diff --git a/backend/app/main.py b/backend/app/main.py
new file mode 100644
index 0000000..5c15d69
--- /dev/null
+++ b/backend/app/main.py
@@ -0,0 +1,67 @@
+"""AI Worker Platform - FastAPI Application Entry Point."""
+import os
+from contextlib import asynccontextmanager
+from fastapi import FastAPI, Request
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import JSONResponse
+from app.config import settings
+from app.database import init_db
+from app.api.v1 import api_router
+from app.core.exceptions import AppException
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    """Initialize database on startup."""
+    init_db()
+    # Seed default tenant if not exists
+    from app.database import SessionLocal
+    from app.models.tenant import Tenant
+    db = SessionLocal()
+    try:
+        existing = db.query(Tenant).filter(Tenant.slug == "default").first()
+        if not existing:
+            tenant = Tenant(name="Default Tenant", slug="default")
+            db.add(tenant)
+            db.commit()
+            print("[Startup] Created default tenant")
+    finally:
+        db.close()
+    print(f"[Startup] {settings.APP_NAME} v{settings.APP_VERSION} ready")
+    yield
+
+
+app = FastAPI(
+    title=settings.APP_NAME,
+    version=settings.APP_VERSION,
+    description="AI Worker Project Management Platform - MVP",
+    lifespan=lifespan,
+)
+
+# CORS
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=settings.cors_origins_list,
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+
+# Exception handler
+@app.exception_handler(AppException)
+async def app_exception_handler(request: Request, exc: AppException):
+    return JSONResponse(
+        status_code=exc.status_code,
+        content={"detail": exc.detail},
+    )
+
+
+# Health check
+@app.get("/health")
+def health():
+    return {"status": "ok", "version": settings.APP_VERSION}
+
+
+# API routes
+app.include_router(api_router)