Digs into a murky, wide-open problem where the question itself is not yet clear — "the system is slow lately", "customers are complaining", "something is off with the numbers". Use this whenever the user describes a vague or systemic problem with no single failing case to point at, asks you to look into or dig into something, or when a first look at a bug reveals it is bigger than one bug. For a specific reproducible failure, use debugging; this skill is for when you cannot yet write the reproduction.
