diff --git a/common_util/common_util_drainage_detail.py b/common_util/common_util_drainage_detail.py
index 0f3961ea0..ac93ca754 100644
--- a/common_util/common_util_drainage_detail.py
+++ b/common_util/common_util_drainage_detail.py
@@ -26,7 +26,7 @@ from __future__ import annotations
 
 import json
 import logging
-from dataclasses import dataclass, field
+from dataclasses import dataclass, field, replace
 from pathlib import Path
 from typing import Any
 
@@ -66,6 +66,10 @@ _SCORE_WEIGHT_STRENGTH = 0.7
 _SCORE_WEIGHT_SAG = 0.3
 # 성토부(내리막)는 물이 노선 밖으로 빠지므로 관 위치로 덜 선호한다.
 _SCORE_FILL_PENALTY = 0.5
+# [자동 제안] 전체 자동(369) — 새 자리에서 이만큼(m) 안의 지금 관 = 같은 관(그 자리 그대로 ·
+# 속성 이어받음). 화면 `SAME_PIPE_M`(제안 · 같은 유역)과 같은 값 — 노선 따라감으로 cm 어긋난
+# 세월교도 같은 관.
+SAME_PIPE_M = 0.5
 
 
 @dataclass
@@ -201,6 +205,19 @@ def build_detail(
         # 자동 관 자리 = 정수 m · 일반 측점 1 m 안이면 그 측점(234-1) — 확정본(위)은 단추로만
         placed = place_pipes(vertices, base, routing.strength_curve, fill=auto is not None)
         pipes = snap_candidates(placed, vertices)
+        if confirmed_chainages:
+            kept = pipes_from_chainages(vertices, confirmed_chainages)
+            pipes = [
+                replace(
+                    min(
+                        (k for k in kept if abs(k.chainage_m - pipe.chainage_m) <= SAME_PIPE_M),
+                        key=lambda k: abs(k.chainage_m - pipe.chainage_m),
+                        default=pipe,
+                    ),
+                    reason=pipe.reason,
+                )
+                for pipe in pipes
+            ]
     candidates = suggest_pipe_positions(vertices, pipes, routing.strength_curve)
 
     detail = DrainageDetail(
diff --git a/resources/tester/test_369_drainage_auto.py b/resources/tester/test_369_drainage_auto.py
index 2022901a8..e342a71ea 100644
--- a/resources/tester/test_369_drainage_auto.py
+++ b/resources/tester/test_369_drainage_auto.py
@@ -56,7 +56,7 @@ def test_all_은_세류선_더하기_100m_보충_지금_목록_무시(tmp_path):
     reasons = [p.reason for p in detail.pipes]
     places = [p.chainage_m for p in detail.pipes]
     assert reasons.count("stream") == 1 and reasons.count("spacing") == 2
-    assert 150.0 in places and 10.0 not in places
+    assert 150.02 in places and 10.0 not in places  # 세류선 150 m 0.5 m 안의 지금 관 = 그 자리
     gaps = np.diff([0.0, *places, 300.0])
     assert gaps.max() <= 100.0 and not detail.pipe_candidates
 
@@ -78,7 +78,7 @@ def _build(tmp_path, monkeypatch, points, auto):
 
 def test_all_같은_자리_관은_속성_id_유지_새_관은_기본값(tmp_path, monkeypatch):
     kept = PipePoint(
-        chainage_m=150.03,
+        chainage_m=150.3,  # 세류선 150 m 에서 0.3 m — 노선 따라감으로 어긋난 같은 관
         source="user",
         facility="ford_bridge",
         options={"ford_width_m": 4.0},
@@ -88,6 +88,7 @@ def test_all_같은_자리_관은_속성_id_유지_새_관은_기본값(tmp_path
     _, carried = _build(tmp_path, monkeypatch, [gone, kept], "all")
     ford = [p for p in carried if p.id == "keep"]
     assert len(ford) == 1 and ford[0].facility == "ford_bridge" and ford[0].source == "user"
+    assert ford[0].chainage_m == 150.3  # 그 자리 그대로
     assert all(p.id != "gone" for p in carried)
     fresh = [p for p in carried if p.id != "keep"]
     assert len(fresh) == 2 and all(p.source == "spacing" for p in fresh)