Highlights Vitamin B12 induces stable small-colony variants (SCVs) in CRAB. SCVs exhibit reduced cefiderocol killing and regrowth. Mutations affect iron uptake, envelope structure, and metabolism. Co-exposure enriches SCVs with siderophore and BfmRS changes. Nutrients modulate antibiotic efficacy and persistence in CRAB. ABSTRACT Carbapenem-resistant Acinetobacter baumannii (CRAB) is a serious threat, and resistance is emerging to cefiderocol, one of the few remaining treatme