diff --git a/server/streaming.py b/server/streaming.py
new file mode 100644
index 0000000..43b4503
--- /dev/null
+++ b/server/streaming.py
@@ -0,0 +1,90 @@
+"""WebSocket broadcast manager for streaming horror to connected clients."""
+
+import json
+import random
+
+from fastapi import WebSocket
+
+
+class StreamManager:
+    """Manages WebSocket clients and broadcasts horror events."""
+
+    TRANSITIONS = ["crossfade", "dissolve", "glitch_cut", "melt_morph"]
+
+    def __init__(self):
+        self._clients: set[WebSocket] = set()
+
+    @property
+    def client_count(self) -> int:
+        return len(self._clients)
+
+    def add_client(self, ws: WebSocket) -> None:
+        self._clients.add(ws)
+
+    def remove_client(self, ws: WebSocket) -> None:
+        self._clients.discard(ws)
+
+    async def _broadcast(self, message: str) -> None:
+        """Send to all clients, remove dead ones."""
+        dead: list[WebSocket] = []
+        for ws in self._clients:
+            try:
+                await ws.send_text(message)
+            except Exception:
+                dead.append(ws)
+        for ws in dead:
+            self._clients.discard(ws)
+
+    async def broadcast_phase(self, intensity: float, params: dict) -> None:
+        """Push a phase update with current intensity and rendering params."""
+        msg = json.dumps({
+            "type": "phase",
+            "intensity": round(intensity, 2),
+            "params": params,
+        })
+        await self._broadcast(msg)
+
+    async def broadcast_asset(
+        self, url: str, severity: float, transition: str | None = None,
+    ) -> None:
+        """Push a new image asset reference."""
+        if transition is None:
+            transition = random.choice(self.TRANSITIONS)
+        msg = json.dumps({
+            "type": "asset",
+            "url": url,
+            "severity": round(severity, 2),
+            "transition": transition,
+        })
+        await self._broadcast(msg)
+
+    async def broadcast_whisper(
+        self, url: str, pan: float, volume: float, reverb: float,
+    ) -> None:
+        """Push a whisper audio clip reference."""
+        msg = json.dumps({
+            "type": "whisper",
+            "url": url,
+            "pan": round(pan, 2),
+            "volume": round(volume, 2),
+            "reverb": round(reverb, 2),
+        })
+        await self._broadcast(msg)
+
+    async def broadcast_address(self, audio_b64: str, text: str) -> None:
+        """Push a direct address audio clip (base64-encoded WAV)."""
+        msg = json.dumps({
+            "type": "address",
+            "audio": audio_b64,
+            "text": text,
+        })
+        await self._broadcast(msg)
+
+    async def broadcast_scare(self, effect: str, duration_ms: int) -> None:
+        """Push a scare event (face flash, white-out, inversion, etc.)."""
+        msg = json.dumps({
+            "type": "scare",
+            "effect": effect,
+            "duration_ms": duration_ms,
+        })
+        await self._broadcast(msg)
diff --git a/tests/test_streaming.py b/tests/test_streaming.py
new file mode 100644
index 0000000..ee66d0c
--- /dev/null
+++ b/tests/test_streaming.py
@@ -0,0 +1,99 @@
+import asyncio
+import json
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from server.streaming import StreamManager
+
+
+@pytest.fixture
+def manager():
+    return StreamManager()
+
+
+@pytest.fixture
+def mock_ws():
+    ws = AsyncMock()
+    ws.send_text = AsyncMock()
+    return ws
+
+
+class TestClientManagement:
+    def test_add_client(self, manager, mock_ws):
+        """Adding a client increases count."""
+        manager.add_client(mock_ws)
+        assert manager.client_count == 1
+
+    def test_remove_client(self, manager, mock_ws):
+        """Removing a client decreases count."""
+        manager.add_client(mock_ws)
+        manager.remove_client(mock_ws)
+        assert manager.client_count == 0
+
+    def test_remove_missing_client(self, manager, mock_ws):
+        """Removing a non-existent client doesn't error."""
+        manager.remove_client(mock_ws)
+        assert manager.client_count == 0
+
+
+class TestBroadcast:
+    @pytest.mark.asyncio
+    async def test_broadcast_phase(self, manager, mock_ws):
+        """Phase update is broadcast to all clients."""
+        manager.add_client(mock_ws)
+        await manager.broadcast_phase(
+            intensity=2.4,
+            params={"morph_speed": 0.35, "shader_severity": 0.6, "palette": "crimson_void"},
+        )
+        mock_ws.send_text.assert_called_once()
+        msg = json.loads(mock_ws.send_text.call_args[0][0])
+        assert msg["type"] == "phase"
+        assert msg["intensity"] == 2.4
+        assert msg["params"]["morph_speed"] == 0.35
+
+    @pytest.mark.asyncio
+    async def test_broadcast_asset(self, manager, mock_ws):
+        """Asset notification is broadcast."""
+        manager.add_client(mock_ws)
+        await manager.broadcast_asset(
+            url="/assets/img/abc.png",
+            severity=1.8,
+            transition="melt",
+        )
+        msg = json.loads(mock_ws.send_text.call_args[0][0])
+        assert msg["type"] == "asset"
+        assert msg["url"] == "/assets/img/abc.png"
+
+    @pytest.mark.asyncio
+    async def test_broadcast_whisper(self, manager, mock_ws):
+        """Whisper notification is broadcast."""
+        manager.add_client(mock_ws)
+        await manager.broadcast_whisper(
+            url="/assets/audio/w01.wav",
+            pan=-0.3,
+            volume=0.4,
+            reverb=0.7,
+        )
+        msg = json.loads(mock_ws.send_text.call_args[0][0])
+        assert msg["type"] == "whisper"
+
+    @pytest.mark.asyncio
+    async def test_broadcast_scare(self, manager, mock_ws):
+        """Scare event is broadcast."""
+        manager.add_client(mock_ws)
+        await manager.broadcast_scare(effect="face_flash", duration_ms=150)
+        msg = json.loads(mock_ws.send_text.call_args[0][0])
+        assert msg["type"] == "scare"
+        assert msg["effect"] == "face_flash"
+
+    @pytest.mark.asyncio
+    async def test_dead_client_cleanup(self, manager):
+        """Dead clients are removed on broadcast."""
+        dead_ws = AsyncMock()
+        dead_ws.send_text = AsyncMock(side_effect=Exception("connection closed"))
+        manager.add_client(dead_ws)
+        assert manager.client_count == 1
+
+        await manager.broadcast_phase(intensity=1.0, params={})
+        assert manager.client_count == 0