diff --git a/tests/unit/domain/test_video_concat.py b/tests/unit/domain/test_video_concat.py
new file mode 100755
index 000000000..86bfff73d
--- /dev/null
+++ b/tests/unit/domain/test_video_concat.py
@@ -0,0 +1,392 @@
+"""video_concat 视频拼接配置单测."""
+
+import pytest
+from domain.video_concat import (
+    ALLOWED_VIDEO_EXTENSIONS,
+    CONCAT_DEMUXER_REQUIRED_PARAMS,
+    MAX_CONCAT_SEGMENTS,
+    ConcatConfig,
+    ConcatSegment,
+)
+
+# ── 常量测试 ─────────────────────────────────────────────────────────────────
+
+
+class TestConstants:
+    """模块常量"""
+
+    def test_max_concat_segments(self):
+        assert MAX_CONCAT_SEGMENTS == 50
+
+    def test_allowed_extensions(self):
+        assert ".mp4" in ALLOWED_VIDEO_EXTENSIONS
+        assert ".mov" in ALLOWED_VIDEO_EXTENSIONS
+        assert ".avi" in ALLOWED_VIDEO_EXTENSIONS
+        assert ".mkv" in ALLOWED_VIDEO_EXTENSIONS
+        assert ".webm" in ALLOWED_VIDEO_EXTENSIONS
+        assert ".flv" in ALLOWED_VIDEO_EXTENSIONS
+        assert ".wmv" in ALLOWED_VIDEO_EXTENSIONS
+
+    def test_concat_demuxer_params(self):
+        params = CONCAT_DEMUXER_REQUIRED_PARAMS
+        assert "codec_name" in params
+        assert "width" in params
+        assert "height" in params
+        assert "r_frame_rate" in params
+        assert "pix_fmt" in params
+        assert "sample_rate" in params
+        assert "channels" in params
+        assert "audio_codec" in params
+        assert len(params) == 8
+
+
+# ── ConcatSegment ────────────────────────────────────────────────────────────
+
+
+class TestConcatSegmentDefaults:
+    """ConcatSegment 默认值"""
+
+    def test_required_path(self):
+        s = ConcatSegment(video_path="/video.mp4")
+        assert s.video_path == "/video.mp4"
+        assert s.start_time == 0.0
+        assert s.duration == 0.0
+        assert s.has_audio is True
+
+    def test_all_custom(self):
+        s = ConcatSegment(
+            video_path="/clip.mp4",
+            start_time=5.0,
+            duration=10.0,
+            has_audio=False,
+        )
+        assert s.video_path == "/clip.mp4"
+        assert s.start_time == 5.0
+        assert s.duration == 10.0
+        assert s.has_audio is False
+
+
+class TestConcatSegmentFromDict:
+    """ConcatSegment.from_dict"""
+
+    def test_none_returns_empty_path(self):
+        s = ConcatSegment.from_dict(None)
+        assert s.video_path == ""
+        assert s.is_valid is False
+
+    def test_empty_dict(self):
+        s = ConcatSegment.from_dict({})
+        assert s.video_path == ""
+
+    def test_not_dict(self):
+        s = ConcatSegment.from_dict("not a dict")
+        assert s.video_path == ""
+
+    def test_full_dict(self):
+        s = ConcatSegment.from_dict(
+            {
+                "video_path": "/clip.mp4",
+                "start_time": 2.5,
+                "duration": 15.0,
+                "has_audio": False,
+            }
+        )
+        assert s.video_path == "/clip.mp4"
+        assert s.start_time == 2.5
+        assert s.duration == 15.0
+        assert s.has_audio is False
+
+    def test_invalid_start_time_falls_back(self):
+        s = ConcatSegment.from_dict({"video_path": "/a.mp4", "start_time": "bad"})
+        assert s.start_time == 0.0
+
+    def test_negative_start_time_clamped(self):
+        s = ConcatSegment.from_dict({"video_path": "/a.mp4", "start_time": -5.0})
+        assert s.start_time == 0.0
+
+    def test_invalid_duration_falls_back(self):
+        s = ConcatSegment.from_dict({"video_path": "/a.mp4", "duration": None})
+        assert s.duration == 0.0
+
+    def test_negative_duration_clamped(self):
+        s = ConcatSegment.from_dict({"video_path": "/a.mp4", "duration": -10.0})
+        assert s.duration == 0.0
+
+    def test_has_audio_default_true(self):
+        s = ConcatSegment.from_dict({"video_path": "/a.mp4"})
+        assert s.has_audio is True
+
+    def test_has_audio_false(self):
+        s = ConcatSegment.from_dict({"video_path": "/a.mp4", "has_audio": False})
+        assert s.has_audio is False
+
+    def test_path_is_string(self):
+        s = ConcatSegment.from_dict({"video_path": 123})
+        assert s.video_path == "123"
+
+
+class TestConcatSegmentProperties:
+    """ConcatSegment 属性方法"""
+
+    def test_is_valid_true(self):
+        s = ConcatSegment(video_path="/a.mp4")
+        assert s.is_valid is True
+
+    def test_is_valid_false_empty(self):
+        s = ConcatSegment(video_path="")
+        assert s.is_valid is False
+
+    def test_effective_duration_positive(self):
+        s = ConcatSegment(video_path="/a.mp4", duration=10.0)
+        assert s.effective_duration == 10.0
+
+    def test_effective_duration_zero(self):
+        s = ConcatSegment(video_path="/a.mp4", duration=0.0)
+        assert s.effective_duration == 0.0
+
+    def test_effective_duration_negative(self):
+        s = ConcatSegment(video_path="/a.mp4", duration=-5.0)
+        assert s.effective_duration == 0.0
+
+
+# ── ConcatConfig ─────────────────────────────────────────────────────────────
+
+
+class TestConcatConfigDefaults:
+    """ConcatConfig 默认值"""
+
+    def test_default_values(self):
+        c = ConcatConfig()
+        assert c.segments == []
+        assert c.output_width == 0
+        assert c.output_height == 0
+        assert c.output_fps == 0.0
+        assert c.force_reencode is False
+        assert c.transition == "none"
+        assert c.transition_duration == 0.3
+
+
+class TestConcatConfigFromDict:
+    """ConcatConfig.from_config_dict"""
+
+    def test_none_returns_default(self):
+        c = ConcatConfig.from_config_dict(None)
+        assert c.segments == []
+
+    def test_empty_dict_returns_default(self):
+        c = ConcatConfig.from_config_dict({})
+        assert c.segments == []
+
+    def test_not_dict_returns_default(self):
+        c = ConcatConfig.from_config_dict("config")
+        assert c.segments == []
+
+    def test_single_segment(self):
+        c = ConcatConfig.from_config_dict(
+            {
+                "segments": [
+                    {"video_path": "/a.mp4", "duration": 10.0},
+                ],
+            }
+        )
+        assert len(c.segments) == 1
+        assert c.segments[0].video_path == "/a.mp4"
+
+    def test_multiple_segments(self):
+        c = ConcatConfig.from_config_dict(
+            {
+                "segments": [
+                    {"video_path": "/a.mp4", "duration": 10.0},
+                    {"video_path": "/b.mp4", "duration": 20.0},
+                    {"video_path": "/c.mp4", "duration": 15.0},
+                ],
+            }
+        )
+        assert len(c.segments) == 3
+
+    def test_skip_no_path_segments(self):
+        c = ConcatConfig.from_config_dict(
+            {
+                "segments": [
+                    {"video_path": "/a.mp4"},
+                    {"video_path": ""},
+                    {"duration": 5.0},  # 没有 video_path
+                    {"video_path": "/b.mp4"},
+                ],
+            }
+        )
+        assert len(c.segments) == 2
+
+    def test_skip_non_dict_segments(self):
+        c = ConcatConfig.from_config_dict(
+            {
+                "segments": [
+                    {"video_path": "/a.mp4"},
+                    "not a dict",
+                    123,
+                    None,
+                    {"video_path": "/b.mp4"},
+                ],
+            }
+        )
+        assert len(c.segments) == 2
+
+    def test_output_resolution(self):
+        c = ConcatConfig.from_config_dict(
+            {
+                "segments": [{"video_path": "/a.mp4"}],
+                "output_width": 1920,
+                "output_height": 1080,
+            }
+        )
+        assert c.output_width == 1920
+        assert c.output_height == 1080
+
+    def test_output_width_clamped(self):
+        c = ConcatConfig.from_config_dict({"output_width": -100})
+        assert c.output_width == 0
+
+    def test_invalid_output_width_falls_back(self):
+        c = ConcatConfig.from_config_dict({"output_width": "wide"})
+        assert c.output_width == 0
+
+    def test_output_fps(self):
+        c = ConcatConfig.from_config_dict({"output_fps": 30.0})
+        assert c.output_fps == 30.0
+
+    def test_output_fps_clamped(self):
+        c = ConcatConfig.from_config_dict({"output_fps": -1.0})
+        assert c.output_fps == 0.0
+
+    def test_invalid_output_fps_falls_back(self):
+        c = ConcatConfig.from_config_dict({"output_fps": "fast"})
+        assert c.output_fps == 0.0
+
+    def test_force_reencode_true(self):
+        c = ConcatConfig.from_config_dict({"force_reencode": True})
+        assert c.force_reencode is True
+
+    def test_transition_crossfade(self):
+        c = ConcatConfig.from_config_dict({"transition": "crossfade"})
+        assert c.transition == "crossfade"
+
+    def test_transition_duration(self):
+        c = ConcatConfig.from_config_dict({"transition_duration": 1.0})
+        assert c.transition_duration == 1.0
+
+    def test_transition_duration_min_clamped(self):
+        c = ConcatConfig.from_config_dict({"transition_duration": 0.01})
+        # max(0.1, 0.01) = 0.1
+        assert c.transition_duration == 0.1
+        # 代码里 transition_duration = max(0.1, ...)，默认 0.3
+        # 0.01 < 0.1 ，所以被钳制到 0.1
+
+    def test_invalid_transition_duration_falls_back(self):
+        c = ConcatConfig.from_config_dict({"transition_duration": "long"})
+        assert c.transition_duration == 0.3
+
+    def test_segments_not_list_ignored(self):
+        c = ConcatConfig.from_config_dict({"segments": "not a list"})
+        assert c.segments == []
+
+
+class TestConcatConfigProperties:
+    """ConcatConfig 属性方法"""
+
+    def _make_config(self, n=3):
+        return ConcatConfig.from_config_dict(
+            {
+                "segments": [{"video_path": f"/s{i}.mp4", "duration": 10.0 + i} for i in range(n)],
+            }
+        )
+
+    def test_has_effect_true(self):
+        c = self._make_config(3)
+        assert c.has_effect is True
+
+    def test_has_effect_false_one_segment(self):
+        c = self._make_config(1)
+        assert c.has_effect is False
+
+    def test_has_effect_false_empty(self):
+        c = ConcatConfig()
+        assert c.has_effect is False
+
+    def test_valid_segment_count(self):
+        c = self._make_config(5)
+        assert c.valid_segment_count == 5
+
+    def test_total_segments_alias(self):
+        c = self._make_config(4)
+        assert c.total_segments == 4
+        assert c.total_segments == c.valid_segment_count
+
+    def test_first_valid_segment(self):
+        c = self._make_config(3)
+        first = c.first_valid_segment
+        assert first is not None
+        assert first.video_path == "/s0.mp4"
+
+    def test_first_valid_segment_empty(self):
+        c = ConcatConfig()
+        assert c.first_valid_segment is None
+
+    def test_estimated_total_duration(self):
+        c = ConcatConfig(
+            segments=[
+                ConcatSegment("/a.mp4", duration=10.0),
+                ConcatSegment("/b.mp4", duration=20.0),
+                ConcatSegment("/c.mp4", duration=0.0),  # 不计入
+            ]
+        )
+        assert c.estimated_total_duration == 30.0
+
+    def test_estimated_total_duration_empty(self):
+        c = ConcatConfig()
+        assert c.estimated_total_duration == 0.0
+
+    def test_clamp_segments_within_limit(self):
+        c = self._make_config(10)
+        original = len(c.segments)
+        c.clamp_segments(max_segments=50)
+        assert len(c.segments) == original
+
+    def test_clamp_segments_over_limit(self):
+        c = self._make_config(10)
+        c.clamp_segments(max_segments=3)
+        assert len(c.segments) == 3
+        assert c.segments[0].video_path == "/s0.mp4"
+        assert c.segments[2].video_path == "/s2.mp4"
+
+    def test_clamp_segments_default_max(self):
+        # 默认应该是 MAX_CONCAT_SEGMENTS
+        c = ConcatConfig(segments=[ConcatSegment(f"/s{i}.mp4") for i in range(100)])
+        c.clamp_segments()
+        assert len(c.segments) == MAX_CONCAT_SEGMENTS
+
+
+class TestTransitionDurationClamp:
+    """transition_duration 钳制边界"""
+
+    def test_min_boundary_01(self):
+        c = ConcatConfig.from_config_dict({"transition_duration": 0.1})
+        assert c.transition_duration == 0.1
+
+    def test_below_min_clamped(self):
+        c = ConcatConfig.from_config_dict({"transition_duration": 0.05})
+        # max(0.1, 0.05) = 0.1
+        assert c.transition_duration == 0.1
+
+    def test_large_duration_ok(self):
+        c = ConcatConfig.from_config_dict({"transition_duration": 5.0})
+        assert c.transition_duration == 5.0
+
+    def test_zero_clamped(self):
+        c = ConcatConfig.from_config_dict({"transition_duration": 0.0})
+        # max(0.1, 0.0) = 0.1
+        assert c.transition_duration == 0.1
+
+    def test_negative_clamped(self):
+        c = ConcatConfig.from_config_dict({"transition_duration": -1.0})
+        # max(0.1, -1.0) = 0.1
+        assert c.transition_duration == 0.1