smart contract engineers

Abstract: Decentralized agent economies increasingly build a single task from protocols that were designed and secured separately. This creates a simple problem: a workflow can look correct at each step and still produce the wrong outcome. For example, a correct escrow may release payment on an authorized approval that provides little evidence that the delivered work actually satisfied the task. We systematize this problem across the full lifecycle of an agent task. Our study organizes security and economic requirements into 17 property families over six stages, with receipt soundness and completeness assessed separately. We examine 12 systems and standards, five reusable mechanism families, and four classical baselines. We introduce guarantee closure, a task-relative criterion for determining whether guarantees established at one stage remain available and constrain the later decisions that depend on them. We apply the criterion to controlled and native workflows, covering 840 matched executions and an exhaustive 11,648-case check over a finite objective-task domain. Our results expose recurring failures between verification and settlement, where conforming work can remain unaccepted or valid evidence can be ignored. Public records and model judgments further distinguish recorded approval from evidence of task conformance, while economic analysis identifies the report, penalty, and shared-error assumptions behind these guarantees. These findings show where end-to-end guarantees fail and what must be repaired to preserve them across the workflow.

Abstract: Stateless UTXO-style execution validates transactions using local and referenced data, enabling parallel validation and predictable serialized-size/weight accounting. Multi-step workflows thread state across outputs, and a prepared next-step transaction may become stale if another valid spend confirms first. Explicit state threading therefore shifts consistency maintenance, off-chain tracking, and transaction rebuilding to the protocol boundary, increasing coordination cost and latency. Recursive invariants (RIs), our proposed transaction-level logic and toolchain, address this gap by expressing workflow rules as transaction-level predicates over a transaction's inputs and indexed successor positions referenced by the RI. An accepted transaction realizing such a successor position re-checks the predecessor's RI one step later, carrying the workflow rule forward without shared mutable application state or executable output logic. Thus, multi-step protocol rules preserve validation-time locality and admit explicit cost accounting, while cross-transaction guarantees arise from repeated one-step checking. Not all successor clauses are checkable at validation time, so our small statically typed domain-specific language (DSL) uses three-valued semantics (true, false, unknown) to defer future-dependent obligations until checkable. Co-designed with this DSL, our framework formalizes UTXO validation and ledger extension, identifies the validation-time-evaluable one-step fragment, and proves the deduction system sound w.r.t. the three-valued semantics. We give validation and ledger-extension algorithms for this model. We implement a prototype RI interpreter and benchmarking toolchain for six workloads. Six practice-motivated case studies exhibit roughly linear cumulative validation-cost proxy growth and illustrate staged workflow constraints without preconstructing each successor.