diff --git a/backend/documents_parser/tests/test_heating_systems_corpus.py b/backend/documents_parser/tests/test_heating_systems_corpus.py
index 14ccc2d9..a09e3ae7 100644
--- a/backend/documents_parser/tests/test_heating_systems_corpus.py
+++ b/backend/documents_parser/tests/test_heating_systems_corpus.py
@@ -68,13 +68,18 @@ _CORPUS_ROOT = (
 
 
 # Per-pin absolute tolerances. Worksheet `SAP value` lodges 4 d.p.,
-# (255) total fuel cost 4 d.p., (272) total CO2 4 d.p., (286) Total
-# Primary energy kWh/year 4 d.p. — pin at 1e-4 relative to lodged
-# precision so any drift outside cascade float noise fires.
-_SAP_RESID_ABS_TOLERANCE = 0.001
-_COST_RESID_ABS_TOLERANCE_GBP = 0.01
-_CO2_RESID_ABS_TOLERANCE_KG = 0.1
-_PE_RESID_ABS_TOLERANCE_KWH = 0.1
+# (255)/(355) total fuel cost 4 d.p., (272)/(383) total CO2 4 d.p.,
+# (286)/(483) Total Primary energy kWh/year 4 d.p. — so the hard floor
+# on any residual is ~5e-5 (half a unit in the last printed digit),
+# independent of cascade precision. Pin at 1e-4 on EVERY metric (per
+# [[feedback-zero-error-strict]] / [[feedback-continuous-sap-tolerance]]
+# — basically zero error across continuous SAP, cost, CO2 and PE) so
+# any drift beyond PDF print-rounding fires loudly. All 41 variants hold
+# at this tolerance; closures re-pin the smaller residual, never widen.
+_SAP_RESID_ABS_TOLERANCE = 0.0001
+_COST_RESID_ABS_TOLERANCE_GBP = 0.0001
+_CO2_RESID_ABS_TOLERANCE_KG = 0.0001
+_PE_RESID_ABS_TOLERANCE_KWH = 0.0001
 
 
 @dataclass(frozen=True)