Bacteriophages are potent therapeutics against biohazardous bacteria that are rapidly acquiring multidrug resistance. However, routine administration of bacteriophage therapy is currently impeded by a lack of safe phage production methodologies and insufficient phage characterization. We thus developed a versatile cell-free platform for host-independent production of phages targeting gram-positive and gram-negative bacteria. A few microliters of a one-pot reaction produces effective doses of phages against potentially antibiotic-resistant bacteria such as enterohemorrhagic E. coli (EAEC) and Yersinia pestis, which also possibly pose threats as biological warfare agents. We also introduce a method for transient, non-genomic phage engineering to safely confer additional functions, such as a purification tag or bioluminescence for host detection, for only one replication cycle. Using high-resolution and time-resolved mass spectrometry, we validated the expression of 40 hypothetical proteins from two different phages (T7 and CLB-P3) and identified genes in the genome of phage T7 that express exceptionally late during phage replication. Our comprehensive methodology thus allows for accelerated reverse and forward phage engineering as well as for safe and customized production of clinical-grade therapeutic bacteriophages.