diff --git a/apps/worker/video_processing/transition_engine.py b/apps/worker/video_processing/transition_engine.py
index 03b8409ff..069b7915e 100755
--- a/apps/worker/video_processing/transition_engine.py
+++ b/apps/worker/video_processing/transition_engine.py
@@ -12,229 +12,20 @@
 from __future__ import annotations
 
 import logging
-import sys
-from dataclasses import dataclass
-
-if sys.version_info >= (3, 11):
-    from enum import StrEnum
-else:
-    from enum import Enum
-
-    class StrEnum(str, Enum):
-        pass
-
 
+from packages.domain.transition_config import (  # noqa: F401 — 向后兼容
+    CUT_TRANSITION,
+    DEFAULT_TRANSITION_DURATION,
+    MAX_TRANSITION_DURATION,
+    MIN_TRANSITION_DURATION,
+    TransitionConfig,
+    TransitionType,
+)
 from video_processing.ffmpeg_utils import build_xfade_filter_chain
 
 logger = logging.getLogger(__name__)
 
 
-# ── 常量 ──────────────────────────────────────────────────────────────────────
-
-# 转场时长范围（秒）
-MIN_TRANSITION_DURATION = 0.3
-MAX_TRANSITION_DURATION = 2.0
-DEFAULT_TRANSITION_DURATION = 0.5
-
-# 硬切（无转场）
-CUT_TRANSITION = "cut"
-
-
-# ── 转场类型枚举 ──────────────────────────────────────────────────────────────
-
-
-class TransitionType(StrEnum):
-    """支持的转场效果类型.
-
-    每种类型对应 FFmpeg xfade filter 的一个 transition 值。
-    新增转场只需在此添加一项，并在 _FFMPEG_XFADE_MAP 中映射。
-    """
-
-    # 硬切（无转场效果，直接拼接）
-    CUT = "cut"
-
-    # 淡入淡出（最常用，默认 fallback）
-    FADE = "fade"
-
-    # 溶解（交叉溶解）
-    DISSOLVE = "dissolve"
-
-    # 滑入系列
-    SLIDE_LEFT = "slideleft"
-    SLIDE_RIGHT = "slideright"
-    SLIDE_UP = "slideup"
-    SLIDE_DOWN = "slidedown"
-
-    # 缩放
-    ZOOM = "zoom"
-
-    # 擦除系列
-    WIPE_LEFT = "wipeleft"
-    WIPE_RIGHT = "wiperight"
-    WIPE_UP = "wipeup"
-    WIPE_DOWN = "wipedown"
-
-    # 圆形扩散
-    CIRCLE_CROP = "circlecrop"
-
-    # 矩形覆盖
-    RECT_CROP = "rectcrop"
-
-    @classmethod
-    def all_supported(cls) -> list[str]:
-        """返回所有支持的转场类型名称列表."""
-        return [t.value for t in cls if t != cls.CUT]
-
-    @classmethod
-    def is_supported(cls, name: str) -> bool:
-        """检查转场类型是否支持（不区分大小写和下划线）."""
-        normalized = _normalize_transition_name(name)
-        return normalized in _NAME_TO_ENUM_MAP
-
-
-# ── 名称 → 枚举 映射（支持多种别名）──────────────────────────────────────────
-
-
-def _normalize_transition_name(name: str) -> str:
-    """标准化转场名称：小写 + 去下划线."""
-    return name.lower().replace("_", "").replace("-", "")
-
-
-# 构建别名映射
-_NAME_TO_ENUM_MAP: dict[str, TransitionType] = {}
-for _t in TransitionType:
-    _NAME_TO_ENUM_MAP[_normalize_transition_name(_t.value)] = _t
-
-# 额外的别名
-_ALIASES: dict[str, TransitionType] = {
-    "dissolve": TransitionType.DISSOLVE,
-    "crossfade": TransitionType.DISSOLVE,
-    "crossdissolve": TransitionType.DISSOLVE,
-    "fadein": TransitionType.FADE,
-    "fadeout": TransitionType.FADE,
-    "fadeblack": TransitionType.FADE,
-    "slide": TransitionType.SLIDE_LEFT,  # 默认向左滑
-    "wipe": TransitionType.WIPE_LEFT,  # 默认向左擦
-    "zoomin": TransitionType.ZOOM,
-    "zoomout": TransitionType.ZOOM,
-    "circle": TransitionType.CIRCLE_CROP,
-    "rect": TransitionType.RECT_CROP,
-}
-for _alias, _type in _ALIASES.items():
-    _key = _normalize_transition_name(_alias)
-    if _key not in _NAME_TO_ENUM_MAP:
-        _NAME_TO_ENUM_MAP[_key] = _type
-
-
-# ── TransitionType → FFmpeg xfade transition 名称映射 ─────────────────────────
-
-
-_FFMPEG_XFADE_MAP: dict[TransitionType, str] = {
-    TransitionType.FADE: "fade",
-    TransitionType.DISSOLVE: "dissolve",
-    TransitionType.SLIDE_LEFT: "slideleft",
-    TransitionType.SLIDE_RIGHT: "slideright",
-    TransitionType.SLIDE_UP: "slideup",
-    TransitionType.SLIDE_DOWN: "slidedown",
-    TransitionType.ZOOM: "zoomin",
-    TransitionType.WIPE_LEFT: "wipeleft",
-    TransitionType.WIPE_RIGHT: "wiperight",
-    TransitionType.WIPE_UP: "wipeup",
-    TransitionType.WIPE_DOWN: "wipedown",
-    TransitionType.CIRCLE_CROP: "circlecrop",
-    TransitionType.RECT_CROP: "rectcrop",
-}
-
-
-# ── 转场配置 ──────────────────────────────────────────────────────────────────
-
-
-@dataclass(slots=True)
-class TransitionConfig:
-    """转场效果配置.
-
-    Attributes:
-        effect: 转场效果名称（见 TransitionType）
-        duration: 转场时长（秒），范围 0.3~2.0，默认 0.5
-    """
-
-    effect: str = CUT_TRANSITION
-    duration: float = DEFAULT_TRANSITION_DURATION
-
-    @classmethod
-    def parse(cls, effect: str | None = None, duration: float | None = None) -> "TransitionConfig":
-        """解析并验证转场配置，自动处理边界和降级.
-
-        Args:
-            effect: 转场效果名称（None 或空则使用默认 cut）
-            duration: 转场时长（None 则使用默认值）
-
-        Returns:
-            验证后的 TransitionConfig
-        """
-        # 处理 effect
-        final_effect = CUT_TRANSITION
-        if effect and effect.strip():
-            effect_clean = effect.strip()
-            if TransitionType.is_supported(effect_clean):
-                final_effect = _resolve_transition_enum(effect_clean).value
-            elif effect_clean.lower() == CUT_TRANSITION:
-                final_effect = CUT_TRANSITION
-            else:
-                # 降级：不支持的转场 → 硬切，不阻断渲染
-                logger.warning(
-                    "不支持的转场效果 '%s'，已降级为硬切（cut）",
-                    effect_clean,
-                )
-                final_effect = CUT_TRANSITION
-
-        # 处理 duration：边界钳制
-        final_duration = DEFAULT_TRANSITION_DURATION
-        if duration is not None:
-            try:
-                d = float(duration)
-                if d < MIN_TRANSITION_DURATION:
-                    logger.warning(
-                        "转场时长 %.3fs 小于最小值 %.1fs，已钳制到最小值",
-                        d,
-                        MIN_TRANSITION_DURATION,
-                    )
-                    final_duration = MIN_TRANSITION_DURATION
-                elif d > MAX_TRANSITION_DURATION:
-                    logger.warning(
-                        "转场时长 %.3fs 大于最大值 %.1fs，已钳制到最大值",
-                        d,
-                        MAX_TRANSITION_DURATION,
-                    )
-                    final_duration = MAX_TRANSITION_DURATION
-                else:
-                    final_duration = d
-            except (TypeError, ValueError):
-                logger.warning("无效的转场时长 '%s'，使用默认值 %.1fs", duration, DEFAULT_TRANSITION_DURATION)
-                final_duration = DEFAULT_TRANSITION_DURATION
-
-        return cls(effect=final_effect, duration=final_duration)
-
-    @property
-    def is_cut(self) -> bool:
-        """是否为硬切（无转场效果）."""
-        return self.effect == CUT_TRANSITION
-
-    @property
-    def ffmpeg_transition(self) -> str:
-        """获取对应的 FFmpeg xfade transition 名称."""
-        if self.is_cut:
-            return ""
-        enum_type = _resolve_transition_enum(self.effect)
-        return _FFMPEG_XFADE_MAP.get(enum_type, "fade")
-
-
-def _resolve_transition_enum(name: str) -> TransitionType:
-    """将名称解析为 TransitionType 枚举，必须先通过 is_supported 校验."""
-    normalized = _normalize_transition_name(name)
-    return _NAME_TO_ENUM_MAP.get(normalized, TransitionType.FADE)
-
-
 # ── 转场引擎 ──────────────────────────────────────────────────────────────────
 
 
diff --git a/packages/domain/transition_config.py b/packages/domain/transition_config.py
new file mode 100755
index 000000000..3f7ee06dc
--- /dev/null
+++ b/packages/domain/transition_config.py
@@ -0,0 +1,245 @@
+"""转场配置领域模型 — 纯逻辑，无 FFmpeg 依赖.
+
+抽离自 transition_engine.py 的枚举、数据类和纯逻辑函数，
+方便单测覆盖，同时保持向后兼容。
+"""
+
+from __future__ import annotations
+
+import logging
+import sys
+from dataclasses import dataclass
+
+if sys.version_info >= (3, 11):
+    from enum import StrEnum
+else:
+    from enum import Enum
+
+    class StrEnum(str, Enum):
+        pass
+
+
+logger = logging.getLogger(__name__)
+
+
+# ── 常量 ──────────────────────────────────────────────────────────────────────
+
+# 转场时长范围（秒）
+MIN_TRANSITION_DURATION = 0.3
+MAX_TRANSITION_DURATION = 2.0
+DEFAULT_TRANSITION_DURATION = 0.5
+
+# 硬切（无转场）
+CUT_TRANSITION = "cut"
+
+
+# ── 转场类型枚举 ──────────────────────────────────────────────────────────────
+
+
+class TransitionType(StrEnum):
+    """支持的转场效果类型.
+
+    每种类型对应 FFmpeg xfade filter 的一个 transition 值。
+    """
+
+    # 硬切（无转场效果，直接拼接）
+    CUT = "cut"
+
+    # 淡入淡出（最常用，默认 fallback）
+    FADE = "fade"
+
+    # 溶解（交叉溶解）
+    DISSOLVE = "dissolve"
+
+    # 滑入系列
+    SLIDE_LEFT = "slideleft"
+    SLIDE_RIGHT = "slideright"
+    SLIDE_UP = "slideup"
+    SLIDE_DOWN = "slidedown"
+
+    # 缩放
+    ZOOM = "zoom"
+
+    # 擦除系列
+    WIPE_LEFT = "wipeleft"
+    WIPE_RIGHT = "wiperight"
+    WIPE_UP = "wipeup"
+    WIPE_DOWN = "wipedown"
+
+    # 圆形扩散
+    CIRCLE_CROP = "circlecrop"
+
+    # 矩形覆盖
+    RECT_CROP = "rectcrop"
+
+    @classmethod
+    def all_supported(cls) -> list[str]:
+        """返回所有支持的转场类型名称列表（不含 cut）."""
+        return [t.value for t in cls if t != cls.CUT]
+
+    @classmethod
+    def is_supported(cls, name: str) -> bool:
+        """检查转场类型是否支持（不区分大小写和下划线）."""
+        normalized = _normalize_transition_name(name)
+        return normalized in _NAME_TO_ENUM_MAP
+
+
+# ── 名称 → 枚举 映射（支持多种别名）──────────────────────────────────────────
+
+
+def _normalize_transition_name(name: str) -> str:
+    """标准化转场名称：小写 + 去下划线 + 去中划线."""
+    return name.lower().replace("_", "").replace("-", "")
+
+
+# 构建别名映射
+_NAME_TO_ENUM_MAP: dict[str, TransitionType] = {}
+for _t in TransitionType:
+    _NAME_TO_ENUM_MAP[_normalize_transition_name(_t.value)] = _t
+
+# 额外的别名
+_ALIASES: dict[str, TransitionType] = {
+    "dissolve": TransitionType.DISSOLVE,
+    "crossfade": TransitionType.DISSOLVE,
+    "crossdissolve": TransitionType.DISSOLVE,
+    "fadein": TransitionType.FADE,
+    "fadeout": TransitionType.FADE,
+    "fadeblack": TransitionType.FADE,
+    "slide": TransitionType.SLIDE_LEFT,  # 默认向左滑
+    "wipe": TransitionType.WIPE_LEFT,  # 默认向左擦
+    "zoomin": TransitionType.ZOOM,
+    "zoomout": TransitionType.ZOOM,
+    "circle": TransitionType.CIRCLE_CROP,
+    "rect": TransitionType.RECT_CROP,
+}
+for _alias, _type in _ALIASES.items():
+    _key = _normalize_transition_name(_alias)
+    if _key not in _NAME_TO_ENUM_MAP:
+        _NAME_TO_ENUM_MAP[_key] = _type
+
+
+# ── TransitionType → FFmpeg xfade transition 名称映射 ─────────────────────────
+
+
+_FFMPEG_XFADE_MAP: dict[TransitionType, str] = {
+    TransitionType.FADE: "fade",
+    TransitionType.DISSOLVE: "dissolve",
+    TransitionType.SLIDE_LEFT: "slideleft",
+    TransitionType.SLIDE_RIGHT: "slideright",
+    TransitionType.SLIDE_UP: "slideup",
+    TransitionType.SLIDE_DOWN: "slidedown",
+    TransitionType.ZOOM: "zoomin",
+    TransitionType.WIPE_LEFT: "wipeleft",
+    TransitionType.WIPE_RIGHT: "wiperight",
+    TransitionType.WIPE_UP: "wipeup",
+    TransitionType.WIPE_DOWN: "wipedown",
+    TransitionType.CIRCLE_CROP: "circlecrop",
+    TransitionType.RECT_CROP: "rectcrop",
+}
+
+
+def _resolve_transition_enum(name: str) -> TransitionType:
+    """将名称解析为 TransitionType 枚举，找不到则回退到 FADE."""
+    normalized = _normalize_transition_name(name)
+    return _NAME_TO_ENUM_MAP.get(normalized, TransitionType.FADE)
+
+
+# ── 转场配置 ──────────────────────────────────────────────────────────────────
+
+
+@dataclass(slots=True)
+class TransitionConfig:
+    """转场效果配置.
+
+    Attributes:
+        effect: 转场效果名称（见 TransitionType）
+        duration: 转场时长（秒），范围 0.3~2.0，默认 0.5
+    """
+
+    effect: str = CUT_TRANSITION
+    duration: float = DEFAULT_TRANSITION_DURATION
+
+    @classmethod
+    def parse(
+        cls,
+        effect: str | None = None,
+        duration: float | None = None,
+    ) -> "TransitionConfig":
+        """解析并验证转场配置，自动处理边界和降级.
+
+        Args:
+            effect: 转场效果名称（None 或空则使用默认 cut）
+            duration: 转场时长（None 则使用默认值）
+
+        Returns:
+            验证后的 TransitionConfig
+        """
+        # 处理 effect
+        final_effect = CUT_TRANSITION
+        if effect and effect.strip():
+            effect_clean = effect.strip()
+            if TransitionType.is_supported(effect_clean):
+                final_effect = _resolve_transition_enum(effect_clean).value
+            elif effect_clean.lower() == CUT_TRANSITION:
+                final_effect = CUT_TRANSITION
+            else:
+                # 降级：不支持的转场 → 硬切，不阻断渲染
+                logger.warning(
+                    "不支持的转场效果 '%s'，已降级为硬切（cut）",
+                    effect_clean,
+                )
+                final_effect = CUT_TRANSITION
+
+        # 处理 duration：边界钳制
+        final_duration = DEFAULT_TRANSITION_DURATION
+        if duration is not None:
+            try:
+                d = float(duration)
+                if d < MIN_TRANSITION_DURATION:
+                    logger.warning(
+                        "转场时长 %.3fs 小于最小值 %.1fs，已钳制到最小值",
+                        d,
+                        MIN_TRANSITION_DURATION,
+                    )
+                    final_duration = MIN_TRANSITION_DURATION
+                elif d > MAX_TRANSITION_DURATION:
+                    logger.warning(
+                        "转场时长 %.3fs 大于最大值 %.1fs，已钳制到最大值",
+                        d,
+                        MAX_TRANSITION_DURATION,
+                    )
+                    final_duration = MAX_TRANSITION_DURATION
+                else:
+                    final_duration = d
+            except (TypeError, ValueError):
+                logger.warning(
+                    "无效的转场时长 '%s'，使用默认值 %.1fs",
+                    duration,
+                    DEFAULT_TRANSITION_DURATION,
+                )
+                final_duration = DEFAULT_TRANSITION_DURATION
+
+        return cls(effect=final_effect, duration=final_duration)
+
+    @property
+    def is_cut(self) -> bool:
+        """是否为硬切（无转场效果）."""
+        return self.effect == CUT_TRANSITION
+
+    @property
+    def ffmpeg_transition(self) -> str:
+        """获取对应的 FFmpeg xfade transition 名称."""
+        if self.is_cut:
+            return ""
+        enum_type = _resolve_transition_enum(self.effect)
+        return _FFMPEG_XFADE_MAP.get(enum_type, "fade")
+
+    def validate(self) -> tuple[bool, str]:
+        """校验配置合法性，返回 (是否合法, 错误信息)."""
+        if self.duration < MIN_TRANSITION_DURATION:
+            return False, f"duration不能小于{MIN_TRANSITION_DURATION}s"
+        if self.duration > MAX_TRANSITION_DURATION:
+            return False, f"duration不能大于{MAX_TRANSITION_DURATION}s"
+        if not self.is_cut and not TransitionType.is_supported(self.effect):
+            return False, f"不支持的转场效果: {self.effect}"
+        return True, ""
diff --git a/tests/unit/test_transition_config.py b/tests/unit/test_transition_config.py
new file mode 100755
index 000000000..5cb7139fb
--- /dev/null
+++ b/tests/unit/test_transition_config.py
@@ -0,0 +1,276 @@
+"""transition_config 模块单测 — 纯逻辑，无 FFmpeg 依赖."""
+
+from __future__ import annotations
+
+import pytest
+
+from packages.domain.transition_config import (
+    CUT_TRANSITION,
+    DEFAULT_TRANSITION_DURATION,
+    MAX_TRANSITION_DURATION,
+    MIN_TRANSITION_DURATION,
+    TransitionConfig,
+    TransitionType,
+)
+
+# ── 常量 ──────────────────────────────────────────────────────────────────────
+
+
+class TestConstants:
+    def test_duration_bounds(self):
+        assert MIN_TRANSITION_DURATION == 0.3
+        assert MAX_TRANSITION_DURATION == 2.0
+        assert DEFAULT_TRANSITION_DURATION == 0.5
+        assert MIN_TRANSITION_DURATION < DEFAULT_TRANSITION_DURATION < MAX_TRANSITION_DURATION
+
+    def test_cut_transition(self):
+        assert CUT_TRANSITION == "cut"
+
+
+# ── TransitionType 枚举 ──────────────────────────────────────────────────────
+
+
+class TestTransitionType:
+    def test_all_supported_includes_all_except_cut(self):
+        supported = TransitionType.all_supported()
+        assert "cut" not in supported
+        assert "fade" in supported
+        assert "dissolve" in supported
+        assert len(supported) >= 10  # 至少有10种转场
+
+    def test_all_supported_unique(self):
+        supported = TransitionType.all_supported()
+        assert len(supported) == len(set(supported))
+
+    def test_is_supported_exact_match(self):
+        assert TransitionType.is_supported("fade") is True
+        assert TransitionType.is_supported("dissolve") is True
+        assert TransitionType.is_supported("slideleft") is True
+
+    def test_is_supported_case_insensitive(self):
+        assert TransitionType.is_supported("FADE") is True
+        assert TransitionType.is_supported("Fade") is True
+        assert TransitionType.is_supported("SlideLeft") is True
+
+    def test_is_supported_with_underscores(self):
+        assert TransitionType.is_supported("slide_left") is True
+        assert TransitionType.is_supported("wipe_right") is True
+        assert TransitionType.is_supported("circle_crop") is True
+
+    def test_is_supported_with_hyphens(self):
+        assert TransitionType.is_supported("slide-left") is True
+        assert TransitionType.is_supported("wipe-down") is True
+
+    def test_is_supported_aliases(self):
+        assert TransitionType.is_supported("crossfade") is True
+        assert TransitionType.is_supported("crossdissolve") is True
+        assert TransitionType.is_supported("fadein") is True
+        assert TransitionType.is_supported("fadeout") is True
+        assert TransitionType.is_supported("slide") is True
+        assert TransitionType.is_supported("wipe") is True
+        assert TransitionType.is_supported("zoomin") is True
+        assert TransitionType.is_supported("zoomout") is True
+        assert TransitionType.is_supported("circle") is True
+        assert TransitionType.is_supported("rect") is True
+
+    def test_is_supported_unknown(self):
+        assert TransitionType.is_supported("unknown_effect") is False
+        assert TransitionType.is_supported("") is False
+        assert TransitionType.is_supported("12345") is False
+
+    def test_enum_values_match_ffmpeg(self):
+        # 枚举值应该就是 ffmpeg xfade 的 transition 名
+        assert TransitionType.FADE.value == "fade"
+        assert TransitionType.DISSOLVE.value == "dissolve"
+        assert TransitionType.SLIDE_LEFT.value == "slideleft"
+        assert TransitionType.CUT.value == "cut"
+
+
+# ── TransitionConfig 默认值 ──────────────────────────────────────────────────
+
+
+class TestTransitionConfigDefaults:
+    def test_default_config(self):
+        cfg = TransitionConfig()
+        assert cfg.effect == CUT_TRANSITION
+        assert cfg.duration == DEFAULT_TRANSITION_DURATION
+        assert cfg.is_cut is True
+
+    def test_is_cut_true(self):
+        cfg = TransitionConfig(effect="cut")
+        assert cfg.is_cut is True
+
+    def test_is_cut_false(self):
+        cfg = TransitionConfig(effect="fade")
+        assert cfg.is_cut is False
+
+
+# ── TransitionConfig.parse ───────────────────────────────────────────────────
+
+
+class TestTransitionConfigParse:
+    def test_none_params_default(self):
+        cfg = TransitionConfig.parse()
+        assert cfg.effect == CUT_TRANSITION
+        assert cfg.duration == DEFAULT_TRANSITION_DURATION
+
+    def test_empty_effect_default(self):
+        cfg = TransitionConfig.parse(effect="")
+        assert cfg.effect == CUT_TRANSITION
+
+    def test_whitespace_effect_default(self):
+        cfg = TransitionConfig.parse(effect="   ")
+        assert cfg.effect == CUT_TRANSITION
+
+    def test_valid_effect_fade(self):
+        cfg = TransitionConfig.parse(effect="fade")
+        assert cfg.effect == "fade"
+        assert cfg.is_cut is False
+
+    def test_valid_effect_case_insensitive(self):
+        cfg = TransitionConfig.parse(effect="FADE")
+        assert cfg.effect == "fade"
+
+    def test_valid_effect_with_underscores(self):
+        cfg = TransitionConfig.parse(effect="slide_left")
+        assert cfg.effect == "slideleft"
+
+    def test_alias_effect(self):
+        cfg = TransitionConfig.parse(effect="crossfade")
+        assert cfg.effect == "dissolve"  # 别名映射到 dissolve
+
+    def test_unknown_effect_falls_back_to_cut(self):
+        cfg = TransitionConfig.parse(effect="magic_sparkles")
+        assert cfg.effect == CUT_TRANSITION
+        assert cfg.is_cut is True
+
+    def test_cut_effect_stays_cut(self):
+        cfg = TransitionConfig.parse(effect="cut")
+        assert cfg.effect == CUT_TRANSITION
+
+    def test_cut_effect_case_insensitive(self):
+        cfg = TransitionConfig.parse(effect="CUT")
+        assert cfg.effect == CUT_TRANSITION
+
+    def test_duration_default(self):
+        cfg = TransitionConfig.parse(duration=None)
+        assert cfg.duration == DEFAULT_TRANSITION_DURATION
+
+    def test_duration_within_range(self):
+        cfg = TransitionConfig.parse(duration=1.0)
+        assert cfg.duration == 1.0
+
+    def test_duration_at_min(self):
+        cfg = TransitionConfig.parse(duration=MIN_TRANSITION_DURATION)
+        assert cfg.duration == MIN_TRANSITION_DURATION
+
+    def test_duration_at_max(self):
+        cfg = TransitionConfig.parse(duration=MAX_TRANSITION_DURATION)
+        assert cfg.duration == MAX_TRANSITION_DURATION
+
+    def test_duration_below_min_clamped(self):
+        cfg = TransitionConfig.parse(duration=0.1)
+        assert cfg.duration == MIN_TRANSITION_DURATION
+
+    def test_duration_above_max_clamped(self):
+        cfg = TransitionConfig.parse(duration=3.0)
+        assert cfg.duration == MAX_TRANSITION_DURATION
+
+    def test_duration_zero_clamped(self):
+        cfg = TransitionConfig.parse(duration=0)
+        assert cfg.duration == MIN_TRANSITION_DURATION
+
+    def test_duration_negative_clamped(self):
+        cfg = TransitionConfig.parse(duration=-1.0)
+        assert cfg.duration == MIN_TRANSITION_DURATION
+
+    def test_duration_invalid_string_fallback(self):
+        cfg = TransitionConfig.parse(duration="bad")  # type: ignore[arg-type]
+        assert cfg.duration == DEFAULT_TRANSITION_DURATION
+
+    def test_duration_numeric_string(self):
+        cfg = TransitionConfig.parse(duration="1.5")  # type: ignore[arg-type]
+        assert cfg.duration == 1.5
+
+    def test_full_parse(self):
+        cfg = TransitionConfig.parse(effect="wipe_up", duration=1.2)
+        assert cfg.effect == "wipeup"
+        assert cfg.duration == 1.2
+        assert cfg.is_cut is False
+
+
+# ── TransitionConfig.ffmpeg_transition ───────────────────────────────────────
+
+
+class TestFfmpegTransition:
+    def test_cut_returns_empty(self):
+        cfg = TransitionConfig(effect="cut")
+        assert cfg.ffmpeg_transition == ""
+
+    def test_fade_matches(self):
+        cfg = TransitionConfig(effect="fade")
+        assert cfg.ffmpeg_transition == "fade"
+
+    def test_dissolve_matches(self):
+        cfg = TransitionConfig(effect="dissolve")
+        assert cfg.ffmpeg_transition == "dissolve"
+
+    def test_slide_left_matches(self):
+        cfg = TransitionConfig(effect="slideleft")
+        assert cfg.ffmpeg_transition == "slideleft"
+
+    def test_wipe_down_matches(self):
+        cfg = TransitionConfig(effect="wipedown")
+        assert cfg.ffmpeg_transition == "wipedown"
+
+    def test_zoom_matches_zoomin(self):
+        cfg = TransitionConfig(effect="zoom")
+        assert cfg.ffmpeg_transition == "zoomin"
+
+    def test_circle_crop_matches(self):
+        cfg = TransitionConfig(effect="circlecrop")
+        assert cfg.ffmpeg_transition == "circlecrop"
+
+
+# ── TransitionConfig.validate ────────────────────────────────────────────────
+
+
+class TestTransitionConfigValidate:
+    def test_valid_cut(self):
+        cfg = TransitionConfig(effect="cut", duration=0.5)
+        ok, err = cfg.validate()
+        assert ok is True
+        assert err == ""
+
+    def test_valid_fade(self):
+        cfg = TransitionConfig(effect="fade", duration=1.0)
+        ok, err = cfg.validate()
+        assert ok is True
+
+    def test_duration_below_min_invalid(self):
+        cfg = TransitionConfig(effect="fade", duration=0.1)
+        ok, err = cfg.validate()
+        assert ok is False
+        assert "duration" in err
+
+    def test_duration_above_max_invalid(self):
+        cfg = TransitionConfig(effect="fade", duration=3.0)
+        ok, err = cfg.validate()
+        assert ok is False
+        assert "duration" in err
+
+    def test_unsupported_effect_invalid(self):
+        cfg = TransitionConfig(effect="unknown", duration=0.5)
+        ok, err = cfg.validate()
+        assert ok is False
+        assert "不支持的转场" in err
+
+    def test_min_duration_boundary_valid(self):
+        cfg = TransitionConfig(effect="fade", duration=MIN_TRANSITION_DURATION)
+        ok, _ = cfg.validate()
+        assert ok is True
+
+    def test_max_duration_boundary_valid(self):
+        cfg = TransitionConfig(effect="fade", duration=MAX_TRANSITION_DURATION)
+        ok, _ = cfg.validate()
+        assert ok is True