Update app.py

app.py

@@ -13,6 +13,9 @@ from quread.circuit_diagram import draw_circuit_svg
 from quread.cost_guard import allow_request
 from quread.export_pdf import md_to_pdf
 
+# --- Qubit cap (configurable) ---
+DEFAULT_MAX_QUBITS = 16  # safe default for CPU Spaces; change if you want
+MAX_QUBITS = int(os.getenv("QUREAD_MAX_QUBITS", DEFAULT_MAX_QUBITS))
 
 # ---------- Helpers ----------
 def _new_sim(n_qubits: int):
@@ -173,7 +176,8 @@ with gr.Blocks(theme=theme, css=CSS, title="Quread.ai — State Vector Studio")
         # Sidebar
         with gr.Column(scale=3, elem_classes=["sidebar"]):
             gr.Markdown("### Simulator Settings")
-            n_qubits = gr.Slider(1, 10, value=2, step=1, label="Number of qubits")
+            n_qubits = gr.Slider(1, MAX_QUBITS, value=2, step=1, label="Number of qubits")
+            gr.Markdown(f"<div class='small-note'>Max qubits: <b>{MAX_QUBITS}</b> (set env var <code>QUREAD_MAX_QUBITS</code> to change)</div>")
             shots = gr.Slider(128, 8192, value=1024, step=128, label="Shots")
 
             gr.Markdown("---")