docs: handover post S0380.156..159

Captures the per-line walk discipline used to close electric 2 + 5
across four slices (.156 Table 3 WHC=903 primary-loss, .157 Table 2b
note b) WHC=903 ×0.9, .158 Table 4f warm-air heating fans, .159
Table 4a Cat 7 R tariff-aware dispatch). Σ |ΔSAP_c| across the
25-variant heating-systems corpus dropped from 2.87 → 1.21 (58%
reduction). All variants now sit under 0.3 SAP.

Next-slice candidate: the 9-variant cluster at ±0.09..0.12 SAP
(electric 3/5/6/7/8/9 + sf 4/9/10/11) — uniform pattern suggesting
a shared shave-the-residual fix. Worth a per-line walk on one
cluster variant before accepting the prior "Elmhurst-vs-spec quirk"
framing.

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

domain/sap10_calculator/docs/HANDOVER_POST_S0380_159.md

@@ -0,0 +1,303 @@
+# Handover — post Slices S0380.156..159
+
+Branch: `feature/per-cert-mapper-validation`. **HEAD `fba45d11`**.
+Predecessor: [`HANDOVER_POST_S0380_155.md`](HANDOVER_POST_S0380_155.md).
+
+## TL;DR
+
+Four slices landed — three closed the electric 2 (Cat 5 warm-air ASHP
+code 524) cohort entry point, one closed the electric 5 (Cat 7
+slimline storage code 402 + 18-hour tariff) entry point. All four
+came from the same per-line walk discipline: dump the worksheet
+section the residual landed in, identify the diverging line ref,
+look up the spec rule.
+
+| Slice | Commit | Spec rule closed |
+|---|---|---|
+| S0380.156 | `02092c80` | SAP 10.2 Table 3 (p.160) zero-loss list — universal WHC=903 guard at top of `_primary_loss_applies`. Cat-4 HP branch was falsely returning True when WHC=903 means electric immersion (no primary circuit). |
+| S0380.157 | `a2a4b682` | SAP 10.2 Table 2b note b) (p.159) "×0.9 if separate DHW timing (boiler / warm-air / HP)". Companion WHC=903 guard at top of `_separately_timed_dhw`. Electric immersion is not in the verbatim system-type list. |
+| S0380.158 | `8843df1b` | SAP 10.2 Table 4f (p.174) row "Warm air heating system fans" = SFP × 0.4 × V per footnote e default SFP = 1.5 W/(l/s). New `_TABLE_4A_WARM_AIR_SAP_CODES` frozenset (22 codes) + leaf helper. |
+| S0380.159 | `fba45d11` | SAP 10.2 Table 4a (p.166) Cat 7 R splits between Off-peak (codes 402/403 R=0.2) and 24-hour heating tariff (R=0.4). Per §12.4.3 the 18-hour tariff has 18h low-rate availability ≈ continuous charging → routes to the 24-hour Table 4a R sub-row for codes 402/403/405/406. |
+
+Extended handover suite at HEAD: **903 pass, 0 fail.** Pyright net-zero
+(43 → 43). Σ |ΔSAP_c| across the 25-variant cohort: **2.87 → 1.21**
+(58% reduction across 4 slices over one session).
+
+## Disciplines reinforced this session
+
+1. **Per-line walk → spec → fix.** Every closure came from dumping the
+   failing variant's worksheet line-by-line:
+   - .156: cascade `primary_loss_monthly_kwh_annual = 509.98` vs
+     worksheet (59)m = 0 every month → Table 3 zero-loss line.
+   - .157: cascade `solar_storage_monthly_kwh_annual = 403.87` vs
+     worksheet (56) = 448.73 → ratio = 0.9 exactly → Table 2b note b.
+   - .158: cascade `pumps_fans_kwh_per_yr = 0` vs worksheet (249) =
+     136.35 → Table 4f warm-air fans = 1.5 × 0.4 × 227.25.
+   - .159: cascade T_living = 20.12 vs worksheet 19.6519 → all MIT
+     inputs match → back-solve from Tsc formula isolates R as the
+     only divergence → Table 4a Cat 7 24-hour sub-row.
+
+2. **Companion WHC=903 fixes.** S0380.156 and .157 both added a guard
+   at the **top** of a predicate that already had logic for the same
+   case lower down. The Cat-4 HP early-return was masking the
+   downstream electric-immersion / electric-water checks. Pattern:
+   when a predicate has a per-system-category early-return, the
+   data-shape gate (here WHC=903) needs to come **first**.
+
+3. **Spec docstring flagged the gap before it surfaced.** S0380.159
+   closed a TODO already noted in the source — the existing
+   `_RESPONSIVENESS_BY_SAP_CODE` dict comment said "promote to
+   (sap_code, tariff) lookup when 24-hour fixture surfaces; until
+   then the off-peak default applies (under-shoots R for the
+   24-hour case)." The 18-hour fixture surfaces in this corpus.
+
+## Current residual state at HEAD `fba45d11`
+
+### Cascade-OK tier (25 variants on pin grid)
+
+Sorted by |ΔSAP_c|:
+
+| Variant | ΔSAP_c | Δcost | ΔCO2 | ΔPE | Notes |
+|---|---:|---:|---:|---:|---|
+| oil 1 | **-0.0000** | **-0.00** | **+0.00** | **+0.00** | EXACT |
+| oil pcdb 1 | **+0.0000** | **+0.00** | **-0.00** | **+0.00** | EXACT |
+| oil pcdb 2 | **+0.0000** | **+0.00** | **-0.00** | **+0.00** | EXACT |
+| oil pcdb 3 | **+0.0000** | **+0.00** | **+0.00** | **-0.00** | EXACT |
+| electric 1 | **-0.0000** | **-0.00** | +11.95 | +48.66 | SAP/cost exact, lighting-PE quirk |
+| solid fuel 5 | **+0.0000** | **+0.00** | +11.95 | +48.66 | same lighting-PE quirk |
+| solid fuel 6 | **+0.0000** | **+0.00** | +11.95 | +48.66 | same |
+| solid fuel 7 | **-0.0000** | **+0.00** | +11.95 | +48.66 | same |
+| solid fuel 8 | **-0.0000** | **+0.00** | +11.95 | +48.66 | same |
+| solid fuel 2 | **-0.0000** | **-0.00** | -93.10 | -1027.51 | SAP/cost exact, §12.4.4 blend artifact |
+| solid fuel 3 | **-0.0000** | **-0.00** | +0.00 | -0.00 | EXACT |
+| pcdb 1 | -0.0108 | +£0.24 | +1.33 | +5.70 | basically exact |
+| gshp | -0.0178 | +£0.41 | +7.06 | +33.52 | basically exact |
+| ashp | -0.0240 | +£0.55 | +7.33 | +36.34 | basically exact |
+| solid fuel 4 | +0.0850 | -£1.96 | -9.31 | -5.78 | cluster |
+| solid fuel 11 | +0.0912 | -£2.10 | +10.55 | -0.74 | cluster |
+| electric 8 | +0.0941 | -£2.17 | +7.92 | +6.58 | cluster |
+| electric 7 | +0.1017 | -£2.34 | +7.64 | +3.10 | cluster |
+| **electric 5** | **+0.1081** | **-£2.49** | **+7.30** | **+0.07** | **CLOSED in .159 — was -1.18** |
+| electric 6 | +0.1081 | -£2.49 | +7.32 | +0.16 | cluster |
+| solid fuel 9 | +0.1072 | -£2.47 | +9.69 | -5.07 | cluster |
+| **electric 2** | **-0.1087** | **+£2.50** | **+16.54** | **+97.69** | **CLOSED in .156-.158 — was -0.46** |
+| solid fuel 10 | +0.1134 | -£2.61 | +9.31 | -13.91 | cluster |
+| electric 9 | +0.1199 | -£2.76 | +6.82 | -4.51 | cluster |
+| electric 3 | +0.1215 | -£2.80 | +6.72 | -5.99 | cluster |
+
+**Σ |ΔSAP_c| = 1.21** (was 2.87 at start of S0380.156).
+**Σ |ΔCO2| = 267.67 kg** (was ~310).
+**Σ |ΔPE| = 1489.96 kWh** (was ~2400 — driven by 5-variant lighting cluster + sf2).
+
+Buckets:
+- **EXACT** (|Δ|<1e-4): **11/25** (44%)
+- **basically exact** (|Δ|<0.05): 3/25 (ashp/gshp/pcdb1)
+- **mid** (0.05..0.3): 11/25 — the 9-variant cluster (electric 3/5/6/7/8/9 + sf 4/9/10/11) + electric 2
+- **big** (>=0.3): **0/25** — all variants now under 0.3 SAP
+
+### Blocked tier (16 variants — `MissingMainFuelType`)
+
+Unchanged. Community heating × 5, electric storage 11-14, no system,
+oil 2-6, pcdb 3.
+
+## Open fronts ranked by leverage
+
+### 1. The 9-variant cluster — ±0.09..0.13 SAP / −£2..−£3 / +£7 CO2 / small PE
+
+electric 3, electric 5, electric 6, electric 7, electric 8, electric 9,
+solid fuel 4, solid fuel 9, solid fuel 10, solid fuel 11 — plus
+similar magnitudes on electric 5 post-.159.
+
+The pattern is uniform:
+- ΔSAP +0.085 .. +0.121 (always positive — cascade SAP higher than worksheet)
+- Δcost −£1.96 .. −£2.80 (cascade cost lower — under-charging by ~38 kWh × 7.41 p/kWh)
+- ΔCO2 +6.72 .. +10.55 kg (cascade over-emitting)
+- ΔPE −13.91 .. +6.58 kWh (small, both signs)
+
+The cost gap is consistent with cascade SH demand being **~38 kWh
+lower** than worksheet. Diagnostic from earlier probing on electric
+3 / 6: cascade SH_demand ≈ 11050 vs worksheet (98c) ≈ 11088 (diff
+−38 kWh per variant).
+
+**Hypothesis (per [[feedback-spec-floor-skepticism]] — verify before
+accepting)**: prior handover ranked this cluster as "lowest leverage —
+probably Elmhurst-vs-spec PE/CO2 monthly factor pattern". After .159
+closed electric 5 from ALSO being in this pattern, that hypothesis
+looks weaker — the same cluster shape may have a clean spec citation.
+Suggested probe:
+- Pick one cluster variant (electric 3 or solid fuel 4) and run a
+  per-line walk against the worksheet (98c)/(211)/(255).
+- The −£2.50 cost suggests **38 kWh SH demand difference**. Where?
+- Check §8 step 10 `Qheat = 0.024 × (Lm − η·Gm) × nm` line refs vs
+  worksheet (98a). If cascade Qheat is off, look upstream at (97).
+- Closing this cluster would shave **Σ|ΔSAP| from 1.21 → ~0.10** in
+  one slice. **Highest leverage today.**
+
+### 2. Electric 2 follow-up — −0.11 SAP / +£2.50 cost / +£16 CO2 / +£98 PE
+
+Cascade now overshoots after .156-.158 wired the missing
+primary-loss / storage-loss / warm-air-fan components correctly.
+Likely a small upstream SH cascade gap (cascade SH demand +57 kWh
+over worksheet — Cat 5 warm-air HP specific). The +136 kWh warm-air
+fan electricity bills at 18-hour high rate → adds £18.64 + 18.54 kg
+CO2 + 204 kWh PE. The over-shoot of +£2.50 / +£16 CO2 / +£98 PE
+roughly matches the magnitude → suggests one of:
+- The warm-air fan should bill at a different rate (Table 12a
+  fraction for ALL_OTHER_USES on 18-hour vs the Appendix F2 rate).
+- The fan power should be lower for Cat 5 HPs (different SFP than
+  the default 1.5 W/(l/s)).
+- Some other small Cat 5 / warm-air HP specific rule.
+
+**Suggested probe**: dump the worksheet (249) cost line carefully —
+worksheet shows 136.35 × 13.67 = £18.64. Cascade should compute the
+same. If Δcost ≠ +£18.64, then the fan kWh is right but the rate is
+not. If Δcost = +£18.64, the fan kWh shouldn't be there at all on
+this row (maybe it goes to a different (249)b line).
+
+### 3. Lighting-only PE +48.66 cohort — 5 variants — **DEFERRED**
+
+electric 1, solid fuel 5/6/7/8. SAP/cost EXACT; PE +48.66 / CO2
++11.95 from Elmhurst using Table 12 ANNUAL factor for off-peak HW
+immersion split. Spec Table 12d/12e header mandates MONTHLY factors.
+Closing it violates spec.
+
+### 4. Mapper-extension unblocking (16 blocked variants)
+
+- Community heating × 5 — extend extractor for §14.1 block.
+- Electric storage 11-14 — extend `_ELMHURST_MAIN_HEATING_EES_TO_FUEL_CODE`
+  for EES codes WEA, REA, OEA.
+- "No system" — spec-assumed direct electric.
+- Oil 2-6 — Table 4b non-oil liquid fuels (HVO/FAME/B30K/bioethanol).
+- pcdb 3 — `"Bulk LPG"` mapper dict gap.
+
+Separate from cascade closure work. Each unblock = one mapper slice.
+
+## Slice history (this session)
+
+| Slice | HEAD | Scope |
+|---|---|---|
+| S0380.156 | `02092c80` | SAP 10.2 Table 3 (PDF p.160) zero-loss list — universal WHC=903 guard at the top of `_primary_loss_applies`. New `_WHC_ELECTRIC_IMMERSION: Final[int] = 903` constant. Pre-slice the Cat 4 HP branch returned True unconditionally when no PCDB record was lodged → electric 2 cascade falsely added ~510 kWh/yr primary loss. Closures electric 2: HW kWh 2849 → 2339, ΔSAP −0.46 → +0.81 (residual swung past — exposed offsetting bugs). Δcost +£10.56 → −£18.71, ΔPE +443 → −162. |
+| S0380.157 | `a2a4b682` | SAP 10.2 Table 2b note b) (PDF p.159) — companion WHC=903 guard at top of `_separately_timed_dhw`. Pre-slice the Cat 4 HP branch fired before the existing `_is_electric_water` check could route to False; cascade applied ×0.9 to (53) Temperature Factor on an immersion-fed cylinder. Reuses `_WHC_ELECTRIC_IMMERSION`. Closures electric 2: storage loss 403.87 → 448.73 EXACT, HW kWh 2339 → 2384.12 EXACT match worksheet, ΔSAP +0.81 → +0.70. |
+| S0380.158 | `8843df1b` | SAP 10.2 Table 4f (PDF p.174) row "Warm air heating system fans" = SFP × 0.4 × V per footnote e default SFP = 1.5 W/(l/s). New `_TABLE_4A_WARM_AIR_SAP_CODES` frozenset (22 codes: Cat 5 HPs 521/523-527 + Cat 9 warm-air 501-515/520) + leaf helper `_table_4f_warm_air_heating_fans_kwh(main, dwelling_volume_m3, has_balanced_mv)`. Footnote-e balanced-MV omission via `_has_balanced_mechanical_ventilation` predicate. Closures electric 2: pumps_fans 0 → 136.35 EXACT, ΔSAP +0.70 → −0.11, Δcost −£16.14 → +£2.50. |
+| S0380.159 | `fba45d11` | SAP 10.2 Table 4a (PDF p.166) Cat 7 R splits Off-peak vs 24-hour heating tariff sub-rows. Per §12.4.3 the 18-hour tariff has 18h low-rate availability ≈ continuous charging. New `_CONTINUOUS_CHARGING_TARIFFS = {EIGHTEEN_HOUR, TWENTY_FOUR_HOUR}` + `_RESPONSIVENESS_24_HOUR_OVERRIDE_BY_SAP_CODE` (codes 402/403/405/406). `tariff: Optional[Tariff]` parameter added to `_responsiveness`; threaded through both MIT cascade call sites. Closures electric 5: ΔSAP −1.18 → +0.11 (91% reduction), Δcost +£27.09 → −£2.49, ΔPE +438 → +0.07 EXACT. Electric 5 now joins the 9-variant cluster pattern. |
+
+## Standard slice workflow (unchanged)
+
+1. Read spec page + identify rule
+2. Probe one cluster variant; verify diagnosis via monkey-patch / direct walk
+3. Write failing AAA test (literal `# Arrange / # Act / # Assert`)
+4. Implement helper / dispatch entry / mapper extension
+5. Re-pin affected variants (DO NOT widen tolerance)
+6. Run extended handover suite (command below)
+7. Pyright net-zero check (`git stash` → pyright → `git stash pop` → pyright)
+8. Commit with spec citation + `Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>`
+9. Update `project-heating-systems-corpus` + `MEMORY.md` index
+
+## Test baseline at HEAD `fba45d11`
+
+```bash
+PYTHONPATH=/workspaces/model python -m pytest \
+    backend/documents_parser/tests/test_summary_pdf_mapper_chain.py \
+    backend/documents_parser/tests/test_heating_systems_corpus.py \
+    backend/documents_parser/tests/test_elmhurst_extractor.py \
+    backend/documents_parser/tests/test_elmhurst_end_to_end.py \
+    domain/sap10_calculator/worksheet/tests/test_e2e_elmhurst_sap_score.py \
+    domain/sap10_calculator/worksheet/tests/test_heat_transmission.py \
+    domain/sap10_calculator/worksheet/tests/test_internal_gains.py \
+    domain/sap10_calculator/worksheet/tests/test_solar_gains.py \
+    domain/sap10_calculator/worksheet/tests/test_dimensions.py \
+    domain/sap10_calculator/worksheet/tests/test_rating.py \
+    domain/sap10_calculator/worksheet/tests/test_ventilation.py \
+    domain/sap10_calculator/worksheet/tests/test_appendix_h_solar.py \
+    domain/sap10_calculator/worksheet/tests/test_mev.py \
+    domain/sap10_calculator/rdsap/tests/test_cert_to_inputs.py \
+    domain/sap10_calculator/rdsap/tests/test_golden_fixtures.py \
+    domain/sap10_calculator/tests/test_pcdb_table_322_lookup.py \
+    domain/sap10_calculator/tests/test_pcdb_table_329_lookup.py \
+    domain/sap10_calculator/tests/test_table_12a.py \
+    --no-cov -q
+```
+
+Expected: **903 pass, 0 fail.**
+
+## Memories to load (in order)
+
+```
+project-heating-systems-corpus            # HEAD fba45d11
+feedback-sap-10-2-only-never-10-3         # CRITICAL — never reference SAP 10.3
+feedback-software-no-special-handling     # CRITICAL — apply spec uniformly
+feedback-spec-floor-skepticism            # CUTS BOTH WAYS — skeptical of your OWN audit narrative
+feedback-worksheet-not-api-reference
+feedback-spec-citation-in-commits
+feedback-verify-handover-claims
+feedback-zero-error-strict                # TARGET: ΔSAP_c < 1e-4 vs worksheet
+feedback-commit-per-slice
+feedback-aaa-test-convention
+feedback-e2e-validation-philosophy
+feedback-abs-diff-over-pytest-approx
+feedback-golden-residuals-near-zero
+feedback-one-e-minus-4-across-the-board
+reference-unmapped-sap-code
+reference-unmapped-api-code
+project-oil-price-spec-divergence
+```
+
+## What NOT to do
+
+- **Don't reference SAP 10.3** — track 10.2 deliberately.
+- **Don't widen pin tolerances** — re-pin smaller or find the spec gap.
+- **Don't add empirical gates** to keep cohort pins stable when a
+  spec rule clearly applies.
+- **Don't re-investigate Slices .91..159** — all settled.
+- **Don't add new helpers to `domain/sap10_ml/`** — on deprecation
+  path; `domain/sap10_calculator/tables/` is the canonical home.
+- **Don't treat ΔSAP=0.07 as "closed"** — target is <1e-4 vs worksheet.
+- **Don't try to close the lighting-PE +48.66 cluster** — it's an
+  Elmhurst-vs-spec quirk that closing would violate spec.
+- **Don't form a spec hypothesis without per-line data** — walk the
+  worksheet line-by-line for the failing variant first.
+
+## Spec source quick-reference
+
+All under `domain/sap10_calculator/docs/specs/`:
+
+- **SAP 10.2 full spec**: `sap-10-2-full-specification-2025-03-14.pdf`
+  - **§4** (p.135-137) — water heating worksheet (45..65)
+  - **§7** (p.26) — Mean internal temperature
+  - **§9.2.4** (p.27) — Solid fuel boiler systems
+  - **§9.4.11** (p.30) — Boiler interlock: -5pp to BOTH SH and DHW
+  - **§9.4.19** (p.34-35) — Storage heater controls
+  - **§12.4.3** (p.36) — Electric tariff types (7-hour / 10-hour /
+    18-hour / 24-hour heating). **Slice .159.**
+  - **§12.4.4** (p.36-37) — Solid fuel back-boiler summer immersion.
+    **Slice .154.**
+  - **§A.2.2** (~p.189) — Forced-secondary set
+  - **Appendix D §D2.1 (2)** (p.57) — Eq D1 monthly water eff cascade
+  - **Appendix F2** (p.63) — 18-hour CPSU
+  - **Appendix N3** (p.107-109) — Heat pump DHW efficiency cascade
+  - **Table 2b** (p.159) — Cylinder temperature factor + note b ×0.9
+    rule for boiler/warm-air/HP. **Slice .157.**
+  - **Table 3** (p.160) — Primary circuit loss; zero-loss list incl.
+    electric immersion. **Slices .152 / .153 / .156.**
+  - **Table 4a** (p.163-170) — heating systems + R splits between
+    Off-peak and 24-hour heating tariff for Cat 7 electric storage.
+    **Slices .155 / .159.**
+  - **Table 4b** (p.168) — gas/liquid boilers seasonal efficiency
+  - **Table 4e** (p.171-173) — heating system controls + temperature
+    adjustment column. Group 4 storage controls 2401/2402/2403.
+  - **Table 4f** (p.174) — pumps + fans (incl. warm-air row).
+    **Slice .158.**
+  - **Tables 9 / 9a / 9b / 9c** (p.182-184) — heating periods, MIT
+    cascade, T_sc formula. Used in .159 back-solve.
+  - **Table 11** (p.188) — secondary heating fraction
+  - **Table 12** (p.191) — SAP rating fuel prices + standing charges
+  - **Table 12a** (p.191) — high/low-rate fraction by system × tariff
+  - **Table 12d/12e** (p.195-196) — monthly variation in CO2/PE factors
+  - **Table 13** (p.197) — high-rate fraction for electric DHW
+- **RdSAP 10 spec**: `RdSAP 10 Specification 10-06-2025.pdf`
+  - **§4.1 Table 5** (p.28) — Ventilation parameters
+  - **§5** (p.29) — Floor infiltration spec rule
+  - **§10.11 Table 29** (p.56) — Heating/HW parameters
+  - **§19 Table 32** (p.95) — RdSAP10 fuel prices / CO2 / PE
+
+## Good luck.