Abstract: Stablecoin transfers are often interpreted as payments. On pro grammable blockchains, however, they are frequently embedded in atomically executed transaction bundles that combine trading, lending, arbitrage, liquid ity provision, and settlement. We show that ignoring this structure materi ally distorts the interpretation of stablecoin activity. Using 593 million event logs from 141 million Ethereum transactions involving three major U.S. dollar stablecoins, we develop a replicable framework to measure transaction com plexity from archive node data, public contract labels, and event signatures. The analysis combines measures of token and contract co-usage, action type, computational complexity, urgency, and timing. Two results emerge. First, complexity is a first-order feature of stablecoin activity: nearly 60 percent of transfer events occur within complex transactions. Second, the three stable coins are not used interchangeably: their use differs systematically across trans action structures, urgency, and timing, consistent with distinct institutional designs and economic functions. Analyses that treat transfers as standalone payments therefore risk misclassifying a large share of on-chain stablecoin use, with implications for empirical measurement, market monitoring, and policy

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