Update app.py

app.py

@@ -105,8 +105,11 @@ def train_and_save(df: pd.DataFrame):
 
     # Categorical columns
     for c in CAT_COLS:
+    # Convert everything to string consistently; keep missing as np.nan
         X[c] = X[c].astype("object")
         X.loc[X[c].isna(), c] = np.nan
+        X[c] = X[c].map(lambda v: v if pd.isna(v) else str(v))
+
 
     y01, pos_class = coerce_binary_label(y_raw)
 
@@ -230,7 +233,11 @@ with tab_predict:
             X_inf = df_inf[FEATURE_COLS].copy()
             X_inf = X_inf.replace({pd.NA: np.nan})
 
-
+            for c in CAT_COLS:
+                X_inf[c] = X_inf[c].astype("object")
+                X_inf.loc[X_inf[c].isna(), c] = np.nan
+                X_inf[c] = X_inf[c].map(lambda v: v if pd.isna(v) else str(v))
+ 
             for c in NUM_COLS:
                 X_inf[c] = pd.to_numeric(X_inf[c], errors="coerce")
             for c in CAT_COLS: