diff --git a/backend/documents_parser/elmhurst_extractor.py b/backend/documents_parser/elmhurst_extractor.py
index 822254ca..a3449014 100644
--- a/backend/documents_parser/elmhurst_extractor.py
+++ b/backend/documents_parser/elmhurst_extractor.py
@@ -417,8 +417,14 @@ class ElmhurstSiteNotesExtractor:
             )
         return windows
 
-    # Anchors used by the layout-style window parser.
-    _WIDTH_HEIGHT_AREA_RE = re.compile(r"^(\d+\.\d+)\s+(\d+\.\d+)\s+(\d+\.\d+)$")
+    # Anchors used by the layout-style window parser. The W/H/Area anchor
+    # is sometimes followed by a joined glazing-type phrase on the same
+    # line (e.g. '1.22 1.76 2.15 Double pre 2002'); the optional 4th
+    # capture surfaces that text so the parser can use it instead of a
+    # separately-laid-out prefix line.
+    _WIDTH_HEIGHT_AREA_RE = re.compile(
+        r"^(\d+\.\d+)\s+(\d+\.\d+)\s+(\d+\.\d+)(?:\s+(\S.*?))?$"
+    )
     _MANUFACTURER_RE = re.compile(r"^(Manufacturer|Default)\s+(\d+\.\d+)$")
     _ORIENTATION_TOKENS = frozenset({
         "North", "South", "East", "West", "NE", "NW", "SE", "SW",
@@ -507,6 +513,28 @@ class ElmhurstSiteNotesExtractor:
                 return j
         return None
 
+    _FRAME_TYPE_AND_FACTOR_RE = re.compile(r"^(\S+(?:\s+\S+)*?)\s+(\d\.\d+)$")
+
+    def _parse_frame_type_and_factor(
+        self, lines: List[str], data_idx: int
+    ) -> tuple[str, Optional[float], int]:
+        """Return `(frame_type, frame_factor, middle_start_idx)` from
+        the lines immediately after the data anchor. Layout-style cell
+        joining can collapse what's normally two lines ('PVC' then
+        '0.70') into one ('Wood 0.70'); both shapes need to feed the
+        same downstream slice."""
+        combined = self._FRAME_TYPE_AND_FACTOR_RE.match(lines[data_idx + 1].strip())
+        if combined is not None:
+            return combined.group(1), float(combined.group(2)), data_idx + 2
+        if data_idx + 2 >= len(lines):
+            return lines[data_idx + 1].strip(), None, data_idx + 2
+        frame_type = lines[data_idx + 1].strip()
+        try:
+            frame_factor = float(lines[data_idx + 2].strip())
+        except ValueError:
+            return frame_type, None, data_idx + 3
+        return frame_type, frame_factor, data_idx + 3
+
     def _partition_after_manuf(
         self, lines: List[str], manuf_idx: int, next_data_idx: int
     ) -> int:
@@ -514,14 +542,25 @@ class ElmhurstSiteNotesExtractor:
         block (and the inclusive lower bound for the next window's prefix
         block). After the manufacturer line come 3 fixed tokens (g_value,
         draught, shutters); the variable suffix lines start at manuf+4
-        and run until the next window's glazing-type-start token (e.g.
-        'Double between 2002', 'Single', 'Triple ...') or until the
-        next window's data line if no such token is present."""
+        and run until either (a) the next window's glazing-type-start
+        token (e.g. 'Double between 2002', 'Single', 'Triple ...') or
+        (b) the second orientation token in the gap, whichever comes
+        first. Branch (b) covers layouts where the glazing-type is
+        joined to the data line (no separate prefix line exists), so
+        the only signal of window-transition is the orientation tokens
+        rotating: orient_suffix(k) → orient_prefix(k+1). Falls through
+        to `next_data_idx` when neither marker is present."""
         scan_start = manuf_idx + 4
+        seen_orient = False
         for j in range(scan_start, next_data_idx):
-            first_word = lines[j].strip().split(" ", 1)[0]
+            stripped = lines[j].strip()
+            first_word = stripped.split(" ", 1)[0]
             if first_word in self._GLAZING_TYPE_PREFIX_WORDS:
                 return j
+            if stripped in self._ORIENTATION_TOKENS:
+                if seen_orient:
+                    return j
+                seen_orient = True
         return next_data_idx
 
     def _parse_window_from_anchors(
@@ -537,20 +576,28 @@ class ElmhurstSiteNotesExtractor:
         width = float(anchor.group(1))
         height = float(anchor.group(2))
         area = float(anchor.group(3))
+        # Layout-style cell joining sometimes leaves the glazing-type
+        # phrase trailing the W H Area triplet on the same line (e.g.
+        # "1.22 1.76 2.15 Double pre 2002"); when present we pass it
+        # through as `inline_glazing_type` and the composer skips the
+        # would-be glazing-prefix scan.
+        inline_glazing_type = anchor.group(4) if anchor.lastindex and anchor.lastindex >= 4 else None
 
         # frame_type and frame_factor immediately follow the data line.
-        if data_idx + 2 >= len(lines):
+        # Layout-style cell joining sometimes collapses them onto a
+        # single "Wood 0.70" line; treat both shapes uniformly so the
+        # downstream `middle` slice still starts at the first variable
+        # field (glazing_gap / bp / location / orient).
+        if data_idx + 1 >= len(lines):
             return None
-        frame_type = lines[data_idx + 1].strip()
-        try:
-            frame_factor = float(lines[data_idx + 2].strip())
-        except ValueError:
-            return None
-        if not 0.0 < frame_factor <= 1.0:
+        frame_type, frame_factor, middle_start = self._parse_frame_type_and_factor(
+            lines, data_idx
+        )
+        if frame_factor is None or not 0.0 < frame_factor <= 1.0:
             return None
 
         # Variable-order tokens between frame_factor and Manufacturer.
-        middle = [lines[j].strip() for j in range(data_idx + 3, manuf_idx)]
+        middle = [lines[j].strip() for j in range(middle_start, manuf_idx)]
         glazing_gap = next((t for t in middle if "mm" in t.lower()), None)
         location = next((t for t in middle if "wall" in t.lower()), "External wall")
         bp_inline = next((t for t in middle if t in self._BP_INLINE_TOKENS), None)
@@ -586,6 +633,7 @@ class ElmhurstSiteNotesExtractor:
             after=after,
             bp_inline=bp_inline,
             orient_inline=orient_inline,
+            inline_glazing_type=inline_glazing_type,
         )
 
         return Window(
@@ -613,6 +661,7 @@ class ElmhurstSiteNotesExtractor:
         after: List[str],
         bp_inline: Optional[str],
         orient_inline: Optional[str],
+        inline_glazing_type: Optional[str] = None,
     ) -> tuple[str, str, str]:
         """Re-join the glazing-type / building-part / orientation tokens
         split by the layout preprocessor. Each is at most 2 fragments
@@ -645,8 +694,13 @@ class ElmhurstSiteNotesExtractor:
         bp_prefix_frag = pop_if_bp_fragment(prefix)
         bp_suffix_frag = pop_if_bp_fragment(suffix)
 
-        # Glazing type: remaining prefix + remaining suffix (joined).
-        glazing_type = " ".join([*prefix, *suffix]).strip()
+        # Glazing type: an inline glazing-type captured from the data
+        # line (layout-joined variant) wins; otherwise join the remaining
+        # prefix + suffix fragments.
+        if inline_glazing_type is not None:
+            glazing_type = inline_glazing_type
+        else:
+            glazing_type = " ".join([*prefix, *suffix]).strip()
 
         # Building part: inline token wins; otherwise join prefix + suffix.
         if bp_inline is not None:
diff --git a/backend/documents_parser/tests/fixtures/Summary_000477.pdf b/backend/documents_parser/tests/fixtures/Summary_000477.pdf
new file mode 100644
index 00000000..94ca3002
Binary files /dev/null and b/backend/documents_parser/tests/fixtures/Summary_000477.pdf differ
diff --git a/backend/documents_parser/tests/fixtures/Summary_000480.pdf b/backend/documents_parser/tests/fixtures/Summary_000480.pdf
new file mode 100644
index 00000000..f0cc3875
Binary files /dev/null and b/backend/documents_parser/tests/fixtures/Summary_000480.pdf differ
diff --git a/backend/documents_parser/tests/fixtures/Summary_000487.pdf b/backend/documents_parser/tests/fixtures/Summary_000487.pdf
new file mode 100644
index 00000000..9afae0e4
Binary files /dev/null and b/backend/documents_parser/tests/fixtures/Summary_000487.pdf differ
diff --git a/backend/documents_parser/tests/fixtures/Summary_000490.pdf b/backend/documents_parser/tests/fixtures/Summary_000490.pdf
new file mode 100644
index 00000000..9303bfe6
Binary files /dev/null and b/backend/documents_parser/tests/fixtures/Summary_000490.pdf differ
diff --git a/backend/documents_parser/tests/fixtures/Summary_000516.pdf b/backend/documents_parser/tests/fixtures/Summary_000516.pdf
new file mode 100644
index 00000000..60c73055
Binary files /dev/null and b/backend/documents_parser/tests/fixtures/Summary_000516.pdf differ
diff --git a/docs/sap-spec/NEXT_AGENT_PROMPT.md b/docs/sap-spec/NEXT_AGENT_PROMPT.md
index ebca5762..266fe437 100644
--- a/docs/sap-spec/NEXT_AGENT_PROMPT.md
+++ b/docs/sap-spec/NEXT_AGENT_PROMPT.md
@@ -1,245 +1,139 @@
-# Handover — close the Elmhurst Summary→SAP chain to 1e-4
+# Handover — close the remaining 5 Elmhurst Summary→SAP chains to 1e-4
 
 You are picking up branch `ara-backend-design-prd` mid-stream. The
-previous agent left a near-complete but **not actually complete**
-validation chain. This handover is honest about what's done, what's
-still wrong, and why a fresh approach may help.
+previous chain of work closed **Summary_000474** to 1e-4 (Slice 47)
+and landed extractor infrastructure that helps the other 5 fixtures
+(Slice 48), but each of the 5 remaining certs still has its own diff
+to close. This handover captures the exact per-cert state so you
+don't have to rediscover it.
 
 ## The 30-second picture
 
-There are two paths into the calculator:
-
 ```
-Path A:  hand-built EpcPropertyData  →  cascade  →  SAP 62.2584  ← matches Elmhurst worksheet PDF to 4 d.p.  ✓
-Path B:  Summary_NNNNNN.pdf  →  extractor  →  ElmhurstSiteNotes
-                            →  from_elmhurst_site_notes  →  EpcPropertyData
-                            →  cascade  →  SAP 62.5195  ← off by 0.2611 unrounded SAP points  ✗
+Cert     Mapped SAP   Target SAP   Δ          Notes
+000474   62.2584      62.2584      0.0000  ✓  CLOSED (Slice 47)
+000477   71.3712      65.0057     +6.3655     secondary heating + lighting
+000480   69.5681      61.2986     +8.2695     unknown (largest gap)
+000487   69.7864      61.6431     +8.1433     window count 1/many (extractor) + others
+000490   63.0530      57.3979     +5.6551     unknown
+000516   68.7749      62.7937     +5.9812     roof window separation
 ```
 
-Both paths feed the same calculator (`calculate_sap_from_inputs`). Path
-A proves the cascade is provably equivalent to Elmhurst's calculator
-(`sap_score_continuous` = 62.2584 matches Elmhurst worksheet PDF line
-257 exactly). Path B uses `from_elmhurst_site_notes` instead of the
-hand-built fixture; **it should produce identical output**, because
-the Summary PDF and the hand-built fixture encode the same source-of-
-truth data. It doesn't. The 0.26 SAP gap means information is being
-dropped in the extractor or mapper.
+All Δ are positive — the mapper is computing SAP too HIGH, which
+typically means missing cost contributions (secondary heating fuel,
+lighting, etc.) or under-counted heat-loss area.
 
-The user explicitly rejected "within 0.5 is good enough" — the chain
-must reproduce Elmhurst to `1e-4` like every other Elmhurst worksheet
-test.
+Forcing function for the 000474 case is in:
+`backend/documents_parser/tests/test_summary_pdf_mapper_chain.py::test_summary_000474_full_chain_sap_matches_worksheet_pdf_exactly`
+(green at 1e-4). When you close each remaining cert, add a mirror
+test next to it.
 
-The end goal is: `api → EpcPropertyData → Sap10 calculator` with
-`< 0.5` SAP error (the API publishes rounded SAP integers, so half a
-point is rounding noise). But for the Elmhurst-site-notes path,
-because Elmhurst's worksheet PDFs publish unrounded line-ref values,
-the target is **zero error to 1e-4**.
+## What landed already
 
-## Forcing function
-
-There is one failing test pinning this:
-
-```
-backend/documents_parser/tests/test_summary_pdf_mapper_chain.py::
-  test_summary_000474_full_chain_sap_matches_worksheet_pdf_exactly
-```
-
-It asserts `abs(mapped_sap - 62.2584) < 1e-4` and currently fails with
-`Δ = 0.2611`. Your job is to drive it to GREEN.
-
-## Definition of done
-
-- The failing test above passes at `1e-4` tolerance.
-- The two other `test_summary_pdf_mapper_chain.py` tests stay green
-  (`sap_building_parts == 3`, `sap_windows == 7`).
-- The wider `datatypes/epc/` + `backend/documents_parser/tests/`
-  regression stays green (the 9 pre-existing `test_appendix_u.py`
-  failures and 1 pre-existing 1e-9 FEE-precision failure are
-  unrelated — leave them).
-- Once 000474 is at 1e-4, replicate the test for the other 5 Summary
-  PDFs (000477, 000480, 000487, 000490, 000516) — files are under
-  `sap worksheets/` at the repo root, **untracked**, copy each into
-  `backend/documents_parser/tests/fixtures/` as you go.
-- For each cert, pin against the unrounded SAP value lodged in line
-  257 of the corresponding `U985-0001-NNNNNN.pdf` worksheet.
-
-## What the previous agent did right
-
-12 commits across the session. The architecturally-load-bearing ones:
-
-| Slice | Commit | Effect |
+| Slice | Commit | What |
 |---|---|---|
-| 44 | `ea6d4263` | flat_roof_insulation_thickness mapper passthrough |
-| 45a/b/c | `f08252dc` / `24f35f8b` / `5acbecc5` | PV cascade per Appendix M + U (orientation × pitch × Table-M1 ZPV × rating-vs-demand climate) |
-| audit pins | `15789f5a` / `acc6331d` / `8ac548ca` | u_wall / u_roof / u_floor description-cascade pins against Tables 6 / 16 / §5.12 — proves U-value cascade is spec-correct on the cohort |
-| 46 scaffold | `ccf7aa21` | First scaffold test for Summary→EpcPropertyData chain (strict-xfail) |
-| 46a | `36f2c7bb` | Multi-bp support: schema adds `ExtensionPart`; extractor parses Main + 1st Extension + 2nd Extension subsections in §4/§7/§8/§9 with "As Main: Yes" inheritance; mapper produces a `SapBuildingPart` per bp |
-| 46b | `066dce19` | Layout-style window parser anchored on `W H Area` data line + `Manufacturer <U>` line — extracts 7 windows from the Summary table layout |
-| **46c** | **`256a5afe`** | **String→int code translations for every Elmhurst-coded field the cascade reads (age band, wall_construction, wall_insulation_type, main_fuel_type, heat_emitter_type, main_heating_control, orientation); PCDB index parsed from `pcdf_boiler_reference`; floor ordering + 0.25 m upper-storey adjustment + `is_exposed_floor` flag for "above unheated space"** |
+| 47 | `29ab80b0` | `main_heating_category=2` in mapper → pumps_fans 130→160; window-gap partitioned on glazing-type-start marker → fixes W4/W5 orientation mis-classification |
+| 48 | (this slice) | Extractor handles combined `Wood 0.70` frame line; data anchor allows trailing glazing-type (`1.22 1.76 2.15 Double pre 2002`); partition falls back to second-orient-token when no glazing marker in gap; 5 fixture PDFs copied to `backend/documents_parser/tests/fixtures/` |
 
-After 46c, mapped SAP is 62.52 vs target 62.26 (`Δ = 0.26`).
+## Per-cert diff diagnoses (already done — don't re-discover)
 
-## What the previous agent got wrong
+### 000477 — Δ +6.37 — single-BP cert
+Run `python /tmp/diff_cert.py 000477` to reproduce. Scalar input diffs:
+- `secondary_heating_fraction`: mapped=**0.0** vs handbuilt=**0.1** ← root cause. Handbuilt has `secondary_heating_type=691` (Electric panel heaters) lodged on `SapHeating`. Mapper doesn't extract from §10 "Secondary heating" Summary PDF section.
+- `lighting_kwh_per_yr`: mapped=160.88 vs handbuilt=201.68 — bulb count mismatch
+- `secondary_heating_co2_factor_kg_per_kwh`, `secondary_heating_primary_factor`: None vs populated — downstream of the missing secondary_heating_type
 
-**Overclaimed completion at the 0.5-tolerance milestone.** The
-original test was written with a 0.5 tolerance (mirroring the
-API-cert residual cohort, where the API publishes rounded SAP
-integers so half a point is just rounding). That's the wrong
-tolerance for the Elmhurst path: Elmhurst lodges full PDF lines with
-4-d.p. unrounded values, and our cascade matches them exactly on
-hand-built inputs. The bar is `1e-4`, not 0.5. The previous agent
-committed Slice 46c with a 0.5-tolerance pin; this handover has
-since tightened it to `1e-4` (the failing test above).
+**Fix**: Extend `ElmhurstSiteNotesExtractor` to extract §10 Secondary heating fields, and `_map_elmhurst_sap_heating` to populate `secondary_heating_type` + `secondary_fuel_type` on the `SapHeating`.
 
-## The remaining diffs (Slice 46c → 1e-4 SAP)
+### 000487 — Δ +8.14 — only 1 window extracted (should be many)
+Despite Slice 48's frame-line + data-anchor improvements, the §11
+table layout of this cert still drops most windows. Run
+`python /tmp/dump_one.py 000487` to see the parsed window. Inspect
+the raw layout via `python /tmp/dump_section.py 000487` — the table
+has a different cell-joining pattern that the current parser hasn't
+yet covered.
 
-After Slice 46c, the only differing `cert_to_inputs(epc)` scalar
-fields between mapped and hand-built are:
+### 000516 — Δ +5.98 — roof window contamination
+6 vertical windows extracted (correct: 5) — the 6th is actually a
+**roof window** (`1.05×1.12=1.18 m² U=3.10 NE`, pitch 45°) being
+treated as vertical. Handbuilt 000516 separates this into
+`sap_roof_windows=[SapRoofWindow(area_m2=1.18, u_value_raw=3.40,
+orientation=2 NE, pitch_deg=45.0, ...)]`.
 
-```
-hot_water_kwh_per_yr:      mapped=2291.7821223353485   handbuilt=2291.7784230242883   (Δ < 0.01 — float drift)
-pumps_fans_kwh_per_yr:     mapped=130.0                handbuilt=160.0                ← 30 kWh, real bug
-lighting_kwh_per_yr:       mapped=139.94522455112704   handbuilt=139.94522455112707   (Δ < 1e-10 — float noise)
-pumps_fans_primary_factor: mapped=1.5128000000000001   handbuilt=1.5128               (float repr — harmless)
-fabric_energy_efficiency_kwh_per_m2_yr: mapped=186.62  handbuilt=186.88               (output, not input — driven by solar gains)
-```
+**Fix**: Add roof-window extraction in `ElmhurstSiteNotesExtractor`
+(likely a "Roof Windows" subsection of §11). Map to `SapRoofWindow`
+not `SapWindow`.
 
-Plus a window-orientation mis-classification (see below).
+### 000480 — Δ +8.27 — diagnosis pending
+Run `python /tmp/diff_cert.py 000480` to start. Two BPs (Main + ext)
+extracted correctly, 7 windows extracted. Largest gap of the 5 — may
+have multiple compounding issues.
 
-### Diff #1: `pumps_fans_kwh_per_yr` = 130 vs 160 (30 kWh)
+### 000490 — Δ +5.66 — diagnosis pending
+Same: `python /tmp/diff_cert.py 000490`.
 
-This is the dominant residual contributor. Search `cert_to_inputs.py`
-for `pumps_fans_kwh_per_yr` to find what drives it. Likely candidates:
-- `central_heating_pump_age` (the Summary PDF lodges "Heat pump age:
-  Unknown" but that's the HEAT pump, not the central heating pump —
-  may need a separate field on `ElmhurstSiteNotes.MainHeating`)
-- Boiler type / FGHRs / weather compensator flags
-- Some specific Table 4d/4e cascade input we're dropping
-
-The cascade reads `MainHeatingDetail.central_heating_pump_age: Optional[int]`
-which the Elmhurst mapper doesn't currently populate.
-
-### Diff #2: Window [4] orientation mis-classified as SE (4) — should be E (3)
-
-Mapped windows:
-```
-  [4] orient=4 (SE)  W=1.1  H=1.6  U=2.0
-```
-
-Hand-built has TWO East U=2.0 windows totalling 3.74 m² area. Mapped's
-window [2] (East, 1.98 m²) + window [4] (mis-labelled SE, 1.76 m²) =
-3.74 m² ✓ — exactly matches. So the layout-style window parser is
-producing `orientation='East-South'` for window [4] when it should be
-just `'East'`. Look at `_compose_window_descriptors` in
-`backend/documents_parser/elmhurst_extractor.py` — the suffix
-token "South" is being joined with the inline "East" prefix when it
-shouldn't be (probably the "South" belongs to a different window).
-
-The window count itself also differs: mapped extracts 7 individual
-windows, hand-built consolidates to 5 by `(orientation, U)` group with
-width = total area / 1.0 m. Both should be functionally equivalent
-to the cascade IF orientations + U-values + total areas all match. So
-fixing the orientation should close this gap.
-
-### Diff #3: float-precision noise
-
-`hot_water_kwh_per_yr` (sub-0.01 kWh) and `lighting_kwh_per_yr`
-(sub-1e-10 kWh) are downstream of accumulation order in the cascade.
-`pumps_fans_primary_factor` 1.5128000000000001 vs 1.5128 is a Python
-float repr quirk. These won't close the SAP gap; ignore them unless
-the other fixes leave the test slightly red and one of these turns
-out to be the last decimal.
-
-## Why a fresh approach may help
-
-The previous agent's pattern was "fix one bug at a time, ship when
-test passes loosely." The right pattern for `1e-4` is the opposite:
-**systematically diff every input field between mapped and hand-built,
-fix every diff, then run the test once.** That's two more slices
-(pumps_fans + window orientation) — not enough for a session of
-incremental shipping, so consider doing both in one slice with the
-pin as the forcing function.
-
-You may also want to look harder at the *architectural* question:
-why does Elmhurst's "site notes" (the surveyor's input form) need to
-go through THREE schemas — `ElmhurstSiteNotes`, then `EpcPropertyData`,
-then `CalculatorInputs` — when the hand-built fixture skips straight
-to the middle one? The string→int translations in `from_elmhurst_site_notes`
-are essentially doing what the extractor should do (or what an
-`elmhurst_codes.py` codes-module could express). If `ElmhurstSiteNotes`
-stored integer codes alongside the human-readable strings, the mapper
-would be a pure projection.
-
-## Quick-orient commands
+## Probe scripts (already in `/tmp`)
 
 ```bash
-# Failing test (Δ = 0.26 SAP → target < 1e-4)
-python -m pytest backend/documents_parser/tests/test_summary_pdf_mapper_chain.py::test_summary_000474_full_chain_sap_matches_worksheet_pdf_exactly --no-cov --no-header --tb=short
+# Probe all 6 fixtures' SAP delta
+python /tmp/probe_all.py
 
-# All Summary→chain tests (2/3 green, 1 failing — the one above)
-python -m pytest backend/documents_parser/tests/test_summary_pdf_mapper_chain.py --no-cov --no-header -v
+# Dump raw extracted windows for a cert
+python /tmp/dump_one.py 000516
 
-# Wider regression to confirm no fresh breakage
-python -m pytest datatypes/epc/ backend/documents_parser/tests/ --no-cov --no-header -q
+# Dump the §11 Windows section layout (debug extractor)
+python /tmp/dump_section.py 000487
+
+# Field-by-field input diff mapped vs handbuilt
+python /tmp/diff_cert.py 000477
 ```
 
-The 9 `test_appendix_u.py` failures and 1 `test_no_ac_cert_round_trips_fee_equals_space_heating_per_m2`
-failure are **pre-existing** from before this session — don't try to
-fix them as part of this work.
+If `/tmp` got wiped, the contents are:
+- `probe_all.py`: iterates 6 fixtures, mapper-cascades each, prints
+  Δ and BPs/windows counts.
+- `dump_one.py <cert>`: prints raw `ElmhurstSiteNotes.windows` for
+  the given cert.
+- `dump_section.py <cert>`: prints the line-by-line `§11 Windows`
+  section from the layout-preprocessed pages.
+- `diff_cert.py <cert>`: cascades both mapped and handbuilt EPCs
+  through `cert_to_inputs`, diffs the scalar input fields.
+
+## Suggested next slices
+
+| Slice | Cert | Effort | Why next |
+|---|---|---|---|
+| 49 | 000477 | Medium | 1 BP topology → smallest moving parts; secondary-heating extraction unlocks the largest single fix |
+| 50 | 000516 | Medium | Roof-window separation — adds new schema field, generalisable |
+| 51 | 000487 | High | Extractor parser improvements (the §11 layout is uncovered terrain) |
+| 52 | 000490 | Unknown | Diagnose then close |
+| 53 | 000480 | Unknown | Largest Δ; do last after others reveal patterns |
+
+## Definition of done (unchanged from before)
+
+- All 6 `test_summary_pdf_mapper_chain.py` chain tests pin at 1e-4.
+- Wider regression stays green (currently 754 pass).
+- Pyright net-zero on every commit (strict mode).
+- One slice = one commit.
+- No widening, no xfail (project memory `feedback_zero_error_strict`).
 
 ## Reference materials
 
-- **`docs/sap-spec/HANDOVER_NEXT.md`** — original calculator-closure
-  handover; still useful as the canonical reference for cascade
-  conventions (AAA tests, 1e-4 tolerance, etc.).
-- **`docs/sap-spec/SAP_CALCULATOR.md`** — public API + two-cascade
-  architecture (rating vs demand).
-- **`sap worksheets/Summary_000474.pdf`** (untracked) — the source-of-
-  truth input for fixture 000474. Mirror tracked at
-  `backend/documents_parser/tests/fixtures/Summary_000474.pdf`.
-- **`sap worksheets/U985-0001-000474.pdf`** (untracked) — the
-  Elmhurst-computed worksheet with line refs the test pins against
-  (line 257 for unrounded SAP).
-- **`packages/domain/src/domain/sap/worksheet/tests/_elmhurst_worksheet_000474.py`**
-  — the hand-built `EpcPropertyData` for the same fixture. The CALCULATOR-
-  EQUIVALENT target the mapper must reproduce.
-
-## File map for the work ahead
-
-| File | Role |
-|---|---|
-| `backend/documents_parser/elmhurst_extractor.py` | PDF → `ElmhurstSiteNotes` extractor; layout-style window parser at `_compose_window_descriptors` is where diff #2 lives |
-| `datatypes/epc/surveys/elmhurst_site_notes.py` | The schema (recently extended with `ExtensionPart`); `MainHeating` may need a `central_heating_pump_age` field for diff #1 |
-| `datatypes/epc/domain/mapper.py:254-326` | `from_elmhurst_site_notes` — the mapper itself |
-| `datatypes/epc/domain/mapper.py:1772-1830` | Code-translation helpers (`_leading_code`, `_elmhurst_wall_construction_int`, etc.) |
-| `datatypes/epc/domain/mapper.py:2010-2080` | `_map_elmhurst_building_part` + extension iteration |
-| `datatypes/epc/domain/mapper.py:2180+` | `_map_elmhurst_sap_heating` — likely where diff #1 (pumps_fans) is fixed |
-| `packages/domain/src/domain/sap/rdsap/cert_to_inputs.py` | Cascade — search `pumps_fans_kwh_per_yr` for diff #1's root cause |
-
-## Conventions you must honour (from project memory)
-
-- AAA test convention: every new test uses literal `# Arrange / # Act
-  / # Assert` headers
-- `abs(diff) <= tol` not `pytest.approx` (strict pyright)
-- One slice = one commit; stage by name (`?? non_invasive_photos/` and
-  similar untracked junk must not be staged)
-- 1e-4 tolerance, no widening, no xfail (`feedback_zero_error_strict`)
-- Strict pyright net-zero on every commit
+- `docs/sap-spec/HANDOVER_NEXT.md` — original cascade-conventions handover.
+- `docs/sap-spec/SAP_CALCULATOR.md` — public API + two-cascade architecture.
+- Hand-built worksheet fixtures: `packages/domain/src/domain/sap/worksheet/tests/_elmhurst_worksheet_*.py` — the calculator-equivalent EpcPropertyData each mapped chain must reproduce.
+- Untracked source PDFs: `sap worksheets/` (`Summary_NNNNNN.pdf` + `U985-0001-NNNNNN.pdf` worksheets — the unrounded SAP target lives next to "SAP value" in the U985 PDF).
 
 ## Branch state at handover
 
 ```
-$ git log --oneline -5
-256a5afe Slice 46c: Elmhurst mapper produces calculator-equivalent EpcPropertyData — Summary_000474 SAP within 0.5 of worksheet PDF
-066dce19 Slice 46b: Elmhurst extractor parses windows from layout-style Summary PDFs
-36f2c7bb Slice 46a: Elmhurst mapper handles multi-bp Summary PDFs — Summary_000474 chain test flips green
-ccf7aa21 Scaffold: end-to-end Summary→EpcPropertyData chain test for 000474 (xfail)
-8ac548ca Audit: pin u_floor §5.12 formula cascade for cert 0240 cohort geometry
+$ git log --oneline -7
+<this commit>  Slice 48: Elmhurst extractor handles 5 new layout quirks; 5 fixture PDFs added
+29ab80b0       Slice 47: Summary_000474 chain pins SAP at 1e-4 vs worksheet PDF
+b6544e1c       Handover: tighten Summary→SAP chain pin to 1e-4 + brief next agent
+256a5afe       Slice 46c: Elmhurst mapper produces calculator-equivalent EpcPropertyData — Summary_000474 SAP within 0.5 of worksheet PDF
+066dce19       Slice 46b: Elmhurst extractor parses windows from layout-style Summary PDFs
+36f2c7bb       Slice 46a: Elmhurst mapper handles multi-bp Summary PDFs — Summary_000474 chain test flips green
+ccf7aa21       Scaffold: end-to-end Summary→EpcPropertyData chain test for 000474 (xfail)
 ```
 
-The 0.5 tolerance in commit 46c's message is stale — this handover
-tightened it to 1e-4 after the commit. The first thing you commit
-should fix one of the two diffs and explicitly mention closing the
-last bit of the gap toward 1e-4.
-
 Good luck.