diff --git a/tradein-mvp/backend/app/services/estimator.py b/tradein-mvp/backend/app/services/estimator.py
index 34916dcd..59a86f47 100644
--- a/tradein-mvp/backend/app/services/estimator.py
+++ b/tradein-mvp/backend/app/services/estimator.py
@@ -1721,25 +1721,28 @@ def _compute_same_building_anchor(
     if floor_sigma > 0 and floor_target and total_floors_target and total_floors_target > 0:
         target_pos = floor_target / total_floors_target
 
+    # #audit-4: sigma > 0 guard — при sigma=0 Gaussian exp(-x²/0) → div/0/NaN.
+    # area_sigma=0 (отключено) → нейтральный вес 1.0; floor_sigma=0 уже гейтится выше.
+    safe_area_sigma2 = 2.0 * sigma * sigma if sigma > 0 else 0.0
+    safe_floor_sigma2 = 2.0 * floor_sigma * floor_sigma if floor_sigma > 0 else 0.0
+
     # 1. similarity weights (area × rooms × floor-position)
     weights: list[float] = []
     for c in comps:
         a = c.get("area_m2")
-        if a and area_target > 0:
-            area_w = math.exp(-((math.log(a / area_target)) ** 2) / (2.0 * sigma * sigma))
+        if a and area_target > 0 and safe_area_sigma2 > 0:
+            area_w = math.exp(-((math.log(a / area_target)) ** 2) / safe_area_sigma2)
         else:
-            area_w = 1.0  # площадь неизвестна → нейтральный area-вес
+            area_w = 1.0  # площадь неизвестна или sigma=0 → нейтральный area-вес
         rooms_match = rooms_target is not None and c.get("rooms") == rooms_target
         rooms_w = rooms_boost if rooms_match else 1.0
         floor_w = 1.0
-        if target_pos is not None:
+        if target_pos is not None and safe_floor_sigma2 > 0:
             cf = c.get("floor")
             ctf = c.get("total_floors")
             if cf and ctf and ctf > 0:
                 comp_pos = cf / ctf
-                floor_w = math.exp(
-                    -((comp_pos - target_pos) ** 2) / (2.0 * floor_sigma * floor_sigma)
-                )
+                floor_w = math.exp(-((comp_pos - target_pos) ** 2) / safe_floor_sigma2)
             # компл без floor/total_floors → нейтральный floor-вес 1.0
         weights.append(area_w * rooms_w * floor_w)
     wsum = sum(weights)
@@ -1748,6 +1751,39 @@ def _compute_same_building_anchor(
     else:
         anchor = _percentile(sorted(ppm2), 0.5)
 
+    # #audit-4: MAD-clip ПОСЛЕ similarity-weighting (за флагом estimate_sb_clip_after_weight).
+    # Видовые/топ-юниты с высоким ppm² могут быть выкинуты сырым clip'ом ДО weighting —
+    # они легитимны. После weighting (anchor = weighted mean) ищем выбросы
+    # относительно self-consistent взвешенного пространства.
+    # Используем те же effective_mad_k; если после clip < min_comps → anchor=None.
+    if settings.estimate_sb_clip_after_weight and n >= 2:
+        post_clip_idx = _mad_clip(ppm2, effective_mad_k)
+        if len(post_clip_idx) < min_comps:
+            logger.info(
+                "anchor post-weight MAD-clip #audit-4: %d comps → %d survived"
+                " (< min_comps=%d) → fallback",
+                n,
+                len(post_clip_idx),
+                min_comps,
+            )
+            return None
+        if len(post_clip_idx) < n:
+            logger.info(
+                "anchor post-weight MAD-clip #audit-4: %d comps → %d after k=%.1f×MAD",
+                n,
+                len(post_clip_idx),
+                effective_mad_k,
+            )
+            comps = [comps[i] for i in post_clip_idx]
+            ppm2 = [ppm2[i] for i in post_clip_idx]
+            weights = [weights[i] for i in post_clip_idx]
+            n = len(ppm2)
+            wsum = sum(weights)
+            if wsum > 0:
+                anchor = sum(w * p for w, p in zip(weights, ppm2, strict=True)) / wsum
+            else:
+                anchor = _percentile(sorted(ppm2), 0.5)
+
     # 2. premium uplift — топ-юнит дома (площадь ≥ p66 И комнаты ≥ медианы) И Tier A
     #    → weighted p70. Условие по комнатам отсекает мелкие юниты во флагман-домах.
     used_uplift = False