diff --git a/src/alpine_bits_python/api.py b/src/alpine_bits_python/api.py
index 1047e56..faf140c 100644
--- a/src/alpine_bits_python/api.py
+++ b/src/alpine_bits_python/api.py
@@ -57,6 +57,9 @@ security_basic = HTTPBasic()
 # HTTP Bearer auth for API endpoints
 security_bearer = HTTPBearer()
 
+# Constants for token sanitization
+TOKEN_LOG_LENGTH = 10
+
 
 # Pydantic models for language detection
 class LanguageDetectionRequest(BaseModel):
@@ -405,9 +408,25 @@ async def detect_language(
     token = credentials.credentials
     config = request.app.state.config
 
-    # Check if token is valid (you may want to implement proper token validation)
+    # Check if token is valid
     valid_tokens = config.get("api_tokens", [])
-    if not valid_tokens or token not in valid_tokens:
+
+    # If no tokens configured, reject authentication
+    if not valid_tokens:
+        _LOGGER.error("No api_tokens configured in config.yaml")
+        raise HTTPException(
+            status_code=401,
+            detail="Authentication token not configured on server",
+        )
+
+    if token not in valid_tokens:
+        # Log sanitized token (first TOKEN_LOG_LENGTH chars) for security
+        sanitized_token = (
+            token[:TOKEN_LOG_LENGTH] + "..."
+            if len(token) > TOKEN_LOG_LENGTH
+            else token
+        )
+        _LOGGER.warning("Invalid token attempt: %s", sanitized_token)
         raise HTTPException(
             status_code=401,
             detail="Invalid authentication token",