Paper 2026/1674 Original: eprint.iacr.org/2026/1674 ↗

MinMandate: Private Task-Scoped Payment Authorization for Adaptive Agent Workflows

Abstract

Autonomous agents are increasingly used to plan and execute paid workflows on behalf of users. Existing agentic-payment frameworks support this delegation through merchant-admission authorization credentials but require the user to specify merchants before execution. However, complex paid workflows often span multiple services and merchants, and agents may choose among them based on intermediate results. This creates two limitations: (1) requiring the user to choose each merchant in advance either limits the agent's adaptability or forces the user back into the loop; and (2) reusing a stable identifier across merchants lets observers link separate paid calls and infer the user's broader intent. To address these limitations, we introduce MinMandate, which grants adaptive merchant selection within user-approved task bounds and derives fresh per-call payment views without introducing a stable cross-merchant identifier. Extensive experiments on AgentDojo tasks demonstrate that, when 50% of merchants are unavailable, MinMandate improves task success by 32.7 percentage points on average across four tested planners compared with an AP2 baseline that preauthorizes one merchant per service class. Reintroducing a reusable public payment-layer handle in the Stable Handle ablation raises attacker task-recovery success by 27.4 percentage points on average, isolating the privacy cost of a stable join handle. The code is available at https://github.com/Zora-G/minmandate.