, 150, 192, 200, 189, 157, 115, 66, 33, 21),    # 0 UK average
     (30, 56, 98, 157, 195, 217, 203, 173, 127, 73, 39, 24),    # 1 Thames
@@ -139,7 +139,7 @@ _TABLE_U3: Final[tuple[tuple[float, ...], ...]] = (
 def horizontal_solar_irradiance_w_per_m2(region: int, month: int) -> float:
     """Mean global solar irradiance on a horizontal plane (W/m²) for a SAP
     climate region in a month. The starting point for the per-orientation
-    surface-flux calculation in SAP 10.3 §6.1."""
+    surface-flux calculation in SAP 10.2 §6.1."""
     _validate(region, month)
     return float(_TABLE_U3[region][month - 1])
 
@@ -153,7 +153,7 @@ _SOLAR_DECLINATION: Final[tuple[float, ...]] = (
 
 
 def solar_declination_deg(month: int) -> float:
-    """Solar declination angle (°) for the given month. SAP 10.3 Appendix U
+    """Solar declination angle (°) for the given month. SAP 10.2 Appendix U
     Table U3 footer — independent of region."""
     _validate_month(month)
     return _SOLAR_DECLINATION[month - 1]

packages/domain/src/domain/sap/rdsap/cert_to_inputs.py

@@ -1,4 +1,4 @@
-"""RdSAP 10 cert → SAP 10.3 CalculatorInputs mapping.
+"""RdSAP 10 cert → SAP 10.2 CalculatorInputs mapping.
 
 Reads `EpcPropertyData` (the gov EPC API / site-notes domain model) and
 produces the typed `CalculatorInputs` the synthetic-input orchestrator
@@ -13,7 +13,7 @@ Defaulting rules per RdSAP 10 (10-06-2025):
   - Heat transmission: §5 (port in `worksheet/heat_transmission.py`)
   - Infiltration:      §4 Table 5 (port in `worksheet/ventilation.py`)
   - Living-area fraction: Table 27 by `habitable_rooms_count`
-  - Heating efficiency: SAP 10.3 Tables 4a/4b (existing
+  - Heating efficiency: SAP 10.2 Tables 4a/4b (existing
     `domain.ml.sap_efficiencies.seasonal_efficiency` cascade)
   - Hot-water demand: Appendix J (existing `domain.ml.demand`)
   - Lighting demand: Appendix L simplified (`domain.ml.demand`)
@@ -30,7 +30,7 @@ Edge cases deliberately deferred to Session B:
 - control_temperature_adjustment from main_heating_control code 2101/2103/2106
   (defaults to 0)
 
-Reference: RdSAP 10 specification (10-06-2025); SAP 10.3 specification
+Reference: RdSAP 10 specification (10-06-2025); SAP 10.2 specification
 (13-01-2026) Tables 4a/4b/4e/12.
 """
 
@@ -277,7 +277,7 @@ SAP_10_2_SPEC_PRICES: Final[PriceTable] = PriceTable(
 )
 
 
-# SAP 10.3 Table 9 main_heating_control codes → control type (1/2/3).
+# SAP 10.2 Table 9 main_heating_control codes → control type (1/2/3).
 # Type 1: no time + temp control, or one but not both.
 # Type 2: programmer + room thermostat (+/− TRVs).
 # Type 3: time-and-temperature zone control (e.g. separate living-zone
@@ -376,7 +376,7 @@ def _first_main_heating(epc: EpcPropertyData) -> Optional[MainHeatingDetail]:
 
 
 def _control_type(main: Optional[MainHeatingDetail]) -> int:
-    """SAP 10.3 §7.1 / Table 9 control type 1/2/3 from the
+    """SAP 10.2 §7.1 / Table 9 control type 1/2/3 from the
     `main_heating_control` code on `MainHeatingDetail`. Defaults to 2
     (programmer + room thermostat) when the code is missing — the modal
     RdSAP case."""
@@ -389,7 +389,7 @@ def _control_type(main: Optional[MainHeatingDetail]) -> int:
 
 
 def _responsiveness(main: Optional[MainHeatingDetail]) -> float:
-    """SAP 10.3 Table 9b responsiveness R ∈ [0, 1]. Radiators ≈ 1.0;
+    """SAP 10.2 Table 9b responsiveness R ∈ [0, 1]. Radiators ≈ 1.0;
     underfloor ≈ 0.25. Defaults to radiators."""
     if main is None:
         return 1.0
@@ -656,7 +656,7 @@ def _water_efficiency_with_category_inherit(
 
 
 def _co2_factor_kg_per_kwh(main: Optional[MainHeatingDetail]) -> float:
-    """SAP 10.3 Table 12 CO2 emission factor by fuel code."""
+    """SAP 10.2 Table 12 CO2 emission factor by fuel code."""
     return co2_factor_kg_per_kwh(_main_fuel_code(main))
 
 

packages/domain/src/domain/sap/validation/parity_report.py

@@ -1,4 +1,4 @@
-"""Parity-validation report for the deterministic SAP 10.3 calculator.
+"""Parity-validation report for the deterministic SAP 10.2 calculator.
 
 ADR-0009 Session B compares `Sap10Calculator.calculate(epc).sap_score`
 to the cert's `energy_rating_current` across a 1000-cert stratified

packages/domain/src/domain/sap/worksheet/dimensions.py

@@ -1,4 +1,4 @@
-"""SAP 10.3 §1 — dwelling dimensions.
+"""SAP 10.2 §1 — dwelling dimensions.
 
 Builds the typed `Dimensions` aggregate that the rest of the worksheet
 reads: total floor area, volume, gross/party wall areas, ground and top
@@ -7,7 +7,7 @@ floor areas, perimeter. Geometry is summed across every entry in
 N parts produces totals over all N. Room-in-roof contributes one
 additional storey per part where present (RdSAP §1.8 + §3.9).
 
-Reference: SAP 10.3 specification (13-01-2026), §1 (pages 10-12); for
+Reference: SAP 10.2 specification (14-03-2025), §1 (pages 10-12); for
 existing dwellings see RdSAP 10 §3 (areas and dimensions).
 
 Edge cases explicitly out of scope for the first slice (see ADR-0009
@@ -34,7 +34,7 @@ _RR_SIMPLIFIED_STOREY_HEIGHT_M: Final[float] = 2.45
 
 @dataclass(frozen=True)
 class Dimensions:
-    """SAP 10.3 §1 geometric inputs to the monthly heat-balance loop."""
+    """SAP 10.2 §1 geometric inputs to the monthly heat-balance loop."""
 
     total_floor_area_m2: float
     volume_m3: float

packages/domain/src/domain/sap/worksheet/heat_transmission.py

@@ -98,7 +98,7 @@ class DwellingExposure:
     dwelling. Houses + bungalows expose both floor and roof; flats expose
     only the surfaces that aren't party with neighbouring dwellings.
 
-    SAP 10.3 §3 / RdSAP 10 §5: heat-transmission excludes party surfaces;
+    SAP 10.2 §3 / RdSAP 10 §5: heat-transmission excludes party surfaces;
     `party_walls_w_per_k` already captures the party-wall channel using
     its own U_party.
     """

packages/domain/src/domain/sap/worksheet/mean_internal_temperature.py

@@ -1,4 +1,4 @@
-"""SAP 10.3 mean internal temperature (Tables 9, 9b, 9c).
+"""SAP 10.2 mean internal temperature (Tables 9, 9b, 9c).
 
 The dwelling has two temperature zones during heating periods:
 
@@ -14,7 +14,7 @@ Standard SAP heating schedule:
 - 9 hours heating per day, two off-periods of 7 h and 8 h (control types 1, 2)
 - Control type 3 zones the heating: 9 h and 8 h off in 'elsewhere'
 
-Reference: SAP 10.3 specification (13-01-2026) Table 9 (page 183),
+Reference: SAP 10.2 specification (14-03-2025) Table 9 (page 183),
 Table 9b (page 184), Table 9c (page 185).
 """
 
@@ -63,7 +63,7 @@ def off_period_temperature_reduction_c(
     utilisation_factor: float,
     time_constant_h: float,
 ) -> float:
-    """SAP 10.3 Table 9b — temperature reduction `u` during a heating-off
+    """SAP 10.2 Table 9b — temperature reduction `u` during a heating-off
     period, in °C below the heating-period temperature.
 
         t_c   = 4 + 0.25 × τ

packages/domain/src/domain/sap/worksheet/rating.py

@@ -43,12 +43,12 @@ def energy_cost_factor(
     total_cost_gbp: float,
     total_floor_area_m2: float,
 ) -> float:
-    """SAP 10.3 §13 equation (7): ECF = 0.36 × cost / (TFA + 45)."""
+    """SAP 10.2 §13 equation (7): ECF = 0.36 × cost / (TFA + 45)."""
     return ENERGY_COST_DEFLATOR * total_cost_gbp / (total_floor_area_m2 + FLOOR_AREA_OFFSET_M2)
 
 
 def sap_rating(*, ecf: float) -> float:
-    """SAP 10.3 §13 equations (8)/(9). Un-rounded result so callers can
+    """SAP 10.2 §13 equations (8)/(9). Un-rounded result so callers can
     inspect the continuous value; `sap_rating_integer` rounds and clamps."""
     if ecf >= ECF_LOG_THRESHOLD:
         return _SAP_LOG_INTERCEPT - _SAP_LOG_SLOPE * log10(ecf)
@@ -56,7 +56,7 @@ def sap_rating(*, ecf: float) -> float:
 
 
 def sap_rating_integer(*, ecf: float) -> int:
-    """SAP 10.3 §13: round the continuous SAP rating to the nearest integer
+    """SAP 10.2 §13: round the continuous SAP rating to the nearest integer
     and clamp to a minimum of 1 ("if the result of the calculation is less
     than 1 the rating should be quoted as 1"). The integer value is the
     one published on the EPC."""
@@ -68,7 +68,7 @@ def environmental_impact_rating(
     co2_emissions_kg_per_yr: float,
     total_floor_area_m2: float,
 ) -> float:
-    """SAP 10.3 §14 equations (10)-(12). Un-rounded EI rating; mirrors the
+    """SAP 10.2 §14 equations (10)-(12). Un-rounded EI rating; mirrors the
     SAP rating curve but uses CO2 emissions per (TFA + 45) as the input."""
     cf = co2_emissions_kg_per_yr / (total_floor_area_m2 + FLOOR_AREA_OFFSET_M2)
     if cf >= _CF_LOG_THRESHOLD:

packages/domain/src/domain/sap/worksheet/solar_gains.py

@@ -1,4 +1,4 @@
-"""SAP 10.3 §6 + Appendix U §U3.2 — solar gains.
+"""SAP 10.2 §6 + Appendix U §U3.2 — solar gains.
 
 Two layers:
 
@@ -22,7 +22,7 @@ Defaults for g⊥ (Table 6b), FF (Table 6c), Z (Table 6d) are deferred to
 the cert→inputs mapper slice — this module takes them as caller inputs so
 its physics is independent of cert-shape assumptions.
 
-Reference: SAP 10.3 specification §6 + Appendix U §§U3.2-3.3 (pages
+Reference: SAP 10.2 specification §6 + Appendix U §§U3.2-3.3 (pages
 127-129); Table U5 columns map 8 cardinal cert orientations to 5
 coefficient sets (N, NE/NW, E/W, SE/SW, S).
 """
@@ -116,7 +116,7 @@ def surface_solar_flux_w_per_m2(
 ) -> float:
     """Per-orientation per-pitch monthly solar flux on a surface (W/m²).
 
-    SAP 10.3 Appendix U §U3.2 polynomial conversion from the horizontal
+    SAP 10.2 Appendix U §U3.2 polynomial conversion from the horizontal
     irradiance in Table U3 to any orientation/tilt combination.
     """
     s_h = horizontal_solar_irradiance_w_per_m2(region, month)
@@ -146,7 +146,7 @@ def window_solar_gain_w(
     frame_factor: float,
     overshading_factor: float,
 ) -> float:
-    """Solar gain through a window (W). SAP 10.3 §6.1 equation (5):
+    """Solar gain through a window (W). SAP 10.2 §6.1 equation (5):
 
         G_solar = 0.9 × A_w × S × g⊥ × FF × Z
 

packages/domain/src/domain/sap/worksheet/space_heating.py

@@ -1,4 +1,4 @@
-"""SAP 10.3 Table 9c step 10 — monthly space-heating requirement.
+"""SAP 10.2 Table 9c step 10 — monthly space-heating requirement.
 
 Final step of the heating worksheet: the heat the heating system has to
 deliver to maintain the mean internal temperature, given the loss rate to
@@ -10,7 +10,7 @@ the outside and the gains the dwelling has already accumulated.
 If Q_heat would be negative or below 1 kWh in any month, set it to 0 per
 the Table 9c clamp.
 
-Reference: SAP 10.3 specification (13-01-2026) Table 9c (page 185).
+Reference: SAP 10.2 specification (14-03-2025) Table 9c (page 185).
 """
 
 from __future__ import annotations
@@ -37,7 +37,7 @@ def monthly_heat_requirement_kwh(
     total_gains_w: float,
     days_in_month: int,
 ) -> float:
-    """SAP 10.3 Table 9c step 10. Returns delivered kWh required for the
+    """SAP 10.2 Table 9c step 10. Returns delivered kWh required for the
     month; clamps to 0 when below 1 kWh or negative."""
     loss_rate_w = heat_transfer_coefficient_w_per_k * (
         internal_temperature_c - external_temperature_c

packages/domain/src/domain/sap/worksheet/utilisation_factor.py

@@ -1,4 +1,4 @@
-"""SAP 10.3 Table 9a — heating utilisation factor η.
+"""SAP 10.2 Table 9a — heating utilisation factor η.
 
 η reduces the contribution of internal + solar gains when they outpace the
 dwelling's heat-loss rate. A well-insulated dwelling with large solar gains
@@ -16,7 +16,7 @@ The time constant τ = TMP / (3.6 × HLP) comes from the dwelling's thermal
 mass parameter and heat-loss parameter; computed by the orchestrator and
 passed in here.
 
-Reference: SAP 10.3 specification (13-01-2026) Table 9a (page 184).
+Reference: SAP 10.2 specification (14-03-2025) Table 9a (page 184).
 """
 
 from __future__ import annotations
@@ -28,7 +28,7 @@ def utilisation_factor(
     heat_loss_rate_w: float,
     time_constant_h: float,
 ) -> float:
-    """SAP 10.3 Table 9a heating utilisation factor η.
+    """SAP 10.2 Table 9a heating utilisation factor η.
 
     γ = total_gains_w / heat_loss_rate_w; η ∈ (0, 1]. When the heat-loss
     rate is non-positive (dwelling already balanced or gaining), η = 1