diff --git a/packages/domain/hms_domain/__init__.py b/packages/domain/hms_domain/__init__.py
index 23b9f50..631f444 100644
--- a/packages/domain/hms_domain/__init__.py
+++ b/packages/domain/hms_domain/__init__.py
@@ -2,6 +2,29 @@
 
 from hms_domain.identity import NodeIdentity, NodeRole
 from hms_domain.ids import new_node_id, new_uuid, persistent_node_id
+from hms_domain.model import (
+    DOMAIN_SCHEMA_VERSION,
+    BlendMode,
+    ColorControls,
+    ColorSpace,
+    Composition,
+    Crop,
+    EffectInstance,
+    EffectScope,
+    Layer,
+    LayerType,
+    LoopMode,
+    MediaAsset,
+    OutputSurface,
+    PresetScene,
+    Project,
+    QualityMode,
+    Source,
+    SourceType,
+    Transform2D,
+    TransitionType,
+    TransportState,
+)
 
 __all__ = [
     "new_uuid",
@@ -9,4 +32,25 @@ __all__ = [
     "persistent_node_id",
     "NodeIdentity",
     "NodeRole",
+    "DOMAIN_SCHEMA_VERSION",
+    "Project",
+    "Composition",
+    "Layer",
+    "LayerType",
+    "Source",
+    "SourceType",
+    "EffectInstance",
+    "EffectScope",
+    "BlendMode",
+    "Transform2D",
+    "Crop",
+    "ColorControls",
+    "ColorSpace",
+    "LoopMode",
+    "TransportState",
+    "QualityMode",
+    "MediaAsset",
+    "OutputSurface",
+    "PresetScene",
+    "TransitionType",
 ]
diff --git a/packages/domain/hms_domain/model.py b/packages/domain/hms_domain/model.py
new file mode 100644
index 0000000..0550de4
--- /dev/null
+++ b/packages/domain/hms_domain/model.py
@@ -0,0 +1,452 @@
+"""Domänenmodell (PLAN.md §10.1, §12.3, §13.2).
+
+Alle Modelle sind plattformneutral (Pydantic) und werden sowohl für
+Persistenz als auch API/IPC verwendet (§10). Sie enthalten keinerlei
+D3D11-/HLSL-/OpenGL-/GLSL-Typen (§12.6).
+
+Regeln:
+- stabile UUIDs für alle Objekte (§3.6)
+- Parameter werden über stabile Pfade adressiert, nie über Namen (§10.2)
+- Layer-Reihenfolge = Z-Reihenfolge, eindeutig und lückenlos
+- zwei Effekt-Slots je Layer im MVP (§4.1)
+- Blend-Modi V1 fest definiert (§12.4)
+- Schema-Version für Migrationen (§24.4)
+"""
+
+from __future__ import annotations
+
+import uuid
+from datetime import UTC, datetime
+from enum import StrEnum
+from pathlib import PurePosixPath
+
+from pydantic import BaseModel, ConfigDict, Field, field_validator, model_validator
+
+DOMAIN_SCHEMA_VERSION = 1
+
+
+def _now() -> str:
+    return datetime.now(UTC).isoformat()
+
+
+def _new_uuid() -> str:
+    return str(uuid.uuid4())
+
+
+class LayerType(StrEnum):
+    """Layer-Typen V1 (§12.3). Media/Generator/Adjustment/Group."""
+
+    MEDIA = "media"
+    IMAGE = "image"
+    SOLID = "solid"
+    GENERATOR = "generator"
+    ADJUSTMENT = "adjustment"
+    GROUP = "group"
+
+
+class BlendMode(StrEnum):
+    """Blend-Modi V1 (§12.4) – mit Golden-Image-Tests zu prüfen."""
+
+    NORMAL = "normal"
+    ADD = "add"
+    MULTIPLY = "multiply"
+    SCREEN = "screen"
+    LIGHTEN = "lighten"
+    DARKEN = "darken"
+    DIFFERENCE = "difference"
+    OVERLAY = "overlay"
+    ALPHA_PREMULTIPLIED = "alpha_premultiplied"
+
+
+class SourceType(StrEnum):
+    """Quelltypen V1 (§12.3 Media Layer + Generator Layer)."""
+
+    VIDEO = "video"
+    IMAGE = "image"
+    SOLID = "solid"
+    GENERATOR = "generator"
+
+
+class LoopMode(StrEnum):
+    """Playback-Loop (§12.5). Ping-Pong nur wenn technisch unterstützt."""
+
+    ONCE = "once"
+    LOOP = "loop"
+    PING_PONG = "ping_pong"
+
+
+class TransportState(StrEnum):
+    """Transportzustand einer Quelle (§12.5)."""
+
+    STOPPED = "stopped"
+    PLAYING = "playing"
+    PAUSED = "paused"
+
+
+class ColorSpace(StrEnum):
+    COLOR_SRGB = "sRGB"
+    LINEAR = "linear"
+
+
+class EffectScope(StrEnum):
+    """Instanzierbare Scopes für Filter (§14.8). V1: Layer/Group/Master."""
+
+    SOURCE = "source"
+    LAYER = "layer"
+    GROUP = "group"
+    MASTER = "master"
+    OUTPUT = "output"
+
+
+class QualityMode(StrEnum):
+    """Auto Quality oder feste Stufe (§14.8)."""
+
+    AUTO = "auto"
+    FIXED = "fixed"
+
+
+# ---------- Transformation (2D, §10.1 Layer) ----------
+
+
+class Transform2D(BaseModel):
+    """Feste 2D-Transformation je Layer (§10.1).
+
+    position_x/y und anchor in normalisierten Canvas-Koordinaten (-1..1
+    relativ zur Canvas-Mitte), rotation in Grad, scale um Anchor.
+    Zusätzliche Transformeffekte stehen zusätzlich in der Effektkette
+    (§15.2 Transform2D-Effekt).
+    """
+
+    position_x: float = 0.0
+    position_y: float = 0.0
+    anchor_x: float = 0.5
+    anchor_y: float = 0.5
+    scale_x: float = 1.0
+    scale_y: float = 1.0
+    rotation_deg: float = 0.0
+
+
+# ---------- Crop (§10.1) ----------
+
+
+class Crop(BaseModel):
+    """Beschnitt je Seite, normalisiert 0..1."""
+
+    left: float = Field(default=0.0, ge=0.0, le=1.0)
+    right: float = Field(default=0.0, ge=0.0, le=1.0)
+    top: float = Field(default=0.0, ge=0.0, le=1.0)
+    bottom: float = Field(default=0.0, ge=0.0, le=1.0)
+
+
+# ---------- Farbsteuerung (§10.1 color_controls) ----------
+
+
+class ColorControls(BaseModel):
+    """Layer-Farbregler (Layer64-Kanäle 37–40, §16.4)."""
+
+    hue: float = Field(default=0.0, ge=-0.5, le=0.5)
+    saturation: float = Field(default=1.0, ge=0.0, le=2.0)
+    brightness: float = Field(default=1.0, ge=0.0, le=2.0)
+    contrast: float = Field(default=1.0, ge=0.0, le=2.0)
+
+
+# ---------- Quelle (§10.1 Source) ----------
+
+
+class Source(BaseModel):
+    """Medien-/Generator-Quelle eines Layers (§10.1).
+
+    - plugin_id/plugin_version: versionierter Plugin-Vertrag (§14)
+    - asset_id: stabile UUID des MediaAsset, nie ein Pfad (§13.2)
+    - in_point/out_point: normalisiert 0..1 (§12.5)
+    - speed: 1.0 = Normalwiedergabe; Reverse nur wenn Medium geeignet (§12.5)
+    """
+
+    plugin_id: str
+    plugin_version: str = "1.0.0"
+    source_type: SourceType
+    asset_id: str | None = None
+    parameters: dict[str, float] = Field(default_factory=dict)
+    playback_state: TransportState = TransportState.STOPPED
+    in_point: float = Field(default=0.0, ge=0.0, le=1.0)
+    out_point: float = Field(default=1.0, ge=0.0, le=1.0)
+    loop_mode: LoopMode = LoopMode.LOOP
+    speed: float = Field(default=1.0, ge=-4.0, le=4.0)
+    volume: float = Field(default=1.0, ge=0.0, le=1.0)
+    audio_enabled: bool = True
+
+    @model_validator(mode="after")
+    def _validate_points(self) -> Source:
+        if self.in_point >= self.out_point:
+            raise ValueError("in_point muss kleiner als out_point sein")
+        if self.source_type in (SourceType.VIDEO, SourceType.IMAGE) and not self.asset_id:
+            raise ValueError("Medien-Quellen benötigen ein asset_id")
+        return self
+
+
+# ---------- Effektinstanz (§10.1 EffectInstance) ----------
+
+
+class EffectInstance(BaseModel):
+    """Effektinstanz mit unverändertem Effektvertrag (§14.8).
+
+    - mix 0 bypassed kostengünstig (§15.3)
+    - requested_quality persistiert; resolved_quality ist Laufzeitzustand
+      und wird nicht persistiert
+    - bypass_on_error: Pluginfehler überbrücken, Layer bleibt aktiv (§12.2)
+    """
+
+    id: str = Field(default_factory=_new_uuid)
+    plugin_id: str
+    plugin_version: str = "1.0.0"
+    scope: EffectScope = EffectScope.LAYER
+    order_index: int = 0
+    enabled: bool = True
+    mix: float = Field(default=1.0, ge=0.0, le=1.0)
+    effect_blend_mode: BlendMode = BlendMode.NORMAL
+    parameters: dict[str, float] = Field(default_factory=dict)
+    preset_id: str | None = None
+    quality_mode: QualityMode = QualityMode.AUTO
+    requested_quality: str = "auto"
+    bypass_on_error: bool = True
+
+
+# ---------- Layer (§10.1 Layer) ----------
+
+
+class Layer(BaseModel):
+    """Layer einer Composition (§10.1).
+
+    z_index: eindeutige Z-Reihenfolge; 0 = unten (§10.1 „layers[] in
+    eindeutiger Z-Reihenfolge"). 8 gleichzeitig patchbare Layer im MVP
+    (§4.1); maximal 64 werden schema-seitig zugelassen.
+    """
+
+    model_config = ConfigDict(validate_assignment=True)
+
+    id: str = Field(default_factory=_new_uuid)
+    name: str = "Layer"
+    enabled: bool = True
+    layer_type: LayerType
+    source: Source | None = None
+    opacity: float = Field(default=1.0, ge=0.0, le=1.0)
+    blend_mode: BlendMode = BlendMode.NORMAL
+    transform: Transform2D = Field(default_factory=Transform2D)
+    crop: Crop = Field(default_factory=Crop)
+    color_controls: ColorControls = Field(default_factory=ColorControls)
+    effects: list[EffectInstance] = Field(default_factory=list)
+    mask_id: str | None = None
+    target_group_id: str | None = None
+    dmx_patch_id: str | None = None
+
+    @field_validator("effects")
+    @classmethod
+    def _max_two_effect_slots(cls, v: list[EffectInstance]) -> list[EffectInstance]:
+        if len(v) > 2:
+            raise ValueError("maximal zwei Effekt-Slots je Layer im MVP (§4.1)")
+        order = [e.order_index for e in v]
+        if len(order) != len(set(order)):
+            raise ValueError("order_index muss eindeutig sein (§14.8)")
+        return v
+
+    @model_validator(mode="after")
+    def _type_source_consistency(self) -> Layer:
+        media_types = (
+            LayerType.MEDIA,
+            LayerType.IMAGE,
+            LayerType.SOLID,
+            LayerType.GENERATOR,
+        )
+        if self.layer_type in media_types:
+            if self.source is None:
+                raise ValueError("Layer dieses Typs benötigen eine Quelle")
+        if self.layer_type in (LayerType.ADJUSTMENT, LayerType.GROUP) and self.source is not None:
+            raise ValueError("Adjustment-/Group-Layer besitzen keine eigene Quelle")
+        return self
+
+
+# ---------- Composition (§10.1) ----------
+
+
+class Composition(BaseModel):
+    """Master-Canvas-Definition (§10.1).
+
+    - width/height: virtuelle Canvas (Desktop bis 3840×2160, §3.3)
+    - fps: feste Master-Bildrate (§12.2)
+    - layers: eindeutige Z-Reihenfolge, unten = 0
+    """
+
+    model_config = ConfigDict(validate_assignment=True)
+
+    id: str = Field(default_factory=_new_uuid)
+    name: str = "Composition"
+    width: int = Field(default=1920, ge=16, le=8192)
+    height: int = Field(default=1080, ge=16, le=8192)
+    fps: float = Field(default=60.0, gt=0.0, le=240.0)
+    color_space: ColorSpace = ColorSpace.COLOR_SRGB
+    background_color: str = "#000000"
+    duration: float | None = None
+    layers: list[Layer] = Field(default_factory=list)
+
+    @field_validator("layers")
+    @classmethod
+    def _unique_z_order(cls, v: list[Layer]) -> list[Layer]:
+        ids = [layer.id for layer in v]
+        if len(ids) != len(set(ids)):
+            raise ValueError("Layer-IDs müssen eindeutig sein")
+        if len(v) > 64:
+            raise ValueError("maximal 64 Layer je Composition")
+        return v
+
+    def layer_by_id(self, layer_id: str) -> Layer | None:
+        return next((layer for layer in self.layers if layer.id == layer_id), None)
+
+    def sorted_layers(self) -> list[Layer]:
+        """Render-Reihenfolge: unten zuerst (Z aufsteigend über Listenposition)."""
+        return list(self.layers)
+
+
+# ---------- MediaAsset (§13.2) ----------
+
+
+class MediaAsset(BaseModel):
+    """Medienasset (§13.2): stabile UUID + relativer portabler Pfad.
+
+    - rel_path: relativ zum Projekt-/Media-Root, POSIX-Notation (§9.1:
+      keine Laufwerksbuchstaben, keine absoluten Pfade)
+    - content_hash: bei Projektpaketen verpflichtend (§13.2)
+    - seek_suitability: dokumentierte Eignung für Seek/Reverse (§12.5);
+      ungeprüft = unknown, niemals optimistisch
+    """
+
+    id: str = Field(default_factory=_new_uuid)
+    rel_path: str
+    file_size_bytes: int = Field(default=0, ge=0)
+    mtime_ns: int = 0
+    content_hash: str | None = None
+    container: str | None = None
+    video_codec: str | None = None
+    audio_codec: str | None = None
+    width: int | None = None
+    height: int | None = None
+    fps: float | None = None
+    duration_s: float | None = None
+    has_alpha: bool = False
+    audio_streams: int = 0
+    thumbnail_rel_path: str | None = None
+    proxy_rel_path: str | None = None
+    seek_suitability: str = "unknown"  # unknown|fast_seek|slow_seek|unsuitable
+    analysis_state: str = "pending"  # pending|running|done|failed
+
+    @field_validator("rel_path")
+    @classmethod
+    def _portable_relative_path(cls, v: str) -> str:
+        p = PurePosixPath(v)
+        if p.is_absolute() or ".." in p.parts:
+            raise ValueError(f"rel_path muss portabel-relativ sein: {v!r} (§9.1)")
+        if not v:
+            raise ValueError("rel_path darf nicht leer sein")
+        return v
+
+
+# ---------- OutputSurface (§10.1, §22.2) ----------
+
+
+class OutputSurface(BaseModel):
+    """Physische/Logische Ausgabefläche (§10.1 OutputSurface, §22.2).
+
+    Das Mapping-Datenmodell ist ab V1 vorhanden (§22.1), auch wenn der
+    vollständige Mapping-Editor später folgt.
+    """
+
+    id: str = Field(default_factory=_new_uuid)
+    node_id: str
+    display_id: str = ""
+    enabled: bool = True
+    width: int = Field(default=1920, ge=16, le=8192)
+    height: int = Field(default=1080, ge=16, le=8192)
+    refresh_rate_hz: float = Field(default=60.0, gt=0.0)
+    # Canvas-Ausschnitt (§22.2): Quellrechteck in normalisierten Koordinaten
+    slice_x: float = Field(default=0.0, ge=0.0, le=1.0)
+    slice_y: float = Field(default=0.0, ge=0.0, le=1.0)
+    slice_w: float = Field(default=1.0, ge=0.0, le=1.0)
+    slice_h: float = Field(default=1.0, ge=0.0, le=1.0)
+    destination_x: int = 0
+    destination_y: int = 0
+    rotation_deg: float = 0.0
+    flip_horizontal: bool = False
+    flip_vertical: bool = False
+    test_pattern: int = 0  # 0 = aus; Enum folgt mit Mapping-Phase
+    fallback_policy: str = "hold_last_frame"  # §26.1
+
+
+# ---------- PresetScene (§18.1) ----------
+
+
+class TransitionType(StrEnum):
+    """Preset-Übergänge V1 (§18.3)."""
+
+    CUT = "cut"
+    CROSSFADE = "crossfade"
+    DIP_TO_BLACK = "dip_to_black"
+    WIPE_HORIZONTAL = "wipe_horizontal"
+    WIPE_VERTICAL = "wipe_vertical"
+    LUMA_FADE = "luma_fade"
+    PLUGIN = "plugin"
+
+
+class PresetScene(BaseModel):
+    """Szene/Preset: normalisierter Composition-Snapshot (§18.1).
+
+    Empfehlung §18.1: intern normalisierter Snapshot mit deduplizierten
+    Asset-/Plugin-Referenzen; Übergänge berechnen den Diff zur Laufzeit.
+    """
+
+    id: str = Field(default_factory=_new_uuid)
+    name: str
+    composition_snapshot: dict  # normalisiertes Composition-Serialisat
+    transition_type: TransitionType = TransitionType.CUT
+    transition_duration_s: float = Field(default=0.0, ge=0.0, le=60.0)
+    preload_hints: list[str] = Field(default_factory=list)  # asset_ids
+
+
+# ---------- Project (§10.1) ----------
+
+
+class Project(BaseModel):
+    """Projekt (§10.1) mit schema_version für Migrationen (§24.4)."""
+
+    model_config = ConfigDict(validate_assignment=True)
+
+    schema_version: int = DOMAIN_SCHEMA_VERSION
+    id: str = Field(default_factory=_new_uuid)
+    name: str = "Neues Projekt"
+    created_at: str = Field(default_factory=_now)
+    updated_at: str = Field(default_factory=_now)
+    settings: dict = Field(default_factory=dict)
+    media_assets: list[MediaAsset] = Field(default_factory=list)
+    compositions: list[Composition] = Field(default_factory=list)
+    scenes: list[PresetScene] = Field(default_factory=list)
+    timelines: list[dict] = Field(default_factory=list)  # Phase 6+ (§19)
+    outputs: list[OutputSurface] = Field(default_factory=list)
+    control_bindings: list[dict] = Field(default_factory=list)
+    audio_profiles: list[dict] = Field(default_factory=list)
+    automation_policies: list[dict] = Field(default_factory=list)
+    plugin_requirements: list[dict] = Field(default_factory=list)
+
+    @field_validator("media_assets")
+    @classmethod
+    def _unique_asset_ids(cls, v: list[MediaAsset]) -> list[MediaAsset]:
+        ids = [a.id for a in v]
+        if len(ids) != len(set(ids)):
+            raise ValueError("MediaAsset-IDs müssen eindeutig sein")
+        paths = [a.rel_path for a in v]
+        if len(paths) != len(set(paths)):
+            raise ValueError("MediaAsset-Pfade müssen eindeutig sein (§13.3 Duplikate)")
+        return v
+
+    def composition_by_id(self, composition_id: str) -> Composition | None:
+        return next((c for c in self.compositions if c.id == composition_id), None)
+
+    def asset_by_id(self, asset_id: str) -> MediaAsset | None:
+        return next((a for a in self.media_assets if a.id == asset_id), None)
diff --git a/tests/unit/test_domain_model.py b/tests/unit/test_domain_model.py
new file mode 100644
index 0000000..3a477fa
--- /dev/null
+++ b/tests/unit/test_domain_model.py
@@ -0,0 +1,249 @@
+"""Unit-Tests Domänenmodell (PLAN.md §10.1, §12, §13.2, §18.1)."""
+
+from __future__ import annotations
+
+import pytest
+from hms_domain import (
+    BlendMode,
+    Composition,
+    EffectInstance,
+    Layer,
+    LayerType,
+    MediaAsset,
+    OutputSurface,
+    PresetScene,
+    Project,
+    Source,
+    SourceType,
+    TransitionType,
+)
+from pydantic import ValidationError
+
+
+def _media_source(asset_id: str | None = None) -> Source:
+    return Source(
+        plugin_id="hms.source.video",
+        source_type=SourceType.VIDEO,
+        asset_id=asset_id or "00000000-0000-0000-0000-000000000001",
+    )
+
+
+def _generator_source() -> Source:
+    return Source(
+        plugin_id="hms.generator.solid",
+        source_type=SourceType.GENERATOR,
+    )
+
+
+def _media_layer(**overrides) -> Layer:
+    defaults = dict(name="Video A", layer_type=LayerType.MEDIA, source=_media_source())
+    defaults.update(overrides)
+    return Layer(**defaults)
+
+
+# ---------- Source (§10.1, §12.5) ----------
+
+
+def test_media_source_requires_asset() -> None:
+    with pytest.raises(ValidationError, match="asset_id"):
+        Source(plugin_id="hms.source.video", source_type=SourceType.VIDEO)
+
+
+def test_generator_source_needs_no_asset() -> None:
+    src = _generator_source()
+    assert src.asset_id is None
+    assert src.speed == 1.0
+
+
+def test_in_point_must_be_before_out_point() -> None:
+    with pytest.raises(ValidationError, match="in_point"):
+        Source(
+            plugin_id="hms.source.video",
+            source_type=SourceType.VIDEO,
+            asset_id="00000000-0000-0000-0000-000000000001",
+            in_point=0.8,
+            out_point=0.2,
+        )
+
+
+def test_speed_bounds_per_plan() -> None:
+    """§16.6: bis maximal 4x, negative Geschwindigkeit zugelassen."""
+    src = _media_source()
+    assert src.speed == 1.0
+    with pytest.raises(ValidationError):
+        Source(
+            plugin_id="hms.source.video",
+            source_type=SourceType.VIDEO,
+            asset_id="00000000-0000-0000-0000-000000000001",
+            speed=8.0,
+        )
+
+
+# ---------- Layer (§10.1, §4.1, §12.3) ----------
+
+
+def test_media_layer_defaults() -> None:
+    layer = _media_layer()
+    assert layer.opacity == 1.0
+    assert layer.blend_mode is BlendMode.NORMAL
+    assert layer.enabled is True
+    assert layer.effects == []
+    assert layer.transform.scale_x == 1.0
+
+
+def test_layer_requires_source_for_media_types() -> None:
+    with pytest.raises(ValidationError, match="Quelle"):
+        Layer(name="Ohne Quelle", layer_type=LayerType.MEDIA)
+
+
+def test_adjustment_layer_rejects_source() -> None:
+    with pytest.raises(ValidationError, match="keine eigene Quelle"):
+        Layer(
+            name="Adj",
+            layer_type=LayerType.ADJUSTMENT,
+            source=_generator_source(),
+        )
+
+
+def test_max_two_effect_slots() -> None:
+    def fx(i: int) -> EffectInstance:
+        return EffectInstance(plugin_id="com.hms.fx.x", order_index=i)
+
+    with pytest.raises(ValidationError, match="zwei Effekt"):
+        _media_layer(effects=[fx(0), fx(1), fx(2)])
+
+
+def test_effect_order_index_unique() -> None:
+    fx = EffectInstance(plugin_id="com.hms.fx.x", order_index=0)
+    with pytest.raises(ValidationError, match="eindeutig"):
+        _media_layer(effects=[fx, fx.model_copy()])
+
+
+def test_opacity_bounds() -> None:
+    with pytest.raises(ValidationError):
+        _media_layer(opacity=1.5)
+
+
+# ---------- Composition (§10.1) ----------
+
+
+def test_composition_layer_ids_unique() -> None:
+    base = _media_layer()
+    duplicate = base.model_copy()
+    with pytest.raises(ValidationError, match="eindeutig"):
+        Composition(name="C", layers=[base, duplicate])
+
+
+def test_composition_max_64_layers() -> None:
+    layers = [
+        _media_layer(name=f"L{i}", source=_media_source()) for i in range(65)
+    ]
+    with pytest.raises(ValidationError, match="64"):
+        Composition(name="C", layers=layers)
+
+
+def test_composition_canvas_bounds() -> None:
+    comp = Composition(name="HD", width=1920, height=1080, fps=60.0)
+    assert comp.width == 1920
+    uhd = Composition(name="UHD", width=3840, height=2160)  # Desktop-Zielprofil (§3.3)
+    assert uhd.width == 3840
+    with pytest.raises(ValidationError):
+        Composition(name="Zu groß", width=9000)
+
+
+def test_layer_by_id_lookup() -> None:
+    layer = _media_layer()
+    comp = Composition(name="C", layers=[layer])
+    assert comp.layer_by_id(layer.id) is layer
+    assert comp.layer_by_id("unbekannt") is None
+
+
+# ---------- MediaAsset (§13.2, §9.1) ----------
+
+
+def test_media_asset_relative_path_required() -> None:
+    asset = MediaAsset(rel_path="clips/intro.mp4", container="mp4", video_codec="h264")
+    assert asset.content_hash is None  # optional bis Projektpaket (§13.2)
+    assert asset.seek_suitability == "unknown"  # ungeprüft, nie optimistisch
+
+
+def test_media_asset_rejects_absolute_path() -> None:
+    with pytest.raises(ValidationError, match="portabel-relativ"):
+        MediaAsset(rel_path="/absolut/clip.mp4")
+
+
+def test_media_asset_rejects_traversal() -> None:
+    with pytest.raises(ValidationError, match="portabel-relativ"):
+        MediaAsset(rel_path="../outside/clip.mp4")
+
+
+def test_project_rejects_duplicate_asset_paths() -> None:
+    a = MediaAsset(rel_path="clips/a.mp4")
+    b = MediaAsset(rel_path="clips/a.mp4")
+    with pytest.raises(ValidationError, match="Pfade müssen eindeutig"):
+        Project(media_assets=[a, b])  # §13.3: Duplikate erkennen
+
+
+def test_project_rejects_duplicate_asset_ids() -> None:
+    a = MediaAsset(id="1", rel_path="clips/a.mp4")
+    b = MediaAsset(id="1", rel_path="clips/b.mp4")
+    with pytest.raises(ValidationError, match="MediaAsset-IDs"):
+        Project(media_assets=[a, b])
+
+
+# ---------- OutputSurface (§10.1, §22.2) ----------
+
+
+def test_output_surface_defaults_hold_last_frame() -> None:
+    out = OutputSurface(node_id="00000000-0000-0000-0000-000000000009")
+    assert out.fallback_policy == "hold_last_frame"  # §26.1
+    assert out.slice_w == 1.0 and out.slice_h == 1.0  # volle Canvas als Default
+
+
+def test_output_surface_slice_bounds() -> None:
+    with pytest.raises(ValidationError):
+        OutputSurface(
+            node_id="00000000-0000-0000-0000-000000000009", slice_w=1.5
+        )
+
+
+# ---------- PresetScene (§18.1, §18.3) ----------
+
+
+def test_preset_scene_snapshot_and_transition() -> None:
+    comp = Composition(name="Show", layers=[_media_layer()])
+    scene = PresetScene(
+        name="Look 1",
+        composition_snapshot=comp.model_dump(),
+        transition_type=TransitionType.CROSSFADE,
+        transition_duration_s=2.0,
+    )
+    assert scene.composition_snapshot["name"] == "Show"
+    assert scene.transition_type is TransitionType.CROSSFADE
+    with pytest.raises(ValidationError):
+        PresetScene(name="X", composition_snapshot={}, transition_duration_s=99.0)
+
+
+# ---------- Project (§10.1, §24.4) ----------
+
+
+def test_project_schema_version_and_roundtrip() -> None:
+    asset = MediaAsset(rel_path="clips/intro.mp4")
+    comp = Composition(name="Main", layers=[_media_layer()])
+    project = Project(name="Meine Show", media_assets=[asset], compositions=[comp])
+    assert project.schema_version == 1
+    data = project.model_dump()
+    restored = Project.model_validate(data)
+    assert restored == project  # Persistenz-Roundtrip (SQLite speichert JSON, §24.2)
+    restored_comp = restored.composition_by_id(comp.id)
+    restored_asset = restored.asset_by_id(asset.id)
+    assert restored_comp is not None and restored_comp.id == comp.id
+    assert restored_asset is not None and restored_asset.rel_path == asset.rel_path
+
+
+def test_project_updated_at_changes_on_mutation() -> None:
+    """Timestamps verwaltet der Control Core explizit, nicht das Modell."""
+    project = Project(name="P")
+    before = project.updated_at
+    project.name = "Neuer Name"
+    assert project.updated_at == before