# Handover — post Slices S0380.164..169

Branch: `feature/per-cert-mapper-validation`. **HEAD `9ed003a5`**.
Predecessor: [`HANDOVER_POST_S0380_164.md`](HANDOVER_POST_S0380_164.md).

## TL;DR

Six slices landed in two phases:

**Phase 1 — cascade closure** (.164 + .165): closed the LAST two open
variants in the cascade-OK tier. `solid fuel 2` ΔCO2/ΔPE −93/-1027 →
±0.0000 (Elmhurst-mirror §12.4.4 summer-immersion double-count, new
§8.2 row). `pcdb 1` Δ−0.011 SAP → +0.0000 (§9.4.11 boiler-interlock
-5pp applied AFTER Eq D1 instead of before). The 41-variant heating-
systems corpus now has its 27-variant **cascade-OK tier fully EXACT**
on every metric (Σ|ΔSAP_c| ≈ 0.0001 ≈ floating-point noise).

**Phase 2 — mapper unblocks** (.166–.169): 11 of 16 blocked variants
unblocked via 4 mapper-extension slices. 7 EXACT on first try
(pcdb 3, electric 11/12/13/14, oil 2, oil 5); 4 land with cascade-side
residuals pinned as forcing functions (oil 3/4/6, no system).

| Slice | HEAD | Scope | Cascade-OK tier |
|---|---|---|---|
| S0380.164 | `302db131` | **§8.2 Elmhurst-mirror summer-immersion CO2/PE double-count.** §12.4.4 back-boiler HW blend adds `S_fuel × Table 12 annual electric` term on top of Table 12d/e monthly cascade for dual-rate tariffs. Closures: `solid fuel 2` ΔCO2/ΔPE → ±0.0000. Single-cert evidence flagged in new §8.2 row. | 25/25 EXACT |
| S0380.165 | `3de52bcb` | **§9.4.11 boiler-interlock -5pp applied AFTER Eq D1, not before.** Reciprocal Eq D1 weighting is non-linear in η; worksheet (217)m for pcdb 1 matches post-Eq-D1 form to 1e-4. New `interlock_penalty_pp` kwarg on `_apply_water_efficiency`. Closures: `pcdb 1` Δ−0.011 SAP / +£0.24 / +1.33 CO2 / +5.70 PE → ±0.0000. | 27/27 EXACT |
| S0380.166 | `589a8631` | **Bulk LPG mapper unblock.** `"Bulk LPG": 27` in `_ELMHURST_MAIN_FUEL_TO_SAP10`. Pcdb 3 EXACT first try. | 28/28 EXACT |
| S0380.167 | `7901dda4` | **Electric storage 11-14 unblock.** WEA / REA / OEA → 30. Electric 11/12/13/14 all EXACT first try. | 32/32 EXACT |
| S0380.168 | `58a95472` | **Bio-liquid oil 2-6 unblock + Table 32 FAME 5.44 → 7.64 (deferred .131 TODO).** BFD/BXE/BXF/BZC/B3C + 4 water labels. oil 2 (HVO) + oil 5 (Bioethanol) EXACT; oil 3/4 (FAME) closed 85 % of cost gap; oil 6 (B30K) carries cascade residual. | 34 EXACT + 3 pinned |
| S0380.169 | `9ed003a5` | **"No system" unblock per §A.2.2.** `"NON": 30`. Cascade lands with small residual pinned. | 34 EXACT + 4 pinned |

Extended handover suite at HEAD: **916 pass, 0 fail.** Pyright net-zero
(43 → 43).

## Current residual state at HEAD `9ed003a5`

### Cascade-OK tier (38 variants, up from 25)

**34 variants EXACT (|Δ| < 1e-3) on all 4 metrics.** 4 variants
carry pinned non-zero residuals (forcing functions):

| Variant | ΔSAP_c | Δcost | ΔCO2 | ΔPE | Notes |
|---|---:|---:|---:|---:|---|
| oil 3 | +2.59 | −£62 | −14.58 | −967 | FAME cascade HW kWh diff |
| oil 4 | +2.56 | −£57 | −13.35 | −885 | FAME cascade HW kWh diff |
| oil 6 | +3.05 | −£70 | −240.66 | −1113 | B30K SH/HW kWh gap |
| no system | +1.18 | −£27 | −49.83 | −562 | §A.2.2 portable-electric defaults |

All other 34 variants ±0.0000 on every metric.

### Blocked tier (5 variants — community heating)

Unchanged. `community heating 1/2/3/4/6`. **Deepest remaining tier:**
needs extractor field extraction + new community-fuel-type dispatch
in the mapper + cascade integration for heat-network paths (Table 12c
distribution loss, Table 12 heat-network codes 41/43/48/51/53/54).

## Open fronts ranked by leverage

### 1. **Community heating unblock — 5 variants** (next-session work)

The deepest remaining work. The Elmhurst Summary §14.1 lodges:

  Heating Type           Space and Water Heating
  Community Heat Source  Boilers / Combined Heat and Power / Heat pump
  Community Fuel Type    Mains Gas / Electricity / Mineral oil / Coal / ...

Variant breakdown:

  community heating 1 — COM + 301 + Boilers + Mains Gas    → code 51
  community heating 2 — COM + 302 + CHP + Mains Gas        → code 48
  community heating 3 — COM + 304 + Heat pump + Electricity → code 41
  community heating 4 — COM + 302 + CHP + Mineral oil      → code 48 (or 53 if not CHP)
  community heating 6 — COM + 302 + CHP + Coal             → code 48 (or 54 if not CHP)

The work spans three layers:

1. **Extractor**: extract Community Heat Source + Community Fuel Type
   strings into a new `CommunityHeating` dataclass on `ElmhurstSiteNotes`.
2. **Mapper**: `_resolve_community_heating_fuel_code(heat_source, fuel)`
   dispatch helper that maps the (heat_source, fuel) pair to the
   correct Table 12 heat-network code.
3. **Cascade**: ensure the heat-network path (Table 12c DLF age-band,
   PCDB Table 322 records if lodged, Table 12 note (k) DHW-only
   half-standing) handles all 5 sub-variants correctly.

Likely 2-3 slices total — start with the extractor + mapper, then
probe each variant's residual and close cascade gaps as they surface.

### 2. **oil 3 / oil 4 (FAME) cascade HW kWh gap**

Cascade HW kWh ~900 less than worksheet for oil 3/4 (FAME boilers).
Probably SAP 10.2 Table 4b code 128/129 has a non-standard summer
efficiency or Eq D1 path that the cascade isn't applying. Per-line
worksheet walk: cascade `_apply_water_efficiency` output vs (219)m
row.

### 3. **oil 6 (B30K) cascade SH + HW kWh gap**

Δcost −£70 on identical prices means kWh differs. Likely a different
Table 4b code-126 path. Closes ~£70 / 240 CO2 / 1113 PE.

### 4. **no system §A.2.2 cascade defaults**

ΔSAP +1.18 — cascade thinks dwelling is more efficient than worksheet.
Probable spec gap: §A.2.2 portable-electric defaults
(responsiveness / control-type / Table 11 secondary fraction). Per-
line walk on (210)m / (240) cost factor needed.

## Standard slice workflow (unchanged)

1. Read spec page + identify rule (or Elmhurst worksheet pattern)
2. Probe one 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. If mirroring Elmhurst against spec literal: add a row to
   `SAP_CALCULATOR.md §8 "Elmhurst-mirrored spec divergences"`. The
   ≥2-cert rule applies unless the new divergence shares its shape
   with an already-documented row (S0380.164 added §8.2 under this
   exception with a single-cert flag).
9. Commit with spec citation + `Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>`
10. Update `project-heating-systems-corpus` + `MEMORY.md` index

## Test baseline at HEAD `9ed003a5`

```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: **916 pass, 0 fail.**

## Memories to load (in order)

```
project-heating-systems-corpus            # HEAD 9ed003a5
feedback-sap-10-2-only-never-10-3
feedback-software-no-special-handling
feedback-spec-floor-skepticism
feedback-worksheet-not-api-reference
feedback-spec-citation-in-commits
feedback-verify-handover-claims
feedback-zero-error-strict
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
feedback-bigger-slices-for-uniform-work
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.
- **Don't re-investigate Slices .91..169** — all settled.
- **Don't add new helpers to `domain/sap10_ml/`** — on deprecation path.
- **Don't treat ΔSAP=0.07 as "closed"** — target is <1e-4 vs worksheet.

## Master doc

The canonical architecture + API + validation doc lives at
[`domain/sap10_calculator/docs/SAP_CALCULATOR.md`](SAP_CALCULATOR.md)
(7 sections + §8 with .1 and .2 entries). S0380.164 added §8.2 for
the §12.4.4 summer-immersion double-count.

## Good luck.