diff --git a/apps/worker/video_processing/dedup.py b/apps/worker/video_processing/dedup.py
index 9b9afc8eb..2b96babb6 100755
--- a/apps/worker/video_processing/dedup.py
+++ b/apps/worker/video_processing/dedup.py
@@ -809,9 +809,12 @@ class VideoDeduplicator:
         """
         video_repo = SQLAlchemyGeneratedVideoRepository(session)
         if scope == "user" and user_id:
-            dur_min = duration_sec * 0.85 if duration_sec > 0 else 0
-            dur_max = duration_sec * 1.15 if duration_sec > 0 else 0
-            existing_videos = video_repo.list_by_user(user_id, duration_min=dur_min, duration_max=dur_max)
+            # Issue #1702: 不做 ±15% 时长预过滤。旧逻辑按 duration_sec 缩小候选窗口，
+            # 但局部片段复用的两个视频时长必然不同（证据视频 20s vs 11s，差 42%），
+            # ±15% 窗口让同源视频互相不可见 → is_duplicate 恒 False。
+            # 全量遍历同用户视频（与 compute_duplicate_rate 口径一致），异源视频由
+            # fusion/temporal_coverage 阈值天然过滤（校准：异源最小汉明距离 24）。
+            existing_videos = video_repo.list_by_user(user_id)
         else:
             existing_videos = video_repo.list_by_project(project_id)
 
diff --git a/tests/unit/test_dedup_1702_zero_rate_fix.py b/tests/unit/test_dedup_1702_zero_rate_fix.py
index 6482fd894..5c914bb7c 100644
--- a/tests/unit/test_dedup_1702_zero_rate_fix.py
+++ b/tests/unit/test_dedup_1702_zero_rate_fix.py
@@ -269,10 +269,13 @@ class TestSingleChunkNoRegression:
 
 
 class TestDurationPrefilterUnit:
-    def test_duration_sec_not_divided_by_1000(self):
-        """fingerprint.duration 单位是秒，传给 check_duplicate 不应再 /1000。
+    def test_user_scope_skips_duration_prefilter(self):
+        """Issue #1702: scope=user 跨项目查重不做 ±15% 时长预过滤。
 
-        旧 bug：duration/1000 → duration_max≈0.0135s，所有真实视频被过滤。
+        旧逻辑 duration/1000 单位 bug 先修成秒，但 ±15% 窗口与局部片段复用
+        根本矛盾——复用片段的两个视频时长必然不同（证据视频 20s vs 11s 差 42%），
+        窗口内找不到对方导致 is_duplicate 恒 False。最终口径：scope=user 全量
+        遍历同用户视频（与 compute_duplicate_rate 一致），不传 duration_min/max。
         """
 
         ddp = VideoDeduplicator()
@@ -283,10 +286,11 @@ class TestDurationPrefilterUnit:
             repo = MockRepo.return_value
             repo.list_by_user.return_value = []
             ddp.check_duplicate(fp, "proj1", session_magic, scope="user", user_id="u1", duration_sec=fp.duration)
-            _, kwargs = repo.list_by_user.call_args
-            # ±15% 窗口：13.5s -> [11.475, 15.525]
-            assert 11.0 < kwargs["duration_min"] < 12.0
-            assert 15.0 < kwargs["duration_max"] < 16.0
+            args, kwargs = repo.list_by_user.call_args
+            # 全量查询：不带任何时长过滤参数（局部复用必须跨时长比较）
+            assert "duration_min" not in kwargs
+            assert "duration_max" not in kwargs
+            assert args == ("u1",) or args == ()
 
 
 # ── P1-7: 颜色直方图归一化 ────────────────────────────────────
diff --git a/tests/unit/test_duplicate_rate_scope.py b/tests/unit/test_duplicate_rate_scope.py
index 4cf6f02ce..6fd9a0d08 100644
--- a/tests/unit/test_duplicate_rate_scope.py
+++ b/tests/unit/test_duplicate_rate_scope.py
@@ -132,9 +132,14 @@ class TestCheckDuplicateScopeUser:
 
 
 class TestDurationPrefilter:
-    """test_duration_prefilter：时长 ±15% 过滤."""
+    """Issue #1702: scope=user 跨项目查重不做时长预过滤。
 
-    def test_duration_prefilter_passes_correct_range(self):
+    局部片段复用的两个视频时长必然不同（证据视频 20s vs 11s，差 42%），
+    旧的 ±15% 窗口会让同源视频互相不可见 → is_duplicate 恒 False。
+    全量遍历同用户视频，异源视频由 fusion/temporal_coverage 阈值天然过滤。
+    """
+
+    def test_user_scope_no_duration_filter(self):
         from video_processing.dedup import VideoDeduplicator
 
         deduplicator = VideoDeduplicator()
@@ -153,12 +158,13 @@ class TestDurationPrefilter:
                 duration_sec=30.0,
             )
 
-        # Should pass duration_min=25.5, duration_max=34.5 (30 ± 15%)
+        # scope=user 全量遍历：位置参数只传 user_id，kwargs 不含时长过滤
         call_args = mock_repo.list_by_user.call_args
-        assert call_args[1]["duration_min"] == pytest.approx(25.5, abs=0.1)
-        assert call_args[1]["duration_max"] == pytest.approx(34.5, abs=0.1)
+        assert call_args[0] == ("user1",)
+        assert "duration_min" not in call_args[1]
+        assert "duration_max" not in call_args[1]
 
-    def test_no_duration_prefilter_when_zero(self):
+    def test_user_scope_no_duration_filter_when_zero(self):
         from video_processing.dedup import VideoDeduplicator
 
         deduplicator = VideoDeduplicator()
@@ -178,8 +184,34 @@ class TestDurationPrefilter:
             )
 
         call_args = mock_repo.list_by_user.call_args
-        assert call_args[1]["duration_min"] == 0
-        assert call_args[1]["duration_max"] == 0
+        assert "duration_min" not in call_args[1]
+        assert "duration_max" not in call_args[1]
+
+    def test_project_scope_also_no_duration_filter(self):
+        """scope=project 走 list_by_project，本来就不做时长过滤。"""
+        from video_processing.dedup import VideoDeduplicator
+
+        deduplicator = VideoDeduplicator()
+        fingerprint = _make_fingerprint(duration_ms=30000)
+        session = MagicMock()
+
+        with patch("video_processing.dedup.SQLAlchemyGeneratedVideoRepository") as MockRepo:
+            mock_repo = MockRepo.return_value
+            mock_repo.list_by_project.return_value = []
+            deduplicator.check_duplicate(
+                fingerprint,
+                "proj1",
+                session,
+                scope="project",
+                user_id="user1",
+                duration_sec=30.0,
+            )
+
+        mock_repo.list_by_project.assert_called_once()
+        call_args = mock_repo.list_by_project.call_args
+        assert call_args[0] == ("proj1",)
+        assert "duration_min" not in call_args[1]
+        assert "duration_max" not in call_args[1]
 
 
 class TestComputeDuplicateRateFormula: