Early and precise diagnosis of bladder cancer (BC) is crucial for improving patient prognosis. BC-derived extracellular vesicles (BC-EVs), which carry specific molecular information from their parent tumor cells, are directly released into the urine to serve as noninvasive liquid biopsy targets. However, the clinical utility of BC-EVs is largely hindered by their low urinary abundance and high interference from massive nontumor EVs. To overcome this barrier, we present an in vivo metabolic engineering strategy for BC-EVs with a tumor-targeting reactive oxygen species (ROS)-responsive micelle probe. These smart probes specifically accumulate in bladder tumors and release azide-choline in response to the oxidative microenvironment, covalently incorporating azide moieties into nascent BC-EV membranes. Upon secretion into urine, these chemically tagged EVs are selectively enriched for precise BC diagnosis via bioorthogonal click chemistry, thereby effectively eliminating background interference. Crucially, this platform is able to distinguish nonmuscle-invasive BC from muscle-invasive BC based on the profiled biomarkers. This metabolic programming strategy can be extended to other diseases by simply changing the targeting and recognition moieties.