diff --git a/docs/HANDOVER_API_PROFILING.md b/docs/HANDOVER_API_PROFILING.md
index 1dcb4d42..7776af24 100644
--- a/docs/HANDOVER_API_PROFILING.md
+++ b/docs/HANDOVER_API_PROFILING.md
@@ -13,16 +13,29 @@ deproven approaches + the meter/shower data-fidelity findings), and the earlier
 `energy_rating_current`. Headline gauge:
 `PYTHONPATH=/workspaces/model python scripts/eval_api_sap_accuracy.py`.
 
-| metric | session-5 (`19235d11`) | session-6 (`a7761ea8`) | session-7 (`3e05c95e`) | **session-8 (`71b378b9`)** |
+| metric | session-6 (`a7761ea8`) | session-7 (`3e05c95e`) | session-8 (`71b378b9`) | **session-8b (`e7af6fda`)** |
 |--------|------------------|------------------|------------------|------------------|
-| **% \|err\| < 0.5** | 53.1% | 53.14% | 54.24% | **55.01%** |
-| % \|err\| < 1.0 | 68.0% | 67.99% | 69.64% | **70.08%** |
-| % \|err\| < 2.0 | ~81% | 81.85% | 83.50% | **~83.6%** |
-| mean \|err\| | 1.329 | 1.312 | 1.248 | **1.233** |
-| median \|err\| | 0.467 | 0.467 | 0.457 | **0.448** |
+| **% \|err\| < 0.5** | 53.14% | 54.24% | 55.01% | **55.12%** |
+| % \|err\| < 1.0 | 67.99% | 69.64% | 70.08% | **70.08%** |
+| % \|err\| < 2.0 | 81.85% | 83.50% | ~83.6% | **~83.6%** |
+| mean \|err\| | 1.312 | 1.248 | 1.233 | **1.232** |
+| median \|err\| | 0.467 | 0.457 | 0.448 | **0.446** |
 | computed / raises | 909 / 0 | 909 / 0 | 909 / 0 | **909 / 0** |
 | unsupported_schema | 100 (deferred) | 100 (deferred) | 100 (deferred) | 100 (deferred) |
 
+### SESSION-8b — MEV fan electricity (PCDB index plumbed), `e7af6fda`
+Follow-up to 8: the +0.9 residual on MEV after the §2 heat-loss fix was the FAN
+electricity (§5 Table 4f (230a) `SFPav × 1.22 × V`, PCDB Tables 322/329).
+`_mev_decentralised_kwh_per_yr_from_cert` already composes it but reads
+`epc.mechanical_ventilation_index_number` + `mechanical_vent_duct_type`, which the
+API builder never set → `pcdf_id is None` zeroed the fan energy on every API cert.
+Wired both through the 21.0.1 construction. The 9 MEV certs with a PCDB index
+closed +0.90 → +0.13; the **11 index-less MEV certs still sit at +1.36** — they
+need the SAP Table 4h DEFAULT specific fan power (no PCDB record), a clean next
+slice (verify the default SFP value against spec first). New e2e test + golden
+fixture (cert 1300, dMEV index 500777). NB the 21.0.0 API builder didn't get the
+8/8b ventilation edits (only 21.0.1, the corpus schema).
+
 ### SESSION-8 — API `mechanical_ventilation` enum never mapped, `71b378b9`
 Re-profiling after the sheltering fix surfaced `mechanical_ventilation=2` as a
 clean systematic over-rate (n=20, signed +1.90, 5% within 0.5, every cert