  Quantum coherence, nonlocality, and contextuality are key resources for
quantum advantage in metrology, communication, and computation. We introduce a
graph-based approach to derive classicality inequalities that bound local,
non-contextual, and coherence-free models, offering a unified description of
these seemingly disparate quantum resources. Our approach generalizes recently
proposed basis-independent coherence witnesses, and recovers all
non-contextuality inequalities of the exclusivity graph approach. Moreover,
violations of certain classicality inequalities witness preparation
contextuality. We describe an algorithm to find all such classicality
inequalities, and use it to analyze some of the simplest scenarios.
