diff --git a/src/backend/api/dependencies.py b/src/backend/api/dependencies.py
new file mode 100644
index 0000000..f412284
--- /dev/null
+++ b/src/backend/api/dependencies.py
@@ -0,0 +1,8 @@
+from fastapi import Header, HTTPException
+
+from src.backend.config import settings
+
+
+async def verify_api_key(x_api_key: str | None = Header(default=None)):
+    if x_api_key is None or x_api_key != settings.api_key:
+        raise HTTPException(status_code=403, detail="API key non valida")
diff --git a/src/backend/api/routes/health.py b/src/backend/api/routes/health.py
new file mode 100644
index 0000000..57b127b
--- /dev/null
+++ b/src/backend/api/routes/health.py
@@ -0,0 +1,11 @@
+from fastapi import APIRouter, Depends
+
+from src.backend.api.dependencies import verify_api_key
+from src.backend.models.api import ok
+
+router = APIRouter(dependencies=[Depends(verify_api_key)])
+
+
+@router.get("/health", summary="Health check", tags=["system"])
+async def health():
+    return ok({"status": "running"})
diff --git a/src/backend/main.py b/src/backend/main.py
new file mode 100644
index 0000000..8fc28af
--- /dev/null
+++ b/src/backend/main.py
@@ -0,0 +1,17 @@
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+
+from src.backend.api.routes.health import router as health_router
+from src.backend.db.database import init_db
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    await init_db()
+    yield
+
+
+app = FastAPI(title="OpusAgent", version="0.1.0", lifespan=lifespan)
+
+app.include_router(health_router, prefix="/api")
diff --git a/tests/test_api_topics.py b/tests/test_api_topics.py
new file mode 100644
index 0000000..2d4a87e
--- /dev/null
+++ b/tests/test_api_topics.py
@@ -0,0 +1,150 @@
+import pytest
+from httpx import AsyncClient, ASGITransport
+
+
+@pytest.fixture
+def app():
+    from src.backend.main import app
+    return app
+
+
+@pytest.fixture
+async def client(app):
+    transport = ASGITransport(app=app)
+    async with AsyncClient(
+        transport=transport,
+        base_url="http://test",
+        headers={"X-Api-Key": "test-key-12345"},
+    ) as ac:
+        yield ac
+
+
+@pytest.fixture
+async def client_no_auth(app):
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url="http://test") as ac:
+        yield ac
+
+
+@pytest.mark.asyncio
+async def test_request_without_api_key_returns_403(client_no_auth):
+    resp = await client_no_auth.get("/api/health")
+    assert resp.status_code == 403
+
+
+@pytest.mark.asyncio
+async def test_request_with_wrong_api_key_returns_403(app):
+    transport = ASGITransport(app=app)
+    async with AsyncClient(
+        transport=transport,
+        base_url="http://test",
+        headers={"X-Api-Key": "wrong-key"},
+    ) as ac:
+        resp = await ac.get("/api/health")
+        assert resp.status_code == 403
+
+
+@pytest.mark.asyncio
+async def test_create_topic(client):
+    resp = await client.post(
+        "/api/topics",
+        json={
+            "name": "coding",
+            "system_prompt": "You are an expert coder.",
+            "summary": "Coding topic",
+            "model": "claude-sonnet-4-6",
+        },
+    )
+    assert resp.status_code == 201
+    data = resp.json()
+    assert data["success"] is True
+    assert data["data"]["name"] == "coding"
+    assert data["data"]["model"] == "claude-sonnet-4-6"
+    assert "id" in data["data"]
+
+
+@pytest.mark.asyncio
+async def test_create_topic_minimal(client):
+    resp = await client.post(
+        "/api/topics",
+        json={"name": "analysis", "system_prompt": "You analyze data."},
+    )
+    assert resp.status_code == 201
+    data = resp.json()
+    assert data["data"]["summary"] == ""
+    assert data["data"]["model"] is None
+
+
+@pytest.mark.asyncio
+async def test_create_topic_duplicate_name_fails(client):
+    await client.post(
+        "/api/topics",
+        json={"name": "coding", "system_prompt": "Prompt 1"},
+    )
+    resp = await client.post(
+        "/api/topics",
+        json={"name": "coding", "system_prompt": "Prompt 2"},
+    )
+    assert resp.status_code == 409
+
+
+@pytest.mark.asyncio
+async def test_list_topics(client):
+    await client.post(
+        "/api/topics", json={"name": "a", "system_prompt": "A"}
+    )
+    await client.post(
+        "/api/topics", json={"name": "b", "system_prompt": "B"}
+    )
+    resp = await client.get("/api/topics")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert len(data["data"]) == 2
+
+
+@pytest.mark.asyncio
+async def test_get_topic(client):
+    create_resp = await client.post(
+        "/api/topics", json={"name": "coding", "system_prompt": "Code"}
+    )
+    topic_id = create_resp.json()["data"]["id"]
+
+    resp = await client.get(f"/api/topics/{topic_id}")
+    assert resp.status_code == 200
+    assert resp.json()["data"]["name"] == "coding"
+
+
+@pytest.mark.asyncio
+async def test_get_topic_not_found(client):
+    resp = await client.get("/api/topics/nonexistent-id")
+    assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_update_topic(client):
+    create_resp = await client.post(
+        "/api/topics", json={"name": "coding", "system_prompt": "Old"}
+    )
+    topic_id = create_resp.json()["data"]["id"]
+
+    resp = await client.put(
+        f"/api/topics/{topic_id}",
+        json={"system_prompt": "New prompt"},
+    )
+    assert resp.status_code == 200
+    assert resp.json()["data"]["system_prompt"] == "New prompt"
+    assert resp.json()["data"]["name"] == "coding"
+
+
+@pytest.mark.asyncio
+async def test_delete_topic(client):
+    create_resp = await client.post(
+        "/api/topics", json={"name": "coding", "system_prompt": "Code"}
+    )
+    topic_id = create_resp.json()["data"]["id"]
+
+    resp = await client.delete(f"/api/topics/{topic_id}")
+    assert resp.status_code == 200
+
+    resp = await client.get(f"/api/topics/{topic_id}")
+    assert resp.status_code == 404