diff --git a/.gitignore b/.gitignore
index 4172497..4f273e9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,5 @@
 __pycache__/
 *.pyc
 activation.log
+
+data/devices/*.json
diff --git a/app.py b/app.py
index 7cc25b2..9e481de 100644
--- a/app.py
+++ b/app.py
@@ -15,6 +15,7 @@ app = FastAPI(title="Provisioning Activation Server", version="0.1.0")
 
 class ActivationRequest(BaseModel):
     activation_code: str
+    device_fingerprint: str
     hostname: str | None = None
     machine_id: str | None = None
     client_version: str | None = None
@@ -29,6 +30,43 @@ def write_log(entry: dict) -> None:
     with LOG_PATH.open("a", encoding="utf-8") as f:
         f.write(json.dumps(entry, ensure_ascii=False) + "\n")
 
+DEVICES_DIR = Path("data/devices")
+
+def load_or_create_device(device_fingerprint: str) -> tuple[dict, bool]:
+    """
+    Lädt ein bekanntes Gerät oder legt es neu an.
+
+    Rückgabe:
+        (device, created)
+    """
+
+    DEVICES_DIR.mkdir(parents=True, exist_ok=True)
+
+    device_file = DEVICES_DIR / f"{device_fingerprint}.json"
+
+    if device_file.exists():
+        with device_file.open("r", encoding="utf-8") as f:
+            device = json.load(f)
+
+        device["last_seen"] = datetime.now(timezone.utc).isoformat()
+        device["activation_count"] = device.get("activation_count", 0) + 1
+
+        with device_file.open("w", encoding="utf-8") as f:
+            json.dump(device, f, indent=2)
+
+        return device, False
+
+    device = {
+        "device_fingerprint": device_fingerprint,
+        "created_at": datetime.now(timezone.utc).isoformat(),
+        "last_seen": datetime.now(timezone.utc).isoformat(),
+        "activation_count": 1
+    }
+
+    with device_file.open("w", encoding="utf-8") as f:
+        json.dump(device, f, indent=2)
+
+    return device, True
 
 @app.get("/health")
 def health():
@@ -45,6 +83,13 @@ def activate(payload: ActivationRequest, request: Request):
     activation_entry = config.get("activation_codes", {}).get(payload.activation_code)
 
     success = activation_entry is not None
+    device = None
+    device_created = False
+
+    if success:
+        device, device_created = load_or_create_device(
+            payload.device_fingerprint
+        )
 
     write_log({
         "timestamp": datetime.now(timezone.utc).isoformat(),
@@ -73,6 +118,11 @@ def activate(payload: ActivationRequest, request: Request):
 
     return {
         "success": True,
+
+        "device": {
+        "fingerprint": device["device_fingerprint"],
+        },
+
         "customer": activation_entry["customer"],
         "profiles": available_profiles
     }
diff --git a/data/devices/.gitkeep b/data/devices/.gitkeep
new file mode 100644
index 0000000..e69de29