Introduction Diazepam enters aquatic environments via wastewater and illegal use in live fish transport, yet its hepatic toxicity mechanisms in crucian carp ( Carassius auratus )—a key species linking freshwater and estuarine food webs—remain unclear. This study established a multi‑level toxicity framework to clarify diazepam‑induced hepatotoxicity and ecological risks. Methods Acute toxicity tests determined 96‑h LC 50 and sa...