diff --git a/meeting_room/server.py b/meeting_room/server.py
index 210cfef..047f366 100644
--- a/meeting_room/server.py
+++ b/meeting_room/server.py
@@ -3,7 +3,9 @@
 from __future__ import annotations
 
 import asyncio
+import json
 import logging
+import os
 import uuid
 from contextlib import asynccontextmanager
 from typing import Any
@@ -16,7 +18,7 @@ from pydantic import BaseModel
 from meeting_room.api_client import APIClient
 from meeting_room.config import load_config, load_discussion_config, find_workspace_config
 from meeting_room.engine import DiscussionEngine
-from meeting_room.events import AsyncEventBridge, EventEmitter
+from meeting_room.events import AGENT_ERROR, AGENT_MESSAGE, BOSS_TURN, AsyncEventBridge, EventEmitter
 from meeting_room.models import DiscussionConfig, ProviderConfig
 from meeting_room.scenario_loader import load_scenario
 from meeting_room.tools import ToolRegistry
@@ -60,11 +62,11 @@ class SessionDetailResponse(BaseModel):
 
 
 # ---------------------------------------------------------------------------
-# Session store
+# Session state (renamed from Session to avoid collision with models.Session)
 # ---------------------------------------------------------------------------
 
 
-class Session:
+class ServerSession:
     """Holds state for a single discussion session."""
 
     def __init__(
@@ -82,8 +84,10 @@ class Session:
         self.event_bus = EventEmitter()
         self.bridge = AsyncEventBridge(self.event_bus)
         self._engine_task: asyncio.Task | None = None
+        self._collect_handler = None  # stored for cleanup
 
     def build_engine(self) -> DiscussionEngine:
+        """Build a DiscussionEngine using this session's event_bus."""
         providers = {
             name: ProviderConfig(**vals)
             for name, vals in self.config.get("providers", {}).items()
@@ -97,23 +101,31 @@ class Session:
             events=self.event_bus,
         )
 
+    def cleanup(self) -> None:
+        """Stop bridge and remove event handlers."""
+        self.bridge.stop()
+        if self._collect_handler is not None:
+            for event_type in (AGENT_MESSAGE, BOSS_TURN, AGENT_ERROR):
+                self.event_bus.off(event_type, self._collect_handler)
+            self._collect_handler = None
+
 
 class SessionStore:
     """In-memory session store."""
 
     def __init__(self) -> None:
-        self._sessions: dict[str, Session] = {}
+        self._sessions: dict[str, ServerSession] = {}
 
-    def create(self, config: dict, discussion_config: DiscussionConfig) -> Session:
+    def create(self, config: dict, discussion_config: DiscussionConfig) -> ServerSession:
         session_id = uuid.uuid4().hex[:12]
-        session = Session(session_id, config, discussion_config)
+        session = ServerSession(session_id, config, discussion_config)
         self._sessions[session_id] = session
         return session
 
-    def get(self, session_id: str) -> Session | None:
+    def get(self, session_id: str) -> ServerSession | None:
         return self._sessions.get(session_id)
 
-    def list_sessions(self) -> list[Session]:
+    def list_sessions(self) -> list[ServerSession]:
         return list(self._sessions.values())
 
 
@@ -129,22 +141,22 @@ async def lifespan(app: FastAPI):
     """Startup/shutdown lifecycle."""
     logger.info("Meeting Room server started")
     yield
-    # Cleanup: cancel any running engine tasks
+    # Cleanup: cancel running engine tasks and stop bridges
     for session in store.list_sessions():
         if session._engine_task and not session._engine_task.done():
             session._engine_task.cancel()
+        session.cleanup()
     logger.info("Meeting Room server stopped")
 
 
 app = FastAPI(
     title="Meeting Room",
-    version="0.2.0",
+    version="0.2.1",
     description="Multi-agent discussion framework — REST API and WebSocket",
     lifespan=lifespan,
 )
 
 # Serve static files (web UI)
-import os
 _static_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "static")
 app.mount("/static", StaticFiles(directory=_static_dir), name="static")
 
@@ -152,7 +164,6 @@ app.mount("/static", StaticFiles(directory=_static_dir), name="static")
 @app.get("/")
 async def index():
     """Redirect to the web UI."""
-    from fastapi.responses import RedirectResponse
     return RedirectResponse(url="/static/index.html")
 
 
@@ -171,6 +182,44 @@ def _load_config_or_default(config_path: str | None) -> dict:
     return load_config()
 
 
+def _resolve_scenario_path(scenario: str) -> str:
+    """Resolve scenario path, preventing path traversal.
+
+    Only allows scenarios from CWD or the package scenarios directory.
+    """
+    # Reject path traversal
+    if ".." in scenario:
+        raise HTTPException(status_code=400, detail="Invalid scenario path: path traversal not allowed")
+
+    if os.path.isabs(scenario_path := scenario):
+        if not os.path.exists(scenario_path):
+            raise HTTPException(status_code=404, detail=f"Scenario not found: {scenario}")
+        return scenario_path
+
+    # Try relative to CWD first
+    cwd_path = os.path.join(os.getcwd(), scenario)
+    if os.path.exists(cwd_path):
+        return cwd_path
+
+    # Try package scenarios directory
+    pkg_path = os.path.join(os.path.dirname(os.path.abspath(__file__)), "scenarios", scenario)
+    if os.path.exists(pkg_path):
+        return pkg_path
+
+    raise HTTPException(status_code=404, detail=f"Scenario not found: {scenario}")
+
+
+def _mask_api_keys(providers: dict) -> dict:
+    """Mask API keys in provider config for safe display."""
+    masked = {}
+    for name, cfg in providers.items():
+        masked[name] = {
+            "base_url": cfg.get("base_url", ""),
+            "api_key": cfg.get("api_key", "")[:4] + "****" if cfg.get("api_key") else "",
+        }
+    return masked
+
+
 # ---------------------------------------------------------------------------
 # REST API (mounted at /api)
 # ---------------------------------------------------------------------------
@@ -225,18 +274,8 @@ async def start_discussion(session_id: str, body: StartDiscussionRequest):
     if session.status == "running":
         raise HTTPException(status_code=409, detail="Discussion already running")
 
-    # Load scenario
-    import os
-    scenario_path = body.scenario
-    if not os.path.isabs(scenario_path):
-        scenario_path = os.path.join(os.getcwd(), scenario_path)
-    if not os.path.exists(scenario_path):
-        scenario_path = os.path.join(
-            os.path.dirname(os.path.abspath(__file__)), "scenarios", body.scenario
-        )
-    if not os.path.exists(scenario_path):
-        raise HTTPException(status_code=404, detail=f"Scenario not found: {body.scenario}")
-
+    # Resolve and validate scenario path
+    scenario_path = _resolve_scenario_path(body.scenario)
     scenario_data = load_scenario(scenario_path)
     session.scenario_name = scenario_data.get("name", "Untitled")
 
@@ -247,13 +286,11 @@ async def start_discussion(session_id: str, body: StartDiscussionRequest):
         session.config = raw_config
         session.discussion_config = discussion_config
 
-    # Start the bridge
-    loop = asyncio.get_event_loop()
+    # Start the bridge on the running event loop
+    loop = asyncio.get_running_loop()
     session.bridge.start(loop)
 
-    # Subscribe a handler to collect messages
-    from meeting_room.events import AGENT_MESSAGE, BOSS_TURN, AGENT_ERROR
-
+    # Subscribe a handler to collect messages (stored for cleanup)
     def collect_message(event):
         session.messages.append({
             "role_id": event.data.get("role_id", ""),
@@ -261,6 +298,7 @@ async def start_discussion(session_id: str, body: StartDiscussionRequest):
             "content": event.data.get("content", event.data.get("error", "")),
         })
 
+    session._collect_handler = collect_message
     session.event_bus.on(AGENT_MESSAGE, collect_message)
     session.event_bus.on(BOSS_TURN, collect_message)
     session.event_bus.on(AGENT_ERROR, collect_message)
@@ -277,7 +315,7 @@ async def start_discussion(session_id: str, body: StartDiscussionRequest):
             logger.exception("Engine error in session %s", session.id)
             session.status = "error"
         finally:
-            session.bridge.stop()
+            session.cleanup()
 
     session._engine_task = asyncio.create_task(run_engine())
 
@@ -291,20 +329,20 @@ async def start_discussion(session_id: str, body: StartDiscussionRequest):
 
 @api.post("/sessions/{session_id}/inject", response_model=dict)
 async def inject_message(session_id: str, body: InjectMessageRequest):
-    """Inject a message from a Boss/CSO role."""
+    """Inject a message from a Boss/CSO role.
+
+    Uses the session's event_bus so WebSocket/SSE clients receive the event.
+    """
     session = store.get(session_id)
     if not session:
         raise HTTPException(status_code=404, detail="Session not found")
     if session.status != "running":
         raise HTTPException(status_code=409, detail="Session is not running")
 
+    # Use the session's event_bus — inject_message emits BOSS_TURN on it,
+    # which the bridge forwards to all subscribers (WebSocket/SSE).
     engine = session.build_engine()
     msg = engine.inject_message(body.role_id, body.content)
-    session.messages.append({
-        "role_id": msg.role_id,
-        "name": msg.name,
-        "content": msg.content,
-    })
 
     return {"role_id": msg.role_id, "name": msg.name, "content": msg.content}
 
@@ -327,9 +365,9 @@ async def list_roles(config: str | None = None):
 
 @api.get("/providers")
 async def list_providers(config: str | None = None):
-    """List configured providers."""
+    """List configured providers (API keys masked)."""
     raw_config = _load_config_or_default(config)
-    return raw_config.get("providers", {})
+    return _mask_api_keys(raw_config.get("providers", {}))
 
 
 # Mount API router
@@ -351,42 +389,34 @@ async def websocket_endpoint(websocket: WebSocket, session_id: str):
 
     await websocket.accept()
     queue = session.bridge.subscribe()
+    send_task = asyncio.create_task(_ws_send_loop(websocket, queue))
 
     try:
-        # Task: forward events from queue to WebSocket
-        async def send_events():
-            try:
-                while True:
-                    event = await queue.get()
-                    await websocket.send_json(event)
-            except asyncio.CancelledError:
-                pass
-
-        send_task = asyncio.create_task(send_events())
-
-        # Listen for incoming messages (inject)
-        try:
-            while True:
-                data = await websocket.receive_json()
-                if data.get("type") == "inject":
-                    role_id = data.get("role_id", "boss")
-                    content = data.get("content", "")
-                    engine = session.build_engine()
-                    msg = engine.inject_message(role_id, content)
-                    session.messages.append({
-                        "role_id": msg.role_id,
-                        "name": msg.name,
-                        "content": msg.content,
-                    })
-        except WebSocketDisconnect:
-            pass
-        finally:
-            send_task.cancel()
-            session.bridge.unsubscribe(queue)
-    except Exception:
+        while True:
+            data = await websocket.receive_json()
+            if data.get("type") == "inject":
+                role_id = data.get("role_id", "boss")
+                content = data.get("content", "")
+                # Use session's event_bus so events reach all subscribers
+                engine = session.build_engine()
+                engine.inject_message(role_id, content)
+    except WebSocketDisconnect:
+        pass
+    finally:
+        send_task.cancel()
         session.bridge.unsubscribe(queue)
 
 
+async def _ws_send_loop(websocket: WebSocket, queue: asyncio.Queue[dict]) -> None:
+    """Forward events from bridge queue to WebSocket."""
+    try:
+        while True:
+            event = await queue.get()
+            await websocket.send_json(event)
+    except asyncio.CancelledError:
+        pass
+
+
 # ---------------------------------------------------------------------------
 # SSE
 # ---------------------------------------------------------------------------
@@ -404,8 +434,6 @@ async def sse_endpoint(session_id: str):
         try:
             while True:
                 event = await queue.get()
-                # SSE format
-                import json
                 yield f"data: {json.dumps(event)}\n\n"
         except asyncio.CancelledError:
             pass
diff --git a/meeting_room/static/index.html b/meeting_room/static/index.html
index bc82388..c0cb2aa 100644
--- a/meeting_room/static/index.html
+++ b/meeting_room/static/index.html
@@ -255,12 +255,12 @@
                 const el = document.createElement('div');
                 el.className = 'msg';
                 const color = ROLE_COLORS[d.role_id] || '#999';
-                el.innerHTML = `<div class="name" style="color:${color}">${d.name}</div><div class="content">${escapeHtml(d.content || '')}</div>`;
+                el.innerHTML = `<div class="name" style="color:${color}">${escapeHtml(d.name)}</div><div class="content">${escapeHtml(d.content || '')}</div>`;
                 container.appendChild(el);
             } else if (type === 'agent_error') {
                 const el = document.createElement('div');
                 el.className = 'msg error';
-                el.innerHTML = `<div class="name">${d.name}</div><div class="content">Error: ${escapeHtml(d.error || '')}</div>`;
+                el.innerHTML = `<div class="name">${escapeHtml(d.name)}</div><div class="content">Error: ${escapeHtml(d.error || '')}</div>`;
                 container.appendChild(el);
             } else if (type === 'tool_call') {
                 const el = document.createElement('div');
diff --git a/tests/test_server.py b/tests/test_server.py
index 83b5f0e..b4acdf6 100644
--- a/tests/test_server.py
+++ b/tests/test_server.py
@@ -5,10 +5,11 @@ from __future__ import annotations
 import asyncio
 
 import pytest
+from fastapi import HTTPException
 from fastapi.testclient import TestClient
 
 from meeting_room.events import AsyncEventBridge, EventEmitter
-from meeting_room.server import Session, SessionStore, app, store
+from meeting_room.server import ServerSession, SessionStore, app, store
 
 
 @pytest.fixture(autouse=True)
@@ -113,13 +114,53 @@ class TestRolesAndProviders:
 # ---------------------------------------------------------------------------
 
 
-class TestSession:
+class TestServerSession:
     def test_build_engine(self) -> None:
         config = _minimal_config()
-        session = Session("test-id", config, _minimal_discussion_config())
+        session = ServerSession("test-id", config, _minimal_discussion_config())
         engine = session.build_engine()
         assert engine is not None
 
+    def test_cleanup_removes_collect_handler(self) -> None:
+        from meeting_room.events import AGENT_MESSAGE, BOSS_TURN, AGENT_ERROR
+        config = _minimal_config()
+        session = ServerSession("test-id", config, _minimal_discussion_config())
+        # Simulate what start_discussion does
+        def collect_message(event):
+            pass
+        session._collect_handler = collect_message
+        session.event_bus.on(AGENT_MESSAGE, collect_message)
+        session.event_bus.on(BOSS_TURN, collect_message)
+        session.event_bus.on(AGENT_ERROR, collect_message)
+        assert len(session.event_bus.handlers(AGENT_MESSAGE)) == 1
+        session.cleanup()
+        assert len(session.event_bus.handlers(AGENT_MESSAGE)) == 0
+
+
+class TestProviderMasking:
+    def test_api_keys_masked(self) -> None:
+        from meeting_room.server import _mask_api_keys
+        providers = {
+            "routerai": {"base_url": "https://api.example.com", "api_key": "sk-1234567890abcdef"},
+        }
+        masked = _mask_api_keys(providers)
+        assert masked["routerai"]["api_key"] == "sk-1****"
+        assert masked["routerai"]["base_url"] == "https://api.example.com"
+
+    def test_empty_key(self) -> None:
+        from meeting_room.server import _mask_api_keys
+        providers = {"test": {"base_url": "https://x.com", "api_key": ""}}
+        masked = _mask_api_keys(providers)
+        assert masked["test"]["api_key"] == ""
+
+
+class TestPathTraversal:
+    def test_reject_parent_dir(self) -> None:
+        from meeting_room.server import _resolve_scenario_path
+        with pytest.raises(HTTPException) as exc_info:
+            _resolve_scenario_path("../../etc/passwd")
+        assert exc_info.value.status_code == 400
+
 
 # ---------------------------------------------------------------------------
 # Helper