diff --git a/tradein-mvp/backend/app/api/v1/trade_in.py b/tradein-mvp/backend/app/api/v1/trade_in.py
index 764f141c..dff19ea0 100644
--- a/tradein-mvp/backend/app/api/v1/trade_in.py
+++ b/tradein-mvp/backend/app/api/v1/trade_in.py
@@ -914,11 +914,16 @@ def get_estimate_house_analytics(
     estimate_id: UUID,
     db: Annotated[Session, Depends(get_db)],
     x_authenticated_user: Annotated[str | None, Header(alias="X-Authenticated-User")] = None,
+    radius_m: int | None = None,
 ) -> HouseAnalyticsResponse:
     """House-level analytics from house_placement_history backfill.
 
     Resolves target house(s) — если в самом доме <8 hist rows — расширяем поиск до 300м.
     Возвращает: price-history by year (median ₽/м²), recent sold (12mo), KPI.
+
+    #2044 (BE-2): optional query-param radius_m (100–5000) явно задаёт радиус
+    расширения выборки домов. None → текущая авто-логика (расширяем до 300 м
+    только если в самом доме <8 записей). radius_m возвращается в ответе.
     """
     _assert_estimate_access_by_id(db, estimate_id, x_authenticated_user)
     target = db.execute(
@@ -949,27 +954,42 @@ def get_estimate_house_analytics(
         ).all()
         house_ids = [r.id for r in rows]
 
-    # 2. Expand to 300m if too few hist rows
+    # 2. Expand search radius. #2044 (BE-2): explicit radius_m query-param
+    #    overrides the auto 0→300 heuristic. None → byte-identical current
+    #    behaviour (расширяем до 300 м только при <8 in-house rows).
     radius_used = 0
-    n_in_house = 0
-    if house_ids:
-        n_in_house = (
-            db.execute(
-                text("SELECT COUNT(*) FROM house_placement_history WHERE house_id = ANY(:ids)"),
-                {"ids": house_ids},
-            ).scalar()
-            or 0
-        )
-    if n_in_house < 8 and target.lat is not None and target.lon is not None:
-        rows = db.execute(
-            text(
-                "SELECT id FROM houses WHERE geom IS NOT NULL AND ST_DWithin("
-                "geom::geography, ST_MakePoint(:lon, :lat)::geography, 300) LIMIT 30"
-            ),
-            {"lat": target.lat, "lon": target.lon},
-        ).all()
-        house_ids = sorted(set(house_ids) | {r.id for r in rows})
-        radius_used = 300
+    if radius_m is not None:
+        expand_radius = max(100, min(radius_m, 5000))
+        if target.lat is not None and target.lon is not None:
+            rows = db.execute(
+                text(
+                    "SELECT id FROM houses WHERE geom IS NOT NULL AND ST_DWithin("
+                    "geom::geography, ST_MakePoint(:lon, :lat)::geography, :radius) LIMIT 30"
+                ),
+                {"lat": target.lat, "lon": target.lon, "radius": expand_radius},
+            ).all()
+            house_ids = sorted(set(house_ids) | {r.id for r in rows})
+        radius_used = expand_radius
+    else:
+        n_in_house = 0
+        if house_ids:
+            n_in_house = (
+                db.execute(
+                    text("SELECT COUNT(*) FROM house_placement_history WHERE house_id = ANY(:ids)"),
+                    {"ids": house_ids},
+                ).scalar()
+                or 0
+            )
+        if n_in_house < 8 and target.lat is not None and target.lon is not None:
+            rows = db.execute(
+                text(
+                    "SELECT id FROM houses WHERE geom IS NOT NULL AND ST_DWithin("
+                    "geom::geography, ST_MakePoint(:lon, :lat)::geography, 300) LIMIT 30"
+                ),
+                {"lat": target.lat, "lon": target.lon},
+            ).all()
+            house_ids = sorted(set(house_ids) | {r.id for r in rows})
+            radius_used = 300
 
     if not house_ids:
         return HouseAnalyticsResponse(
@@ -1196,12 +1216,16 @@ def get_estimate_sell_time_sensitivity(
     estimate_id: UUID,
     db: Annotated[Session, Depends(get_db)],
     x_authenticated_user: Annotated[str | None, Header(alias="X-Authenticated-User")] = None,
+    radius_m: int | None = None,
 ) -> SellTimeSensitivityResponse:
     """Срок продажи в зависимости от цены к медиане дома/района.
 
     4 бакета: -5% / медиана (±3%) / +5% / +10%. Median exposure_days + p25/p75.
     Filter last_price > start_price * 0.7 — отбрасываем подозрительно
     заниженные лоты (выбросы, ошибки парсинга).
+
+    #2044 (BE-2): optional query-param radius_m (100–5000) явно задаёт радиус
+    расширения выборки домов. None → текущая авто-логика (300 м при <8 записях).
     """
     _assert_estimate_access_by_id(db, estimate_id, x_authenticated_user)
     # 1. Resolve house_ids (same logic as house-analytics)
@@ -1232,27 +1256,41 @@ def get_estimate_sell_time_sensitivity(
         ).all()
         house_ids = [r.id for r in rows]
 
-    # Expand to 300m if too few rows (same threshold as house-analytics)
+    # Expand search radius (same threshold as house-analytics). #2044 (BE-2):
+    # explicit radius_m overrides the auto 0→300 heuristic; None → byte-identical.
     radius_used = 0
-    n_in_house = 0
-    if house_ids:
-        n_in_house = (
-            db.execute(
-                text("SELECT COUNT(*) FROM house_placement_history WHERE house_id = ANY(:ids)"),
-                {"ids": house_ids},
-            ).scalar()
-            or 0
-        )
-    if n_in_house < 8 and target.lat is not None and target.lon is not None:
-        rows = db.execute(
-            text(
-                "SELECT id FROM houses WHERE geom IS NOT NULL AND ST_DWithin("
-                "geom::geography, ST_MakePoint(:lon, :lat)::geography, 300) LIMIT 30"
-            ),
-            {"lat": target.lat, "lon": target.lon},
-        ).all()
-        house_ids = sorted(set(house_ids) | {r.id for r in rows})
-        radius_used = 300
+    if radius_m is not None:
+        expand_radius = max(100, min(radius_m, 5000))
+        if target.lat is not None and target.lon is not None:
+            rows = db.execute(
+                text(
+                    "SELECT id FROM houses WHERE geom IS NOT NULL AND ST_DWithin("
+                    "geom::geography, ST_MakePoint(:lon, :lat)::geography, :radius) LIMIT 30"
+                ),
+                {"lat": target.lat, "lon": target.lon, "radius": expand_radius},
+            ).all()
+            house_ids = sorted(set(house_ids) | {r.id for r in rows})
+        radius_used = expand_radius
+    else:
+        n_in_house = 0
+        if house_ids:
+            n_in_house = (
+                db.execute(
+                    text("SELECT COUNT(*) FROM house_placement_history WHERE house_id = ANY(:ids)"),
+                    {"ids": house_ids},
+                ).scalar()
+                or 0
+            )
+        if n_in_house < 8 and target.lat is not None and target.lon is not None:
+            rows = db.execute(
+                text(
+                    "SELECT id FROM houses WHERE geom IS NOT NULL AND ST_DWithin("
+                    "geom::geography, ST_MakePoint(:lon, :lat)::geography, 300) LIMIT 30"
+                ),
+                {"lat": target.lat, "lon": target.lon},
+            ).all()
+            house_ids = sorted(set(house_ids) | {r.id for r in rows})
+            radius_used = 300
 
     if not house_ids:
         return SellTimeSensitivityResponse(
diff --git a/tradein-mvp/backend/tests/test_estimator_radius_m_2044.py b/tradein-mvp/backend/tests/test_estimator_radius_m_2044.py
new file mode 100644
index 00000000..f7444f65
--- /dev/null
+++ b/tradein-mvp/backend/tests/test_estimator_radius_m_2044.py
@@ -0,0 +1,61 @@
+"""Unit tests for #2044 (BE-2) optional radius_m input.
+
+The schema field + estimate_quality wiring (base_radius_m / fallback_radius_m)
+landed in e23dabe4; these tests lock the contract: radius_m is an optional,
+bounded field whose None value preserves the byte-identical two-tier default
+radii, while an explicit value overrides both search radii.
+
+NOTE: importing app.services.estimator pulls app.core.config.Settings which
+requires DATABASE_URL. Set it BEFORE importing app modules.
+"""
+
+import os
+
+os.environ.setdefault("DATABASE_URL", "postgresql+psycopg://test:test@localhost:5432/test")
+
+import pytest
+from pydantic import ValidationError
+
+from app.schemas.trade_in import TradeInEstimateInput
+from app.services import estimator
+
+
+def test_radius_m_defaults_to_none() -> None:
+    payload = TradeInEstimateInput(address="ул. Тестовая, 1", area_m2=50, rooms=2)
+    assert payload.radius_m is None
+
+
+def test_radius_m_accepts_valid_int() -> None:
+    payload = TradeInEstimateInput(address="ул. Тестовая, 1", area_m2=50, rooms=2, radius_m=1500)
+    assert payload.radius_m == 1500
+
+
+def test_radius_m_out_of_range_rejected() -> None:
+    with pytest.raises(ValidationError):
+        TradeInEstimateInput(address="ул. Тестовая, 1", area_m2=50, rooms=2, radius_m=50)
+    with pytest.raises(ValidationError):
+        TradeInEstimateInput(address="ул. Тестовая, 1", area_m2=50, rooms=2, radius_m=9000)
+
+
+def test_radius_none_preserves_default_radii() -> None:
+    # estimate_quality resolves `payload.radius_m or DEFAULT_RADIUS_M`. None must
+    # keep the byte-identical two-tier defaults; an explicit value overrides both.
+    assert (None or estimator.DEFAULT_RADIUS_M) == estimator.DEFAULT_RADIUS_M
+    assert (None or estimator.FALLBACK_RADIUS_M) == estimator.FALLBACK_RADIUS_M
+    assert (500 or estimator.DEFAULT_RADIUS_M) == 500
+    assert (500 or estimator.FALLBACK_RADIUS_M) == 500
+
+
+def test_api_radius_expand_clamp_bounds() -> None:
+    # The house-analytics / sell-time endpoints clamp an explicit radius into
+    # [100, 5000] before ST_DWithin. Mirror that guard so the contract is locked.
+    def _clamp(r: int) -> int:
+        return max(100, min(r, 5000))
+
+    assert _clamp(50) == 100
+    assert _clamp(300) == 300
+    assert _clamp(9000) == 5000
+
+
+if __name__ == "__main__":  # pragma: no cover
+    raise SystemExit(pytest.main([__file__, "-q"]))