docs: handover + next-agent prompt post S0380.105..109 (MEV trifecta + window routing + Connected gable + §5.7/5.8 brick formula)

Captures the 5-slice session that took cert 000565 continuous SAP from +0.0182 → -0.0059 (magnitude 67% smaller) via spec-cited intermediate-value closures. HANDOVER_POST_S0380_109.md full state + per-slice movement + per-pin journey + lessons learned NEXT_AGENT_PROMPT_POST_S0380_109.md focused briefing pointing at S0380.110 (Lighting g×FF closure — leading remaining residual at -2.17 kWh) and S0380.111 (roof window U formula refinement). Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
2026-06-08 11:17:27 +00:00 · 2026-05-30 18:16:16 +00:00 · 2026-05-30 18:16:16 +00:00 · 98a4b5b9e6
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+# Handover — post S0380.105..109 (MEV CO2/PE + window routing + Connected gable + §5.7/5.8 brick formula)
+
+Branch: `feature/per-cert-mapper-validation`. **HEAD `efb203f7`**.
+Predecessor: [`HANDOVER_POST_S0380_103.md`](HANDOVER_POST_S0380_103.md).
+
+## Slices committed this session (S0380.105..109)
+
+Five spec-cited slices targeting cert 000565 continuous-SAP closure.
+The MEV trifecta completed first (.105/.106), then a routing fix
+(.107) surfaced and re-shaped the fabric residuals, then two
+spec-correct fabric closures (.108/.109) drove the fabric residual
+from -0.99 W/K → +0.03 W/K and continuous SAP from +0.0182 → -0.0059
+(magnitude 67% smaller).
+
+| Slice | Commit | Spec | Cert 000565 outcome |
+|---|---|---|---|
+| **S0380.105** | `8a3aaf7a` | SAP 10.2 Table 12a Grid 2 + Table 12d (PDF p.191, p.194) — MEV CO2 split | `pumps_fans_co2_kg_per_yr` ✓ EXACT (35.3349 vs ws (267)). Total CO2 sign-flipped -1.81 → -2.12 (exposed downstream main_heating CO2 -2.43). |
+| **S0380.106** | `8effa2d0` | SAP 10.2 Table 12a Grid 2 + Table 12e (p.191, p.195) — MEV PE split | `pumps_fans_pe_kwh_per_yr` ✓ EXACT (383.3797 vs ws (281)). PE 62228.49 → 62227.06. MEV cascade trifecta cost/CO2/PE COMPLETE. |
+| **S0380.107** | `b7fa5f74` | RdSAP 10 §3.7.1 (PDF p.21) + §8.2 (p.50) — window/rooflight routing | New 4-rule heuristic uses BP roof type alongside glazing/U. Closes windows ✓ EXACT. Net fabric HTC -0.99 → +0.33 W/K. Continuous SAP +0.0182 → -0.0128 (magnitude 30% smaller). Integer SAP TRANSIENTLY 29→28 (crossed 28.5 rounding boundary). S0380.103 cost test reframed to pin rate not total. |
+| **S0380.108** | `9159e91f` | RdSAP 10 §3.9.2 step (d) + Table 4 row 4 (PDF p.22-23) — Connected RR gables | New `connected_wall` kind: deducts area from A_RR but skips W/K. Closes roof +1.59 → +0.30 W/K (81% closed) + TB +0.71 → +0.15 (79%) + area +4.70 → +1.02 m² (78%). **Integer SAP RECOVERED to 29 ✓ EXACT.** Continuous SAP sign-flipped under (-0.0128 → +0.0293). |
+| **S0380.109** | `efb203f7` | RdSAP 10 §5.7 Table 13 + §5.8 Table 14 (PDF p.41-42) — solid brick + insulation formula | §5.7+§5.8 chain replaces Table-6 bucket for SOLID_BRICK + lodged thickness + External/Internal insulation. Also adds Table 6 footnote (a) cap on §5.6 stone formula (only when not dry-lined). Walls -1.54 → +0.01 W/K (essentially closed). **Continuous SAP magnitude 80% improved (+0.0293 → -0.0059).** All SH-driven downstream residuals magnitude-reduced 65-80%. |
+
+**Test baseline at HEAD `efb203f7`:** **608 pass + 7 expected
+`test_sap_result_pin[000565-*]` fails**. Pyright net-zero per
+touched file across every slice.
+
+## Cert 000565 state (HEAD `efb203f7`)
+
+### Fabric subtotals — essentially closed
+
+| Component | Cascade W/K | Worksheet W/K | Δ | Status |
+|---|---:|---:|---:|---|
+| walls | 604.08 | 604.07 | **+0.01** | sub-spec float drift |
+| **party_walls** | **65.13** | 65.13 | ✓ EXACT |  |
+| **floor** | **61.67** | 61.67 | ✓ EXACT |  |
+| roof | 51.68 | 51.38 | **+0.30** | sub-spec (S0380.108 closed 81%) |
+| **windows** | **11.48** | 11.48 | ✓ EXACT | S0380.107 |
+| roof_windows | 3.15 | 3.58 | -0.43 | cascade U formula gap (see §A below) |
+| **doors** | **11.10** | 11.10 | ✓ EXACT |  |
+| thermal_bridging | 128.80 | 128.65 | +0.15 | sub-spec (S0380.108 closed 79%) |
+| total external area | 858.66 | 857.64 | +1.02 | sub-spec (S0380.108 closed 78%) |
+| **total W/K** | **937.09** | 937.06 | **+0.03** | essentially closed |
+
+### SapResult pins (HEAD `efb203f7`)
+
+| Pin | Cascade | Worksheet | Δ | Status |
+|---|---:|---:|---:|---|
+| **sap_score (int)** | **29** | 29 | **✓ EXACT** | S0380.108 |
+| sap_score_continuous | 28.5028 | 28.5087 | -0.0059 | 80% smaller than .104 baseline |
+| ecf | 5.3874 | 5.3866 | +0.0008 | 50% smaller than .104 |
+| total_fuel_cost_gbp | 4680.78 | 4680.26 | +0.52 | was -1.62 (.104) / -2.62 (.108) |
+| co2_kg_per_yr | 6448.34 | 6447.63 | +0.72 | was -1.81 (.104) |
+| space_heating_kwh_per_yr | 59020.02 | 59008.35 | +11.67 | was -27.5 (.104) |
+| main_heating_fuel_kwh_per_yr | 34717.66 | 34710.79 | +6.87 | was -16.2 (.104) |
+| **hot_water_kwh_per_yr** | 3755.03 | 3755.03 | ✓ EXACT | unchanged |
+| lighting_kwh_per_yr | 1382.67 | 1384.84 | -2.17 | rooflight g×FF default-vs-lodged drift |
+| **pumps_fans_kwh_per_yr** | **252.5159** | 252.5159 | ✓ EXACT | S0380.102 |
+| pumps_fans_co2_kg_per_yr | 35.3349 | 35.3349 | ✓ EXACT | S0380.105 |
+| pumps_fans_pe_kwh_per_yr | 383.3797 | 383.3796 | ✓ EXACT | S0380.106 |
+
+### Continuous SAP journey
+
+| Slice | Δ vs ws | Notes |
+|---|---:|---|
+| Pre-S0380.105 | +0.0182 | Post-S0380.103 baseline (MEV cost split) |
+| S0380.105 | +0.0182 | CO2 doesn't feed ECF — no continuous change |
+| S0380.106 | +0.0182 | PE doesn't feed ECF either |
+| S0380.107 | **-0.0128** | Window routing fix; 30% magnitude reduction; integer SAP transiently 28 |
+| S0380.108 | **+0.0293** | Connected gable deduction; integer SAP back to 29; sign-flipped |
+| S0380.109 | **-0.0059** | Solid brick §5.7+§5.8; 80% magnitude reduction from .108 |
+
+**Magnitude trajectory:** 0.0182 → 0.0128 → 0.0293 → **0.0059**.
+Net 67% improvement from session start.
+
+## Open work — prioritised next slices
+
+### S0380.110 — Lighting rooflight g×FF default-vs-lodged drift (low-medium leverage)
+
+**Current residual:** -2.17 kWh/yr (cascade UNDER ws). After S0380.107
+windows correctly route to sap_roof_windows, the cascade applies the
+Appendix L L2a daylight factor formula with rooflight contribution
+using `_G_LIGHT_DEFAULT = 0.80` and `_FRAME_FACTOR_DEFAULT = 0.70`
+regardless of the lodged glazing/frame on each rooflight.
+
+For cert 000565:
+- Item 2 (Ext2 NR rooflight, 1.2 m², Triple glazing PVC frame):
+  actual g×FF = 0.70 × 0.70 = 0.49 (cascade uses 0.56)
+- Item 5 (Ext4 A rooflight, 0.5 m², Double glazing Wood frame):
+  actual g×FF = 0.80 × 0.70 = 0.56 (cascade uses 0.56 ✓)
+
+Area-weighted: cascade overstates G_L by ~0.052 × 1.7 m² → DF
+slightly too low → lighting kWh slightly low.
+
+**Spec:** SAP 10.2 Appendix L L2a (PDF p.~74) — G_L numerator should
+use each window's own g_perpendicular and frame_factor, not defaults.
+
+**Fix location:** `domain/sap10_calculator/worksheet/internal_gains.py`
+function `_daylight_factor_from_cert`, the `rooflight_g_l_numerator`
+computation around line 613-618 — iterate `epc.sap_roof_windows` and
+use each one's actual `g_perpendicular` + `frame_factor` instead of
+defaults.
+
+**Expected closure:** lighting -2.17 → ~0 kWh/yr. Tiny continuous-SAP
+ripple (lighting feeds CO2/cost/PE via the Table 12 monthly factors).
+
+### S0380.111 — Roof window U formula refinement (low leverage)
+
+**Current residual:** -0.43 W/K (cascade UNDER ws). Cascade computes
+roof window effective U via `1 / (1/U_raw + 0.04)` = 1.852 for U_raw =
+2.0. Worksheet uses U_eff = 2.1062 for the same raw U.
+
+Reverse-engineered: 1/2.1062 = 0.4748; 0.5 (=1/U_raw) - 0.4748 =
+0.0252 — so the spec correction for roof windows differs from the
+vertical-window +0.04 by a factor of −0.0648.
+
+**Spec hunt:** SAP 10.2 §3.2 / Table 6c (PDF p.51). Table 6c has a
+distinct "U-value** (roof window)" column with values higher than the
+vertical-glazing column (by typically ~+0.2-0.3 W/m²K). The exact
+correction depends on the spec's definition of roof-window surface
+resistances vs vertical-window film coefficients.
+
+**Likely fix:** in `heat_transmission.py` the roof-window effective U
+should use a lookup keyed on the lodged glazing type rather than a
+flat +0.04 correction (which is the SAP10.2 §3.2 "windows" formula,
+not the rooflight one).
+
+**Expected closure:** roof_windows -0.43 → 0 W/K. HTC change +0.43
+W/K → continuous SAP -0.0015 (cascade more under). The roof_windows
+closure makes the residual SHIFT in the same direction as current
+-0.0059, so net continuous SAP slightly worse before lighting closes.
+
+### S0380.112 — Walls precision +0.01 W/K (sub-spec)
+
+Tiny float rounding artifact in BP[0] alt_wall_1 (granite + dry-line):
+cascade computes raw U=2.3405, ws displays U=2.34, A×U product diff is
+0.01 W/K. Rounding to 2 d.p. in the §5.6 dry-line path was added in
+S0380.109 — verify it fires for this case.
+
+### Deferred (unchanged from earlier handovers)
+
+- 12 gas-combi PV certs at +0.5..+1.6 PE (no worksheets)
+- 5 SAP-residual API-only certs (no worksheets)
+
+## What this session learned
+
+### Pattern: spec-correct intermediate fixes can sign-flip end-result residuals
+
+Each of S0380.107, .108, .109 shifted end-result residuals (cost,
+CO2, SH, continuous SAP) by amounts larger than the closure itself —
+because the cascade's pre-slice residuals were partially CANCELLING.
+Removing one mis-handled component exposes other residuals that were
+masked.
+
+The user's stated philosophy makes this explicit:
+> "It's okay if we temp drift away from continuous SAP, as long as we
+>  are actually fixing true problems with the intermediate values.
+>  Eventually, I expect the error of continuous SAP to be zero but
+>  that is only possible if we fix all of the sub components and
+>  remain true to spec."
+
+The trajectory bears this out: 5 slices → continuous SAP magnitude
+0.0182 → 0.0059 (67% improvement) through multiple sign-flips along
+the way.
+
+### Pattern: existing snapshot tests need updating when they pin downstream metrics
+
+S0380.103 cost test (`test_summary_000565_mev_fans_cost_uses_table_
+12a_grid_2_fans_for_mech_vent_rate`) was originally written against
+`total_fuel_cost_gbp` with a tight `< +£0.05` threshold. After
+S0380.107 broke that threshold (cascade catches up on fabric HTC and
+total cost shifts by £2+), the test was reframed to pin
+`inputs.pumps_fans_fuel_cost_gbp_per_kwh` directly — the specific
+metric S0380.103 closes, decoupled from downstream changes.
+
+Similarly, golden cert 6035 PE/CO2 pins were updated in S0380.109 per
+[[feedback-golden-residuals-near-zero]] — the cascade got closer to
+the actual EPC value, which is the intended direction.
+
+When future slices fire on a cert that's pinned with downstream
+metrics, the same pattern applies: update the pin or reframe to a
+narrower intermediate.
+
+## MEV PCDB arc — architecture summary (unchanged from .103 handover)
+
+The S0380.98..106 arc landed the entire MEV decentralised cascade
+end-to-end. Architecture in dependency order:
+
+```
+PCDB pcdb10.dat
+    ↓ ETL (etl.py, parser.py)
+Table 322 (per-fan SFP) ←→ Table 329 (per-ducting IUF)
+    ↓ runtime lookups (__init__.py)
+decentralised_mev_record(pcdb_id) + mv_in_use_factors_record(system_type)
+    ↓
+worksheet/mev.py — pure helpers
+    mev_sfp_av(fan_entries) → §2.6.4 equation (1) avg SFP
+    mev_decentralised_kwh_per_yr(sfp_av, V) → Table 4f line (230a) kWh
+    ↓
+cert_to_inputs.py
+    _mev_decentralised_kwh_per_yr_from_cert(epc)
+        reads epc.mechanical_ventilation_index_number, .wet_rooms_count,
+              .mechanical_vent_duct_type
+        invokes mev.py helpers
+    ↓
+_table_4f_additive_components(epc) adds MEV → pumps_fans_kwh_per_yr
+
+For COST (S0380.103):
+    _pumps_fans_fuel_cost_gbp_per_kwh(tariff, mev_kwh, total_pumps_fans_kwh)
+        → kWh-weighted blended rate (FANS_FOR_MECH_VENT vs ALL_OTHER_USES)
+
+For CO2 (S0380.105):
+    _pumps_fans_co2_factor_kg_per_kwh(tariff, mev_kwh, total_pumps_fans_kwh, monthly)
+        → kWh-weighted blend of FANS_FOR_MECH_VENT + ALL_OTHER_USES Table 12d factors
+
+For PE (S0380.106):
+    _pumps_fans_primary_factor(tariff, mev_kwh, total_pumps_fans_kwh, monthly)
+        → kWh-weighted blend of FANS_FOR_MECH_VENT + ALL_OTHER_USES Table 12e factors
+```
+
+All three helpers fall back to the existing ALL_OTHER_USES rate on
+STANDARD-tariff certs and no-MEV certs (cohort-safe). The MEV
+cascade trifecta is now COMPLETE for cert 000565.
+
+## How to run the baseline
+
+```bash
+PYTHONPATH=/workspaces/model python -m pytest \
+    backend/documents_parser/tests/test_summary_pdf_mapper_chain.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_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 \
+    --no-cov -q
+```
+
+Expected: **608 pass + 7 expected `test_sap_result_pin[000565-*]`
+fails**.
+
+The 7 expected fails (verbatim):
+```
+sap_score_continuous
+ecf
+total_fuel_cost_gbp
+co2_kg_per_yr
+space_heating_kwh_per_yr
+main_heating_fuel_kwh_per_yr
+lighting_kwh_per_yr
+```
+
+All driven by the residual lighting -2.17 kWh + roof window U formula
+gap -0.43 W/K + sub-spec walls float drift +0.01 W/K. The first two
+are the open S0380.110 / S0380.111 work fronts.
+
+## Files touched this session
+
+| File | Slices | Change |
+|---|---|---|
+| `domain/sap10_calculator/rdsap/cert_to_inputs.py` | .105, .106 | `_pumps_fans_co2_factor_kg_per_kwh` + `_pumps_fans_primary_factor` helpers + wire into call sites |
+| `datatypes/epc/domain/mapper.py` | .107, .108 | Survey-aware `_is_elmhurst_roof_window` predicate; `_elmhurst_bp_roof_type` helper; Connected-gable routing to new `connected_wall` kind |
+| `domain/sap10_calculator/worksheet/heat_transmission.py` | .108, .109 | `connected_wall` branch (deducts area, no W/K); pass `wall_thickness_mm` to per-BP main wall `u_wall` |
+| `domain/sap10_ml/rdsap_uvalues.py` | .109 | `_u_brick_thin_wall_age_a_to_e` (§5.7 Table 13); `_r_insulation_table_14` (§5.8 Table 14 interpolation); §5.7+§5.8 branch in `u_wall`; Table 6 footnote (a) cap on §5.6 stone (only when not dry-lined); 2 d.p. rounding on §5.6 dry-line result |
+| `domain/sap10_calculator/rdsap/tests/test_golden_fixtures.py` | .109 | Re-pin cert 6035 PE/CO2 expectations |
+| `backend/documents_parser/tests/test_summary_pdf_mapper_chain.py` | .105, .106, .107, .108, .109 | AAA tests for each slice; S0380.103 test reframed to pin cost rate directly |
+
+## Spec source quick-reference
+
+- **SAP 10.2 full specification**: `domain/sap10_calculator/docs/specs/sap-10-2-full-specification-2025-03-14.pdf`
+  - §3.2 / Table 6c (p.51) — Window/rooflight U formula — S0380.111 target
+  - §10a Table 12a Grid 2 (p.191) — Other electricity uses high-rate fraction — S0380.105, .106
+  - §10b Table 12d (p.194) — Monthly CO2 factors — S0380.105
+  - §10c Table 12e (p.195) — Monthly PE factors — S0380.106
+  - Appendix L L2a (p.~74) — Daylight factor G_L — S0380.110 target
+- **RdSAP 10 specification**: `domain/sap10_calculator/docs/specs/RdSAP 10 Specification 10-06-2025.pdf`
+  - §3.7.1 (p.21) — Window vs roof window classification — S0380.107
+  - §3.9.2 step (d) (p.23) — Connected gable area deduction — S0380.108
+  - §5.6 (p.40) + Table 12 (p.41) — Stone wall thin-wall formula — S0380.109 (cap)
+  - §5.7 (p.41) + Table 13 (p.41) — Brick wall U₀ by thickness — S0380.109
+  - §5.8 (p.41-42) + Table 14 (p.42) — Insulation R formula — S0380.109
+  - §8.2 (p.50) — Glazed walls/roof routing — S0380.107
+  - Table 4 row 4 (p.22) — Connected gable U=0 — S0380.108
+  - Table 6 footnote (a) (p.34) — §5.6 formula cap — S0380.109
+- **SAP 10.3 at** `sap-10-3-full-specification-2026-01-13.pdf`: **DO NOT reference** ([[feedback-sap-10-2-only-never-10-3]])
+
+## Memory updated this session
+
+- `project_cert_000565_recovery_state` — appended .105/.106/.107/.108/.109 closures + open-work analysis
+- `MEMORY.md` — refreshed at HEAD `efb203f7`
+
+## What NOT to do
+
+- **Don't reference SAP 10.3** ([[feedback-sap-10-2-only-never-10-3]]).
+- **Don't widen pin tolerances or xfail residual gaps**
+  ([[feedback-zero-error-strict]]). The 7 cert 000565 fails are the
+  work queue. When a slice surfaces a downstream pin that drifts (e.g.
+  the integer SAP rounding flip in S0380.107), bring it back via a
+  complementary closure in a subsequent slice (S0380.108 pattern).
+- **Don't re-investigate any closed work** (.91..109). All settled.
+- **Don't add new helpers to `domain/sap10_ml/`** — deprecation path
+  per [[project-sap10_ml-deprecation]]. New cascade helpers belong
+  under `domain/sap10_calculator/`. (S0380.109 extended existing
+  helpers in `rdsap_uvalues.py` — acceptable since the file is the
+  current authoritative wall-U-value table and a migration plan
+  hasn't yet landed for it specifically.)
+- **Don't avoid spec-correct closures because continuous SAP drifts
+  away or sign-flips** — user explicitly OK'd transient drift. Zero
+  error achievable only when every component is spec-correct.
+- **Don't pin downstream-only metrics with tight thresholds** —
+  S0380.103 cost test pattern. Pin the narrowest intermediate the
+  slice changes.
+
+## Memory hygiene
+
+After the next slice, update:
+- `project_cert_000565_recovery_state` — append slice closure +
+  refresh the open work-items table
+- `MEMORY.md` — refresh HEAD + one-line summary
+
+Good luck.
--- a/domain/sap10_calculator/docs/NEXT_AGENT_PROMPT_POST_S0380_109.md
+++ b/domain/sap10_calculator/docs/NEXT_AGENT_PROMPT_POST_S0380_109.md
@ -0,0 +1,244 @@
+# Next-agent prompt — post S0380.105..109
+
+Branch: `feature/per-cert-mapper-validation`.
+HEAD: `efb203f7`.
+
+Read these in order before any tool call:
+
+1. [`HANDOVER_POST_S0380_109.md`](HANDOVER_POST_S0380_109.md) — full state
+2. [`HANDOVER_POST_S0380_103.md`](HANDOVER_POST_S0380_103.md) — predecessor (background)
+
+Also load these memories before starting:
+
+- `project_cert_000565_recovery_state` — per-slice history + per-pin state
+- `reference_unmapped_sap_code` — calculator strict-raise pattern
+- `project_sap10_ml_deprecation` — `domain/sap10_ml/` is on the
+  deprecation path; new cascade helpers should land under
+  `domain/sap10_calculator/`
+- `feedback_sap_10_2_only_never_10_3` — **CRITICAL** — never reference
+  SAP 10.3 spec
+- `feedback_spec_citation_in_commits` — quote spec text + page in
+  commit messages
+- `feedback_verify_handover_claims` — verify spec citations + numeric
+  claims before implementing the prescribed fix
+- `feedback_zero_error_strict` — pyright net-zero per touched file
+- `feedback_commit_per_slice` — one slice = one commit
+- `feedback_aaa_test_convention` — every new test uses literal
+  `# Arrange / # Act / # Assert` headers
+- `feedback_e2e_validation_philosophy` — component pins at <1e-3;
+  SAP integer delta=0; no adaptive ceilings
+- `feedback_abs_diff_over_pytest_approx` — use `abs(x - y) <= tol`
+  instead of `pytest.approx` to keep pyright net-zero
+- `feedback_spec_floor_skepticism` — skeptical of "spec-precision
+  floor" claims; verify the spec citation against the PDF first
+- `feedback_golden_residuals_near_zero` — golden pins should be
+  re-pinned closer to zero as the cascade improves
+
+## Critical user direction
+
+The user's **primary metric is `sap_score_continuous`** (not just
+integer `sap_score`). The user has explicitly stated:
+
+> "It's okay if we temp drift away from continuous SAP, as long as we
+>  are actually fixing true problems with the intermediate values.
+>  Eventually, I expect the error of continuous SAP to be zero but
+>  that is only possible if we fix all of the sub components and
+>  remain true to spec."
+
+And:
+
+> "We should aim to get SAP continue exact, along with all sections.
+>  But we'll see."
+
+**Implication:** ship spec-correct slices even when they cause
+transient continuous-SAP drift. Sign-flips are expected and OK —
+they mean a previously-cancelling residual is now exposed.
+
+## State summary
+
+This session shipped **S0380.105..109** — five spec-cited slices.
+Trifecta-complete on MEV cascade (cost/CO2/PE), then three fabric
+closures that moved continuous SAP from +0.0182 → -0.0059 (magnitude
+67% smaller).
+
+1. **S0380.105** (`8a3aaf7a`) — MEV CO2 split via Table 12a Grid 2 +
+   Table 12d. `pumps_fans_co2` ✓ EXACT.
+2. **S0380.106** (`8effa2d0`) — MEV PE split via Table 12a Grid 2 +
+   Table 12e. `pumps_fans_pe` ✓ EXACT. MEV trifecta COMPLETE.
+3. **S0380.107** (`b7fa5f74`) — Window/rooflight routing via BP roof
+   type (RdSAP 10 §3.7.1 + §8.2). Windows ✓ EXACT. Net fabric HTC
+   -0.99 → +0.33 W/K. Continuous SAP +0.0182 → -0.0128. Integer SAP
+   transiently 28 (rounding boundary).
+4. **S0380.108** (`9159e91f`) — Connected RR gables deduct from A_RR
+   (RdSAP 10 §3.9.2 step d + Table 4 row 4). Roof/TB/area all closed
+   ~80%. **Integer SAP recovered to 29 ✓ EXACT.** Continuous SAP
+   sign-flipped to +0.0293.
+5. **S0380.109** (`efb203f7`) — Solid brick + insulation via §5.7
+   Table 13 + §5.8 Table 14. Walls -1.54 → +0.01 W/K (essentially
+   closed). **Continuous SAP magnitude 80% improved (+0.0293 →
+   -0.0059).** All SH-downstream residuals magnitude-reduced 65-80%.
+
+**Cert 000565 state at HEAD `efb203f7`:**
+
+| Pin | Cascade | Worksheet | Δ |
+|---|---:|---:|---:|
+| **sap_score (int)** | **29** | 29 | **✓ EXACT** |
+| sap_score_continuous | 28.5028 | 28.5087 | -0.0059 |
+| ecf | 5.3874 | 5.3866 | +0.0008 |
+| total_fuel_cost_gbp | 4680.78 | 4680.26 | +0.52 |
+| co2_kg_per_yr | 6448.34 | 6447.63 | +0.72 |
+| space_heating_kwh_per_yr | 59020.02 | 59008.35 | +11.67 |
+| main_heating_fuel_kwh_per_yr | 34717.66 | 34710.79 | +6.87 |
+| **pumps_fans_kwh_per_yr** | **252.5159** | 252.5159 | **✓ 0 EXACT** |
+| **hot_water_kwh_per_yr** | 3755.0288 | 3755.0288 | ✓ 0 EXACT |
+| lighting_kwh_per_yr | 1382.6657 | 1384.8353 | -2.17 |
+
+**Fabric (cascade vs ws):**
+
+| Component | Δ W/K |
+|---|---:|
+| walls | +0.01 (sub-spec float drift) |
+| roof | +0.30 |
+| windows | ✓ 0 EXACT |
+| roof_windows | -0.43 (cascade U formula gap) |
+| TB | +0.15 |
+| **total** | **+0.03** (essentially closed) |
+
+## Recommended next slice — S0380.110 § Lighting rooflight g×FF default-vs-lodged drift
+
+**Current residual:** -2.17 kWh/yr (cascade UNDER ws lighting).
+
+### Why it's now the leading residual
+
+After S0380.107 windows correctly route to sap_roof_windows, the
+cascade applies the Appendix L L2a daylight factor formula with
+rooflight contribution using `_G_LIGHT_DEFAULT = 0.80` and
+`_FRAME_FACTOR_DEFAULT = 0.70` regardless of the lodged glazing/frame
+on each rooflight (`domain/sap10_calculator/worksheet/internal_gains.py`
+function `_daylight_factor_from_cert` at lines ~613-618).
+
+For cert 000565:
+- Item 2 (Ext2 rooflight, 1.2 m², Triple PVC): actual g×FF = 0.70 × 0.70 = 0.49 (cascade uses 0.56)
+- Item 5 (Ext4 rooflight, 0.5 m², Double Wood): actual g×FF = 0.80 × 0.70 = 0.56 (cascade uses 0.56 ✓)
+
+Area-weighted cascade OVERSTATES rooflight G_L contribution by
+~0.052 × 1.7 m² → DF too low → cascade lighting kWh too low.
+
+### Spec citation target
+
+SAP 10.2 Appendix L §L2a (PDF p.~74) — the G_L numerator formula sums
+over each window with its OWN glazing-type g_perpendicular and frame
+factor, not a fixed default. Verify by reading the L2a / Table 6d
+section before implementing.
+
+### Investigation approach
+
+1. Confirm the L2a spec formula uses per-window g and FF.
+2. Probe the cascade vs worksheet for cert 000565 daylight factor:
+   ```python
+   from domain.sap10_calculator.worksheet.tests._elmhurst_worksheet_000565 import build_epc
+   from domain.sap10_calculator.worksheet.internal_gains import _daylight_factor_from_cert, OvershadingCategory
+   from domain.sap10_calculator.rdsap.cert_to_inputs import _rooflight_total_area_m2_from_cert
+   epc = build_epc()
+   rooflight_area = _rooflight_total_area_m2_from_cert(epc)
+   df = _daylight_factor_from_cert(epc, OvershadingCategory.AVERAGE, rooflight_area)
+   # cascade df ~ 1.34; ws implied df from continuous E_L ~ 1.34 + small delta
+   ```
+3. Change `_daylight_factor_from_cert` to iterate `epc.sap_roof_windows`
+   for the rooflight numerator, summing `area × g_perpendicular ×
+   frame_factor × 1.0` (Z_L = 1.0 for rooflights per Table 6d note 2).
+4. Sanity-check cohort: cohort certs that have rooflights (e.g. 000516
+   W6) lodge similar g/FF as the current defaults → minimal cohort
+   change.
+
+### Expected closure
+
+- lighting_kwh_per_yr -2.17 → ~0 kWh/yr
+- continuous SAP -0.0059 → small change (lighting feeds CO2/cost/PE
+  via Table 12 monthly factors)
+
+## Alternative next slice — S0380.111 § Roof window U formula refinement
+
+**Current residual:** -0.43 W/K (cascade UNDER ws on roof_windows).
+
+Cascade computes roof window effective U via `1 / (1/U_raw + 0.04)` =
+1.852 for U_raw = 2.0. Worksheet uses U_eff = 2.1062 for the same raw
+U. The cascade's vertical-window formula doesn't apply to rooflights
+— SAP 10.2 Table 6c has a distinct "U-value (roof window)" column.
+
+**Spec hunt:** SAP 10.2 §3.2 / Table 6c (PDF p.51) — has separate
+"U-value** (roof window)" column. The note says "Roof pitch 45°
+(unless horizontal), wooden or PVC". The Table 6c values for the
+glazing types lodged on cert 000565 rooflights (Double 2002-2021
+@ U=2.0 raw, Triple 2002-2021 @ U=2.0 raw) should give U_eff = 2.11.
+
+**Fix location:** `domain/sap10_calculator/worksheet/heat_transmission.py`
+roof window U computation — should use Table 6c roof-window column
+keyed on glazing type rather than the +0.04 vertical-window formula.
+
+**Lower leverage** than S0380.110 — closes -0.43 W/K HTC →
+~-0.0015 continuous SAP shift. The roof_windows closure makes the
+residual SHIFT in the same direction as current -0.0059, so net
+continuous SAP slightly worse before S0380.110 lighting closes.
+
+## Standard workflow per slice
+
+1. Read SAP 10.2 / RdSAP 10 spec page for the change — quote it in commit
+2. Probe current cascade output; identify exact spec-vs-cascade gap
+3. Write failing test FIRST (AAA structure)
+4. Implement helper / change
+5. Verify test passes
+6. Run full handover suite (command below)
+7. Check pyright on touched files — net-zero from baseline
+   (use `git stash` + re-run pyright to compute baseline)
+8. Commit with spec citation + verbatim quote
+9. Update relevant memory if state changed
+
+## How to run the baseline
+
+```bash
+PYTHONPATH=/workspaces/model python -m pytest \
+    backend/documents_parser/tests/test_summary_pdf_mapper_chain.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_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 \
+    --no-cov -q
+```
+
+Expected: **608 pass + 7 expected `test_sap_result_pin[000565-*]`
+fails**.
+
+After S0380.110 the lighting pin should close to ✓ EXACT (6 expected
+fails). After both .110 and .111, the remaining sub-spec residuals
+should be in a closure-ready state for the final continuous-SAP push.
+
+## What NOT to do
+
+- **Don't reference SAP 10.3** ([[feedback-sap-10-2-only-never-10-3]]).
+- **Don't widen pin tolerances or xfail residual gaps**
+  ([[feedback-zero-error-strict]]). The 7 cert 000565 fails are the
+  work queue.
+- **Don't re-investigate any closed work** (.91..109). All settled.
+- **Don't add new helpers to `domain/sap10_ml/`** — deprecation path
+  per [[project-sap10_ml-deprecation]]. New cascade helpers belong
+  under `domain/sap10_calculator/`.
+- **Don't avoid spec-correct closures because continuous SAP drifts
+  away** — user explicitly OK'd transient drift. Zero error
+  achievable only when every component is spec-correct.
+- **Don't pin downstream-only metrics with tight thresholds** — pin
+  the narrowest intermediate the slice changes.
+
+## Memory hygiene
+
+After the next slice, update:
+- `project_cert_000565_recovery_state` — append closure + open work-
+  items refresh
+- `MEMORY.md` index — refresh HEAD + one-line summary
+
+Good luck.