Update app.py

app.py

@@ -54,7 +54,7 @@ def ensure_sno(df):
 
 
 # -----------------------------
-# Upload (NO session_state)
+# Upload (fully defensive)
 # -----------------------------
 uploaded = st.file_uploader("Upload Excel (.xlsx)", type=["xlsx"])
 
@@ -62,10 +62,21 @@ if uploaded is None:
     st.info("Upload an Excel file to begin.")
     st.stop()
 
-# Read bytes safely
-file_bytes = uploaded.getvalue()
+# User action gate (prevents HF startup/bare-mode crash)
+load = st.button("✅ Load file")
+if not load:
+    st.warning("After uploading, click **Load file**.")
+    st.stop()
+
+# Read bytes safely (prefer read() on HF)
+try:
+    file_bytes = uploaded.read()
+except Exception as e:
+    st.error(f"Failed to read uploaded file: {e}")
+    st.stop()
+
 if not file_bytes:
-    st.warning("Uploaded file is empty. Please re-upload.")
+    st.error("Uploaded file is empty. Please re-upload.")
     st.stop()
 
 # Force openpyxl
@@ -87,6 +98,9 @@ except Exception as e:
 
 raw = normalize_headers(raw)
 
+# -----------------------------
+# Build dataframe
+# -----------------------------
 grade_col = pick_grade_column(raw)
 df = raw.copy()
 df, sno_col = ensure_sno(df)