Counterspy

You create an intricate arcane circle made of candles and
sand centered on a point on the ground within range. The
circle can have a radius of 10 feet or less. If at any point
before the spell ends a creature outside the circle can see
or hear you through magical or nonmagical means, the
candle’s flames will change color. If a spell or magical effect
was used, you are aware of it and understand the extent of
its effects.