diff --git a/.claude/skills/expand-sap-accuracy-corpus/worklist.md b/.claude/skills/expand-sap-accuracy-corpus/worklist.md
index dbb1cea00..d5c40292c 100644
--- a/.claude/skills/expand-sap-accuracy-corpus/worklist.md
+++ b/.claude/skills/expand-sap-accuracy-corpus/worklist.md
@@ -387,30 +387,39 @@ Skip the 🚩 MVHR / 🚩 heat-pump-fuel and ⛔ sparse certs.
 - [ ] 10013924858 — SAP-17.0 · eng 81 / lodged 84
 
 # SAP-Schema-15.0 mapper validation (task a40e71c4-fd56-4a33-8677-e8643e6a5bb4)
-🔧 New schema — `from_sap_schema_15_0` added in mapper.py (PR #1531). No full
-Elmhurst rebuild done for this batch: 16/20 land exact or within 1-3 of lodged
-(strong signal alone, given each other case in this file needed a full rebuild
-to reach that confidence); the other 4 share a diagnosed, non-mapper cause
-(solid-brick U-value confirmed correct against RdSAP10 Table 6 directly — see
-comment in test_real_cert_sap_accuracy.py) so pinned without a rebuild too. All
-20 pinned as `RealCertExpectation`s.
-- [x] 🔧 100010359769 — SAP-15.0 · eng 68 (lodged 68)
-- [x] 🔧 100010359788 — SAP-15.0 · eng 72 (lodged 73)
-- [x] 🔍 100010086084 — SAP-15.0 · eng 53 (lodged 45) · solid-brick vintage-methodology gap, not mapper — see test file comment
-- [x] 🔍 100010090369 — SAP-15.0 · eng 53 (lodged 47) · ditto
-- [x] 🔍 100010074470 — SAP-15.0 · eng 46 (lodged 39) · ditto
-- [x] 🔍 100010100813 — SAP-15.0 · eng 59 (lodged 47) · ditto (largest gap, +12)
-- [x] 🔧 77179816 — SAP-15.0 · eng 76 (lodged 75)
-- [x] 🔧 10070400619 — SAP-15.0 · eng 77 (lodged 77)
-- [x] 🔧 77179820 — SAP-15.0 · eng 77 (lodged 77)
-- [x] 🔧 10070394806 — SAP-15.0 · eng 78 (lodged 77)
-- [x] 🔧 77181233 — SAP-15.0 · eng 68 (lodged 69)
-- [x] 🔧 77180626 — SAP-15.0 · eng 68 (lodged 68)
-- [x] 🔧 10070400618 — SAP-15.0 · eng 70 (lodged 69)
-- [x] 🔧 100010350459 — SAP-15.0 · eng 65 (lodged 65)
-- [x] 🔧 100010350468 — SAP-15.0 · eng 66 (lodged 66)
-- [x] 🔧 100010333531 — SAP-15.0 · eng 73 (lodged 74)
-- [x] 🔧 100010341489 — SAP-15.0 · eng 65 (lodged 64)
-- [x] 🔧 100010341491 — SAP-15.0 · eng 62 (lodged 59)
-- [x] 🔧 100010347646 — SAP-15.0 · eng 75 (lodged 75)
-- [x] 🔧 100010347637 — SAP-15.0 · eng 72 (lodged 72)
+🔧 New schema — `from_sap_schema_15_0` added in mapper.py (PR #1531). No
+Elmhurst rebuild done for this batch — and unlike every other entry in this
+file, **lodged is NOT the comparison target here**: these are 2011 SAP-2009
+lodgements, but this calculator implements current RdSAP10, which has since
+revised several U-value tables. A gap from lodged is expected either way and
+is not, by itself, evidence of a mapper bug — nor is closeness to lodged
+evidence of correctness. What this batch actually validates: all 20
+structurally distinct real certs (different fuels, meters, secondary-heating
+types, wall constructions) map without error and produce plausible scores
+through `from_sap_schema_15_0`'s three schema-wide defaults. The 4 solid-brick
+cases below show the largest gap from lodged; `u_wall` was spot-checked
+directly against RdSAP10 Table 6 for that construction/age band and returns
+the spec-correct value, so at minimum the wall U-value lookup isn't the
+source. Real accuracy validation (engine vs Elmhurst on the SAME RdSAP10
+methodology) is still open — see comment in test_real_cert_sap_accuracy.py.
+All 20 pinned as `RealCertExpectation`s to the engine's OWN observed output.
+- [x] 🔧 100010359769 — SAP-15.0 · eng 68 (2011 lodged 68, not a target)
+- [x] 🔧 100010359788 — SAP-15.0 · eng 72 (2011 lodged 73, not a target)
+- [x] 🔧 100010086084 — SAP-15.0 · eng 53 (2011 lodged 45, not a target) · solid-brick, largest-gap group; u_wall spot-checked correct
+- [x] 🔧 100010090369 — SAP-15.0 · eng 53 (2011 lodged 47, not a target) · ditto
+- [x] 🔧 100010074470 — SAP-15.0 · eng 46 (2011 lodged 39, not a target) · ditto
+- [x] 🔧 100010100813 — SAP-15.0 · eng 59 (2011 lodged 47, not a target) · ditto
+- [x] 🔧 77179816 — SAP-15.0 · eng 76 (2011 lodged 75, not a target)
+- [x] 🔧 10070400619 — SAP-15.0 · eng 77 (2011 lodged 77, not a target)
+- [x] 🔧 77179820 — SAP-15.0 · eng 77 (2011 lodged 77, not a target)
+- [x] 🔧 10070394806 — SAP-15.0 · eng 78 (2011 lodged 77, not a target)
+- [x] 🔧 77181233 — SAP-15.0 · eng 68 (2011 lodged 69, not a target)
+- [x] 🔧 77180626 — SAP-15.0 · eng 68 (2011 lodged 68, not a target)
+- [x] 🔧 10070400618 — SAP-15.0 · eng 70 (2011 lodged 69, not a target)
+- [x] 🔧 100010350459 — SAP-15.0 · eng 65 (2011 lodged 65, not a target)
+- [x] 🔧 100010350468 — SAP-15.0 · eng 66 (2011 lodged 66, not a target)
+- [x] 🔧 100010333531 — SAP-15.0 · eng 73 (2011 lodged 74, not a target)
+- [x] 🔧 100010341489 — SAP-15.0 · eng 65 (2011 lodged 64, not a target)
+- [x] 🔧 100010341491 — SAP-15.0 · eng 62 (2011 lodged 59, not a target)
+- [x] 🔧 100010347646 — SAP-15.0 · eng 75 (2011 lodged 75, not a target)
+- [x] 🔧 100010347637 — SAP-15.0 · eng 72 (2011 lodged 72, not a target)
diff --git a/tests/domain/sap10_calculator/test_real_cert_sap_accuracy.py b/tests/domain/sap10_calculator/test_real_cert_sap_accuracy.py
index 8e5ef0ff8..b3c029dff 100644
--- a/tests/domain/sap10_calculator/test_real_cert_sap_accuracy.py
+++ b/tests/domain/sap10_calculator/test_real_cert_sap_accuracy.py
@@ -1091,24 +1091,36 @@ _EXPECTATIONS: Final[tuple[RealCertExpectation, ...]] = (
     # SAP-Schema-15.0 campaign (task a40e71c4-fd56-4a33-8677-e8643e6a5bb4,
     # portfolio 824 / scenario 1278 — the failing task that surfaced this
     # schema gap; see `from_sap_schema_15_0` in mapper.py). 20 real 2011-era
-    # LIG-15.0 lodgements sampled across the failing portfolio. 16 of 20 land
-    # exact or within 1-3 of the lodged score, confirming the mapper's three
-    # schema-wide defaults (door_count=1, WWHRS/FGHRS "none fitted",
-    # percent_draughtproofed=0) are sound.
+    # LIG-15.0 lodgements sampled across the failing portfolio.
     #
-    # The remaining 4 (086084/090369/074470/100813) share solid-brick
-    # UNINSULATED walls, age band C, and diverge from lodged by +6 to +12 —
-    # every other affected field (fuel, meter type, secondary heating type)
-    # varies independently across them, so wall construction is the only
-    # correlate. Checked `u_wall(Country.ENG, "C", 3, None,
-    # wall_insulation_type=4)` directly: it returns 1.70, RdSAP10's own
-    # published Table 6 value for solid 220-280mm brick in that age band — no
-    # mapper/U-value bug found. These are 2011 lodgements, assessed under the
-    # older SAP-2009 methodology's (higher/more conservative) solid-wall
-    # U-values; re-scoring under current RdSAP10 legitimately lands higher.
-    # Same category as the documented full-SAP-through-RdSAP and reduced-
-    # field party-wall vintage gaps elsewhere in this file — PINNED to the
-    # engine's observed value, not lodged; not tuned.
+    # NOTE on what these pins do and don't validate: `sap_score` here is the
+    # ENGINE'S OWN observed output, not an accuracy claim against the lodged
+    # `energy_rating_current`. These are 2011 certs, assessed under the SAP
+    # 2009 methodology of the day; this calculator implements the CURRENT
+    # RdSAP10 methodology, which has since revised several U-value tables
+    # (solid-wall thickness bands among them — see `u_wall` §5.7 Table 13).
+    # A 2011-vs-2026-methodology delta is therefore EXPECTED and tells you
+    # nothing about mapper correctness either way — closeness to lodged is
+    # not evidence for the mapper, and a gap from lodged is not evidence
+    # against it. Real accuracy validation needs an Elmhurst RdSAP10 rebuild
+    # (the `validate-cert-sap-accuracy` skill) on the SAME methodology as the
+    # engine, which this batch did not do.
+    #
+    # What this batch DOES validate: all 20 structurally distinct real certs
+    # (different fuels, meter types, secondary-heating types, wall
+    # constructions, portfolios) map without error through the new
+    # `from_sap_schema_15_0` path and produce plausible SAP scores — i.e. the
+    # three schema-wide defaults (door_count=1, WWHRS/FGHRS "none fitted",
+    # percent_draughtproofed=0) don't crash or produce nonsense on a diverse
+    # sample. Four of the twenty (086084/090369/074470/100813, sharing
+    # solid-brick UNINSULATED walls / age band C) show the largest gap from
+    # lodged; spot-checked `u_wall(Country.ENG, "C", 3, None,
+    # wall_insulation_type=4)` directly and it returns 1.70, matching RdSAP10's
+    # own published Table 6 for that construction/age band — so at minimum
+    # the wall U-value lookup itself is not the source of any divergence.
+    # PINNED to the engine's observed value on every case (the file's
+    # standing convention) — not tuned to lodged, and not claimed as an
+    # accuracy match either.
     RealCertExpectation(
         schema="SAP-Schema-15.0",
         sample="uprn_100010359769",