# Handover — post Slices S0380.131..137

Branch: `feature/per-cert-mapper-validation`. **HEAD `3542186f`**.
Predecessor: [`HANDOVER_POST_S0380_130.md`](HANDOVER_POST_S0380_130.md).

## TL;DR

Seven slices landed on top of `c8486077`. The work spanned a fuel-price
correction, a strict-raise on missing fuel that surfaced 26 corpus
variants relying on a silent mains-gas default, a measurement-bug fix
in the corpus's PE pin, and three slices closing per-cluster cascade
gaps via SAP 10.2 Table 4a R-dispatch + a canonical electric-fuel
classifier.

| Slice | Commit | Scope |
|---|---|---|
| **S0380.131** | `14eee259` | Heating-oil price 7.64 → 5.44 (empirical, Elmhurst worksheet + cert 0240 back-solve) |
| **S0380.132** | `0aa40b63` | `MissingMainFuelType` strict-raise on empty `main_fuel_type` (26 corpus variants moved to `_BLOCKED_BY_MISSING_MAIN_FUEL_TYPE`) |
| **S0380.133** | `0d2d41ab` | Elmhurst §14.0 EES Code → Table 32 fuel code (BAF/BAI/RAM=anthracite, BCC=coal, BDI=dual, BKI=smokeless, BQI=wood chips, RPS=pellets bags, RUN=bulk, RWN=wood logs) — 10 solid-fuel variants unblocked |
| **S0380.134** | `7530ed3f` | Corpus PE pin compared against `cert_to_demand_inputs` (EPC block) instead of rating mode (rating block has no Total PE row) |
| **S0380.135** | `829a3318` | Table 4a R-dispatch in `_responsiveness` keyed on `sap_main_heating_code` (solid-fuel codes 151-161, 631-636) |
| **S0380.136** | `4d004790` | `_is_electric_main` / `_is_electric_water` route via canonical T32-first normaliser (`table_32.is_electric_fuel_code`) — closes solid fuel 6 dual-fuel SAP −11.37 → +1.95 |
| **S0380.137** | `3542186f` | Table 4a R-dispatch extended to electric storage / UFH / Electricaire / direct-acting / ceiling (codes 401-409, 421-425, 515, 691, 694, 701) |

Extended handover suite at HEAD: **880 pass, 0 fail**.

## What changed

### Spec compliance (Table 4a + Table 32 + spec line 15271)

S0380.135 + S0380.137 implement SAP 10.2 spec line 15271:

> "R = responsiveness of main heating system (Table 4a or Table 4d)"

Pre-slices the cascade only consulted Table 4d (emitter-based) — Table
4a's per-heating-system R (typically lower than 1.0 for non-modulating
systems) was silently ignored. The new
`_RESPONSIVENESS_BY_SAP_CODE` dispatch in
[`cert_to_inputs.py`](../rdsap/cert_to_inputs.py) overrides the
Table 4d fallback when the SAP code is in the dict (31 entries
covering all solid-fuel + electric storage / UFH / direct-acting /
ceiling codes from Table 4a p.169-170).

S0380.131 corrected `tables/table_32.py` heating oil 7.64 → 5.44
(empirical, no spec citation possible — RdSAP 10 spec PDF p.95 is
outlier vs Elmhurst worksheet + gov.uk register back-solve).

### Strict-raise + canonical normalisation pattern

S0380.132 added `MissingMainFuelType(ValueError)` in
[`exceptions.py`](../exceptions.py). `_main_fuel_code` raises when
the mapper leaves `main_fuel_type` empty / non-int. This surfaced 26
of 41 corpus variants relying on the silent mains-gas default.

S0380.136 promoted `table_32._is_electric_code` to public
`is_electric_fuel_code` and routed `_is_electric_main` /
`_is_electric_water` through it. Closed an API/Table-32 code-10
collision (API 10 = electricity, T32 10 = dual fuel) that re-routed
solid fuel 6's cost through off-peak electric tariff.

### Mapper extraction extensions

S0380.133 added `main_heating_ees: str` field to
[`elmhurst_site_notes.py:MainHeating`](../../../datatypes/epc/surveys/elmhurst_site_notes.py)
and extraction in
[`elmhurst_extractor.py`](../../../backend/documents_parser/elmhurst_extractor.py),
plus `_ELMHURST_MAIN_HEATING_EES_TO_FUEL_CODE` dict in
[`mapper.py`](../../../datatypes/epc/domain/mapper.py) (10 entries
keyed on 3-letter EES code).

### Corpus test structure

[`test_heating_systems_corpus.py`](../../../backend/documents_parser/tests/test_heating_systems_corpus.py)
now has three tiers:

1. `_EXPECTATIONS` (25 variants) — full residual-pin grid:
   SAP / cost / CO2 from `cert_to_inputs` (rating block), PE from
   `cert_to_demand_inputs` (EPC block).
2. `_BLOCKED_BY_MISSING_MAIN_FUEL_TYPE` (16 variants) — assert-on-raise
   tier driving
   `test_heating_systems_corpus_blocked_variant_raises_missing_main_fuel_type`.
3. Each variant covered exactly once across the two tiers (41 total).

## Current residual cluster at HEAD `3542186f`

### Solid fuel — 10/10 unblocked, tight cluster

| variant | SAP code | R | ΔSAP | ΔPE |
|---|---:|---:|---:|---:|
| solid fuel 2 | 158 | 0.50 | +2.64 | -1211 |
| solid fuel 3 | 160 | 0.50 | +1.32 | -935 |
| solid fuel 4 | 633 | 0.50 | +1.59 | +151 |
| solid fuel 5 | 153 | 0.75 | +1.70 | +160 |
| solid fuel 6 | 160 | 0.50 | +1.95 | +87 |
| solid fuel 7 | 160 | 0.50 | +2.04 | +44 |
| solid fuel 8 | 160 | 0.50 | +1.81 | +88 |
| solid fuel 9 | 636 | 0.75 | +1.71 | +155 |
| solid fuel 10 | 634 | 0.50 | +1.75 | +120 |
| solid fuel 11 | 634 | 0.50 | +1.62 | +171 |

7/10 PE residuals within ±220 kWh. SAP cluster all +1.32 to +2.64.
solid fuel 2 (-1211 PE) + solid fuel 3 (-935 PE) are the remaining
outliers — likely Table 4a efficiency variant or kWh-totals issue.

### Electric direct-acting — 6/7 unblocked, +5..+9 SAP cluster open

| variant | SAP code | R | ΔSAP | Δcost | ΔPE |
|---|---:|---:|---:|---:|---:|
| electric 1 | 191 | 1.00 | +9.64 | −£222 | +165 |
| electric 2 | 524 | 1.00 | +5.85 | −£135 | +971 |
| electric 3 | 401 | 0.00 | +9.43 | −£217 | -1059 |
| electric 5 | 402 | 0.20 | +6.76 | −£156 | -96 |
| electric 6 | 404 | 0.40 | +7.82 | −£180 | -494 |
| electric 7 | 408 | 0.60 | +7.58 | −£175 | -428 |
| electric 8 | 409 | 0.80 | +5.84 | −£135 | +200 |
| electric 9 | 421 | 0.00 | +6.77 | −£156 | +154 |

**Shared pattern across all 7:** SAP +5.8..+9.6 with cost −£135..−£222.
Consistent cost under-count strongly suggests a single Table 12a
high/low-rate fraction handling bug OR a pumps/fans electric cascade
gap. Same "one fix many variants" leverage pattern as previous slices.

### Other cascade-OK variants

| variant | ΔSAP | ΔPE | notes |
|---|---:|---:|---|
| ashp | +5.67 | -12 | ✓ PE closed |
| gshp | +5.16 | -455 | |
| oil 1 | +2.66 | -1050 | |
| oil pcdb 1/2 | +0.42 | -84 | ✓ basically closed |
| oil pcdb 3 | +1.16 | -271 | |
| pcdb 1 | +6.95 | -3135 | largest open PE |

### Blocked tier (16 variants in `_BLOCKED_BY_MISSING_MAIN_FUEL_TYPE`)

| Category | Variants | SAP code(s) | EES code(s) | Likely fix |
|---|---|---|---|---|
| Community heating | 1, 2, 3, 4, 6 | 301-304 | COM (all share) | Derive fuel from §14.1 Community Heating block |
| Electric storage | 11, 12, 13, 14 | 515, 691, 701 | WEA, REA, OEA | Extend `_ELMHURST_MAIN_HEATING_EES_TO_FUEL_CODE` to electric EES codes |
| No system | (1) | 699 | NON | Spec assumed electric heaters |
| Liquid-fuel non-oil | oil 2-6 | Table 4b 126-141 | BFD, BXE, BXF, BZC, B3C | Extend §15.0 fallback / mapper dict for HVO / FAME / B30K / bioethanol |
| PCDB Bulk LPG | pcdb 3 | (PCDB) | (absent) | Add `"Bulk LPG"` → 2 to `_ELMHURST_MAIN_FUEL_TO_SAP10` |

## Test baseline at HEAD `3542186f`

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

## Memories to load (in order)

```
project-heating-systems-corpus    # full state at HEAD 3542186f
feedback-sap-10-2-only-never-10-3 # CRITICAL — never reference SAP 10.3
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-spec-floor-skepticism
feedback-golden-residuals-near-zero
feedback-one-e-minus-4-across-the-board
reference-unmapped-sap-code       # updated S0380.135 + S0380.137
reference-unmapped-api-code
project-oil-price-spec-divergence # S0380.131 detail
```

## Next-slice candidates (in priority order)

### 1. Electric +5..+9 SAP cluster — highest leverage

7 electric corpus variants share +5.8..+9.6 SAP and −£135..−£222 cost
under-count. Pattern strongly suggests one shared cascade gap. Likely
candidates:

- **Table 12a high/low-rate fraction** for electric main heating —
  the cascade applies tariff splits per `space_heating_high_rate_fraction`,
  but the worksheet may use a different fraction or skip the split.
- **Pumps/fans kWh / cost** — cascade reports 130 kWh/yr; worksheet
  reports 41 kWh/yr. Cascade over-counts by 89 kWh × electric ~13 p/kWh
  = ~£12 — small, not the dominant cost gap.
- **Cost factor cascading** — for electric main on 18-hour tariff, the
  cascade uses 5.50 p/kWh (off-peak low rate). The worksheet uses... need
  to probe.

Probing one variant (electric 3, the worst at +9.43 SAP / -£217 cost)
would identify the shared cause. If a single Table 12a / tariff fix
closes most of the 7, that's a high-value slice.

### 2. Unblock community heating cluster

5 community heating variants all share `EES Code: COM` (no fuel info in
the EES code). The fuel must be derived from the §14.1 Community
Heating/Heat Network block which lodges the heat source type (gas
boiler / CHP / heat pump / etc.). Each maps to a Table 32 heat-network
code (51-58, 41-49).

Implementation pattern: extend the extractor to capture §14.1 community
heat source, add a SAP-code-301-304 → community-heating-fuel dispatch
in the mapper.

### 3. Unblock electric storage variants (11, 12, 13, 14)

4 electric corpus variants blocked because mapper has no fuel. SAP
codes 515 (Electricaire), 691 (Panel heaters), 701 (Electric ceiling)
imply electric. Extend `_ELMHURST_MAIN_HEATING_EES_TO_FUEL_CODE`:

| EES | Variant | Fuel |
|---|---|---|
| WEA | electric 11 (SAP 515) | 30 (standard electric) |
| REA | electric 12 (SAP 691) | 30 |
| OEA | electric 13/14 (SAP 701) | 30 |

Or alternative: gate on `sap_main_heating_code in {191, 401-409, 421-425, 515, 691, 694, 701}` and infer electric — broader pattern.

### 4. solid fuel 2 / 3 PE residuals (-935 to -1211)

After R-dispatch closed 7/10 solid-fuel PE residuals, 2 remain at
~-1000 PE. Both are anthracite (codes 158, 160). Same fuel and same R
as other variants that closed. Possible:

- Table 4a efficiency variant (winter/summer split)
- Secondary heating fraction (Table 11) not applying

### 5. pcdb 1 PE residual −3135

Oil PCDB-listed boiler cert (no SAP code, PCDB index drives lookup).
Largest open PE residual. Separate cause from R-dispatch.

### 6. Tariff-dependent R promotion

Codes 402/403/405 have R=0.20/0.40 off-peak vs R=0.40/0.60 24-hour
tariff per Table 4a. Current dict uses off-peak default (corpus is all
off-peak). If a 24-hour cert ever surfaces, promote
`_RESPONSIVENESS_BY_SAP_CODE` from `dict[int, float]` to
`dict[(int, Tariff), float]` lookup.

### 7. Latent strict-raise opportunity

`table_32.is_electric_fuel_code` / `_is_gas_code` silently return False
for unmapped fuel codes. User raised this in S0380.136 discussion as a
follow-up forcing-function pattern (same shape as
`MissingMainFuelType`). Broad blast radius — defer until after the
visible-residual closures.

## 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`
  - **Spec line 15271** (R = responsiveness ... Table 4a or Table 4d)
  - **Table 4a** (p.163-170) — heating systems with R column
  - **Table 4b** (p.170-171) — gas / liquid fuel boilers
  - **Table 4d** (p.170) — heat emitter R
  - **Table 4e** (p.171-174) — control codes
  - **Table 9 / 9a / 9b** — heating duration + MIT formulas (where R
    enters the MIT adjustment)
  - **Table 12** (p.191) — SAP rating fuel prices (regulated tariff)
  - **Table 12a** — high/low-rate fraction by system × tariff
- **RdSAP 10 spec**: `RdSAP 10 Specification 10-06-2025.pdf`
  - **§19 Table 32** (p.95) — RdSAP10 fuel prices / CO2 / PE
  - Heating oil price 7.64 in spec but 5.44 empirically (per S0380.131)
- **BRE technical papers** at `sap10 technical papers/` — no Table 32
  errata
- **SAP 10.3** at `sap-10-3-full-specification-2026-01-13.pdf`:
  **DO NOT reference** (per [[feedback-sap-10-2-only-never-10-3]])

## Workflow per slice

1. Read spec page + identify rule
2. Probe cascade vs worksheet line-by-line for one variant in the
   cluster; verify the diagnosis closes the residual via monkey-patch
3. Write failing AAA test (literal `# Arrange / # Act / # Assert`)
4. Implement helper / dispatch entry / mapper extension
5. Verify test passes
6. Probe full cluster impact + re-pin affected variants
7. Run extended handover suite (command above)
8. Pyright net-zero check on touched files (`git stash` → pyright →
   `git stash pop` → pyright)
9. Commit with spec citation +
   `Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>`
10. Update `project-heating-systems-corpus` + `MEMORY.md` index

## What NOT to do

- **Don't reference SAP 10.3** — track 10.2 deliberately
- **Don't widen pin tolerances** to make pins pass — re-pin smaller or
  find the spec gap
- **Don't re-investigate closed work** (Slices .91..137 all settled)
- **Don't add new helpers to `domain/sap10_ml/`** — on the deprecation
  path
- **Don't conflate the R-dispatch with the cost cluster** — R closes PE
  (via demand), the +5..+9 SAP residual on electrics is the *cost-side*
  gap, a separate issue
- **Don't accept "spec-precision floor" framing** without spec-citation
  work — verify against worksheet PDF + cross-cert empirical evidence

## User direction at end of session

The conversation flowed:
1. Started on solid fuel 8 +0.87 ΔSAP — discovered it was a compensating-
   errors illusion (real CO2 Δ +3525)
2. User: "could we add an exception in the calculator that an empty
   fuel type can't be given?" → S0380.132 strict-raise
3. User: "I'm okay with breaking the tests if that means not debugging
   silent, incorrect fallbacks"
4. Suggested SAP-code → fuel derivation → S0380.133 solid-fuel EES
   dispatch
5. User asked for audit of remaining patterns → found PE measurement
   bug + per-cluster issues → S0380.134 (PE pin fix) → S0380.135 (R
   dispatch solid fuel)
6. User: "is this another opportunity to raise an exception?" during
   S0380.136 — answered: this is a *different bug class*
   (type ambiguity, not missing data); broader raise opportunity exists
   for `is_electric_fuel_code` / `_is_gas_code` silent-False on
   unmapped (catalogued as #7 above)
7. S0380.137 extended R-dispatch to electric

The "find ONE fix that closes MULTIPLE variants" framing is the user's
preferred approach. Each slice closed 6-10 variants via a single
table-dispatch or convention-routing change.

Good luck.