diff --git a/tests/unit/domain/test_speed_config.py b/tests/unit/domain/test_speed_config.py
new file mode 100755
index 000000000..795402d9e
--- /dev/null
+++ b/tests/unit/domain/test_speed_config.py
@@ -0,0 +1,453 @@
+"""speed_config 调速配置领域模型单测."""
+
+import pytest
+from domain.speed_config import (
+    DEFAULT_SPEED,
+    MAX_SPEED,
+    MIN_SPEED,
+    SpeedConfig,
+    adjust_duration,
+    build_audio_filter,
+    build_clip_speed_filter,
+    build_video_filter,
+    resolve_clip_speed,
+)
+
+# ── 常量测试 ─────────────────────────────────────────────────────────────────
+
+
+class TestConstants:
+    """模块常量"""
+
+    def test_speed_limits(self):
+        assert MIN_SPEED == 0.25
+        assert MAX_SPEED == 4.0
+        assert DEFAULT_SPEED == 1.0
+
+
+# ── SpeedConfig 默认值与基础 ────────────────────────────────────────────────
+
+
+class TestSpeedConfigDefaults:
+    """SpeedConfig 默认值"""
+
+    def test_default_values(self):
+        c = SpeedConfig()
+        assert c.speed == 1.0
+        assert c.pitch_correct is True
+
+    def test_custom_values(self):
+        c = SpeedConfig(speed=2.0, pitch_correct=False)
+        assert c.speed == 2.0
+        assert c.pitch_correct is False
+
+
+# ── SpeedConfig.parse ───────────────────────────────────────────────────────
+
+
+class TestSpeedConfigParse:
+    """SpeedConfig.parse 工厂方法"""
+
+    def test_none_returns_default(self):
+        c = SpeedConfig.parse(None)
+        assert c.speed == 1.0
+        assert c.pitch_correct is True
+
+    def test_empty_dict_returns_default(self):
+        c = SpeedConfig.parse({})
+        assert c.speed == 1.0
+
+    def test_not_dict_returns_default(self):
+        c = SpeedConfig.parse("not a dict")
+        assert c.speed == 1.0
+
+    def test_valid_speed(self):
+        c = SpeedConfig.parse({"speed": 2.0})
+        assert c.speed == 2.0
+
+    def test_valid_speed_int(self):
+        c = SpeedConfig.parse({"speed": 2})
+        assert c.speed == 2.0
+        assert isinstance(c.speed, float)
+
+    def test_pitch_correct_false(self):
+        c = SpeedConfig.parse({"pitch_correct": False})
+        assert c.pitch_correct is False
+
+    def test_pitch_correct_non_bool_falls_back(self):
+        c = SpeedConfig.parse({"pitch_correct": "true"})
+        assert c.pitch_correct is True
+
+    def test_invalid_speed_string_falls_back(self):
+        c = SpeedConfig.parse({"speed": "fast"})
+        assert c.speed == 1.0
+
+    def test_speed_below_min_clamped(self):
+        c = SpeedConfig.parse({"speed": 0.1})
+        assert c.speed == MIN_SPEED
+
+    def test_speed_above_max_clamped(self):
+        c = SpeedConfig.parse({"speed": 10.0})
+        assert c.speed == MAX_SPEED
+
+    def test_zero_speed_falls_back_to_default(self):
+        c = SpeedConfig.parse({"speed": 0})
+        assert c.speed == DEFAULT_SPEED
+
+    def test_negative_speed_falls_back(self):
+        c = SpeedConfig.parse({"speed": -1.0})
+        assert c.speed == DEFAULT_SPEED
+
+    def test_min_speed_boundary(self):
+        c = SpeedConfig.parse({"speed": 0.25})
+        assert c.speed == 0.25
+
+    def test_max_speed_boundary(self):
+        c = SpeedConfig.parse({"speed": 4.0})
+        assert c.speed == 4.0
+
+
+# ── SpeedConfig.clamp ───────────────────────────────────────────────────────
+
+
+class TestSpeedConfigClamp:
+    """SpeedConfig.clamp 方法"""
+
+    def test_normal_speed_no_change(self):
+        c = SpeedConfig(speed=1.5)
+        c.clamp()
+        assert c.speed == 1.5
+
+    def test_zero_speed_reset_default(self):
+        c = SpeedConfig(speed=0.0)
+        c.clamp()
+        assert c.speed == DEFAULT_SPEED
+
+    def test_negative_speed_reset_default(self):
+        c = SpeedConfig(speed=-0.5)
+        c.clamp()
+        assert c.speed == DEFAULT_SPEED
+
+    def test_below_min_clamped(self):
+        c = SpeedConfig(speed=0.1)
+        c.clamp()
+        assert c.speed == MIN_SPEED
+
+    def test_above_max_clamped(self):
+        c = SpeedConfig(speed=5.0)
+        c.clamp()
+        assert c.speed == MAX_SPEED
+
+    def test_exact_min_unchanged(self):
+        c = SpeedConfig(speed=MIN_SPEED)
+        c.clamp()
+        assert c.speed == MIN_SPEED
+
+    def test_exact_max_unchanged(self):
+        c = SpeedConfig(speed=MAX_SPEED)
+        c.clamp()
+        assert c.speed == MAX_SPEED
+
+
+# ── SpeedConfig 属性方法 ────────────────────────────────────────────────────
+
+
+class TestSpeedConfigProperties:
+    """SpeedConfig 属性方法"""
+
+    def test_is_original_true(self):
+        c = SpeedConfig(speed=1.0)
+        assert c.is_original is True
+
+    def test_is_original_very_close(self):
+        c = SpeedConfig(speed=1.0 + 1e-7)
+        assert c.is_original is True
+
+    def test_is_original_false_fast(self):
+        c = SpeedConfig(speed=1.5)
+        assert c.is_original is False
+
+    def test_is_original_false_slow(self):
+        c = SpeedConfig(speed=0.8)
+        assert c.is_original is False
+
+    def test_is_fast_true(self):
+        c = SpeedConfig(speed=2.0)
+        assert c.is_fast is True
+
+    def test_is_fast_false(self):
+        c = SpeedConfig(speed=0.5)
+        assert c.is_fast is False
+
+    def test_is_fast_at_one(self):
+        c = SpeedConfig(speed=1.0)
+        assert c.is_fast is False
+
+    def test_is_slow_true(self):
+        c = SpeedConfig(speed=0.5)
+        assert c.is_slow is True
+
+    def test_is_slow_false(self):
+        c = SpeedConfig(speed=2.0)
+        assert c.is_slow is False
+
+    def test_is_slow_at_one(self):
+        c = SpeedConfig(speed=1.0)
+        assert c.is_slow is False
+
+
+# ── build_video_filter ───────────────────────────────────────────────────────
+
+
+class TestBuildVideoFilter:
+    """build_video_filter 视频滤镜构建"""
+
+    def test_original_speed_empty(self):
+        c = SpeedConfig(speed=1.0)
+        assert build_video_filter(c) == ""
+
+    def test_double_speed(self):
+        c = SpeedConfig(speed=2.0)
+        result = build_video_filter(c)
+        assert "setpts=PTS/2.0" in result
+
+    def test_half_speed(self):
+        c = SpeedConfig(speed=0.5)
+        result = build_video_filter(c)
+        assert "setpts=PTS/0.5" in result
+
+    def test_format_precision(self):
+        c = SpeedConfig(speed=1.5)
+        result = build_video_filter(c)
+        # 应该是 4 位小数
+        assert "1.5000" in result
+
+    def test_min_speed(self):
+        c = SpeedConfig(speed=0.25)
+        result = build_video_filter(c)
+        assert result.startswith("setpts=PTS/")
+
+    def test_max_speed(self):
+        c = SpeedConfig(speed=4.0)
+        result = build_video_filter(c)
+        assert "4.0000" in result
+
+
+# ── build_audio_filter / atempo 拆分 ────────────────────────────────────────
+
+
+class TestBuildAudioFilter:
+    """build_audio_filter 音频滤镜构建"""
+
+    def test_original_speed_empty(self):
+        c = SpeedConfig(speed=1.0)
+        assert build_audio_filter(c) == ""
+
+    def test_within_range_single_stage(self):
+        c = SpeedConfig(speed=1.5)
+        result = build_audio_filter(c)
+        assert result == "atempo=1.5000"
+
+    def test_05_speed_single_stage(self):
+        c = SpeedConfig(speed=0.5)
+        result = build_audio_filter(c)
+        assert result == "atempo=0.5000"
+
+    def test_20_speed_single_stage(self):
+        c = SpeedConfig(speed=2.0)
+        result = build_audio_filter(c)
+        assert result == "atempo=2.0000"
+
+    def test_4x_speed_two_stages(self):
+        c = SpeedConfig(speed=4.0)
+        result = build_audio_filter(c)
+        # 2.0 * 2.0 = 4.0
+        assert result == "atempo=2.0000,atempo=2.0000"
+
+    def test_025_speed_two_stages(self):
+        c = SpeedConfig(speed=0.25)
+        result = build_audio_filter(c)
+        # 0.5 * 0.5 = 0.25
+        assert result == "atempo=0.5000,atempo=0.5000"
+
+    def test_3x_speed_two_stages(self):
+        c = SpeedConfig(speed=3.0)
+        result = build_audio_filter(c)
+        # 2.0 * 1.5 = 3.0
+        stages = result.split(",")
+        assert len(stages) == 2
+        assert "atempo=2.0000" in stages[0]
+        assert "atempo=1.5000" in stages[1]
+
+    def test_03_speed_two_stages(self):
+        c = SpeedConfig(speed=0.3)
+        result = build_audio_filter(c)
+        stages = result.split(",")
+        assert len(stages) == 2
+        # 0.5 * 0.6 = 0.3
+        assert "atempo=0.5000" in stages[0]
+
+    def test_format_each_stage(self):
+        c = SpeedConfig(speed=1.2345)
+        result = build_audio_filter(c)
+        assert "atempo=1.2345" in result
+
+
+class TestAtempoStages:
+    """atempo 多级拆分逻辑验证"""
+
+    def _extract_speeds(self, filter_str: str) -> list[float]:
+        """从 atempo 滤镜字符串中提取速度值."""
+        import re
+
+        return [float(m) for m in re.findall(r"atempo=([\d.]+)", filter_str)]
+
+    def test_product_equals_speed_fast_3x(self):
+        c = SpeedConfig(speed=3.0)
+        speeds = self._extract_speeds(build_audio_filter(c))
+        product = 1.0
+        for s in speeds:
+            product *= s
+        assert abs(product - 3.0) < 1e-4
+
+    def test_product_equals_speed_4x(self):
+        c = SpeedConfig(speed=4.0)
+        speeds = self._extract_speeds(build_audio_filter(c))
+        product = 1.0
+        for s in speeds:
+            product *= s
+        assert abs(product - 4.0) < 1e-4
+
+    def test_product_equals_speed_slow_025(self):
+        c = SpeedConfig(speed=0.25)
+        speeds = self._extract_speeds(build_audio_filter(c))
+        product = 1.0
+        for s in speeds:
+            product *= s
+        assert abs(product - 0.25) < 1e-4
+
+    def test_product_equals_speed_slow_03(self):
+        c = SpeedConfig(speed=0.3)
+        speeds = self._extract_speeds(build_audio_filter(c))
+        product = 1.0
+        for s in speeds:
+            product *= s
+        assert abs(product - 0.3) < 1e-4
+
+    def test_each_stage_in_range_fast(self):
+        c = SpeedConfig(speed=3.5)
+        speeds = self._extract_speeds(build_audio_filter(c))
+        for s in speeds:
+            assert 0.5 <= s <= 2.0
+
+    def test_each_stage_in_range_slow(self):
+        c = SpeedConfig(speed=0.35)
+        speeds = self._extract_speeds(build_audio_filter(c))
+        for s in speeds:
+            assert 0.5 <= s <= 2.0
+
+
+# ── adjust_duration ──────────────────────────────────────────────────────────
+
+
+class TestAdjustDuration:
+    """adjust_duration 时长计算"""
+
+    def test_original_speed_no_change(self):
+        assert adjust_duration(10.0, SpeedConfig(speed=1.0)) == 10.0
+
+    def test_double_speed_half_duration(self):
+        assert adjust_duration(10.0, SpeedConfig(speed=2.0)) == 5.0
+
+    def test_half_speed_double_duration(self):
+        assert adjust_duration(10.0, SpeedConfig(speed=0.5)) == 20.0
+
+    def test_zero_duration_unchanged(self):
+        assert adjust_duration(0.0, SpeedConfig(speed=2.0)) == 0.0
+
+    def test_negative_duration_unchanged(self):
+        assert adjust_duration(-1.0, SpeedConfig(speed=2.0)) == -1.0
+
+    def test_original_with_zero_duration(self):
+        assert adjust_duration(0.0, SpeedConfig(speed=1.0)) == 0.0
+
+    def test_triple_speed(self):
+        assert adjust_duration(30.0, SpeedConfig(speed=3.0)) == 10.0
+
+    def test_quarter_speed(self):
+        assert adjust_duration(10.0, SpeedConfig(speed=0.25)) == 40.0
+
+
+# ── build_clip_speed_filter ──────────────────────────────────────────────────
+
+
+class TestBuildClipSpeedFilter:
+    """build_clip_speed_filter 便捷方法"""
+
+    def test_returns_tuple_of_three(self):
+        result = build_clip_speed_filter(1.5)
+        assert len(result) == 3
+        video_filter, audio_filter, config = result
+        assert isinstance(video_filter, str)
+        assert isinstance(audio_filter, str)
+        assert isinstance(config, SpeedConfig)
+
+    def test_normal_speed(self):
+        video_filter, audio_filter, config = build_clip_speed_filter(1.0)
+        assert video_filter == ""
+        assert audio_filter == ""
+        assert config.speed == 1.0
+
+    def test_double_speed(self):
+        video_filter, audio_filter, config = build_clip_speed_filter(2.0)
+        assert "setpts" in video_filter
+        assert "atempo" in audio_filter
+        assert config.speed == 2.0
+
+    def test_clamps_speed(self):
+        _, _, config = build_clip_speed_filter(10.0)
+        assert config.speed == MAX_SPEED
+
+    def test_pitch_correct_false(self):
+        # pitch_correct=False 时仍然生成滤镜（实际使用中可能换其他算法，但接口返回不变）
+        video_filter, audio_filter, config = build_clip_speed_filter(2.0, pitch_correct=False)
+        assert config.pitch_correct is False
+        assert "setpts" in video_filter
+
+
+# ── resolve_clip_speed ───────────────────────────────────────────────────────
+
+
+class TestResolveClipSpeed:
+    """resolve_clip_speed 片段速度解析"""
+
+    def test_none_config_uses_global(self):
+        assert resolve_clip_speed(None, 1.5) == 1.5
+
+    def test_zero_speed_uses_global(self):
+        assert resolve_clip_speed({"playback_speed": 0}, 1.5) == 1.5
+
+    def test_missing_key_uses_global(self):
+        assert resolve_clip_speed({}, 2.0) == 2.0
+
+    def test_valid_speed(self):
+        assert resolve_clip_speed({"playback_speed": 1.5}, 1.0) == 1.5
+
+    def test_negative_speed_uses_global(self):
+        assert resolve_clip_speed({"playback_speed": -1.0}, 1.0) == 1.0
+
+    def test_invalid_type_uses_global(self):
+        assert resolve_clip_speed({"playback_speed": "fast"}, 1.0) == 1.0
+
+    def test_default_global_is_one(self):
+        assert resolve_clip_speed({"playback_speed": 0}) == 1.0
+
+    def test_int_speed(self):
+        result = resolve_clip_speed({"playback_speed": 2})
+        assert result == 2.0
+        assert isinstance(result, float)
+
+    def test_very_small_positive_uses_it(self):
+        # 只要 > 0 就用
+        result = resolve_clip_speed({"playback_speed": 0.1})
+        assert result == 0.1