Proof-or-Stop: Don't Trust the Agent, Trust the Evidence -- Loop Engineering for Verifiable Evidence-Gated Lifecycle Control
Autonomous coding agents are increasingly capable of performing complex software tasks, but they often operate in a way where their own reports—such as "tests passed" or "code reviewed"—are treated as final lifecycle states. This paper introduces "Proof-or-Stop Lifecycle Control," a method designed to prevent autonomous systems from advancing work based on unverified claims. Instead of trusting an agent’s narrative, the system requires fresh, mechanically verifiable evidence bound to the specific state of the code. If the evidence is missing, stale, or tampered with, the system stops or repairs the process rather than moving forward.
The Agent-as-Claim Model
The core philosophy of this research is that an agent’s output should be treated as a "claim" rather than a definitive state. In traditional workflows, a green pipeline or a simple "LGTM" from a reviewer might be enough to merge code. However, these can be misleading if the evidence is stale or disconnected from the current version of the software. Proof-or-Stop shifts this by requiring that every lifecycle transition—such as moving from "tested" to "done"—be backed by an evidence gate. This gate verifies that the evidence is current, cryptographically bound to the specific source code, and produced by an authorized actor.
How Evidence Gating Works
The system uses "Loop Engineering" to manage the development process. When an agent proposes a transition, the system checks the evidence against a set of strict requirements. This includes verifying the "material hash" (the state of the source tree), the "head hash" (the specific commit), and the "receipt identity" (the command, arguments, and output of the task). By using these cryptographic bindings, the system ensures that the evidence provided actually corresponds to the code being evaluated. If the evidence fails these checks, the system does not simply ignore the error; it triggers a bounded loop to repair the issue, escalate the problem, or halt the process entirely.
Key Results and Performance
The researchers evaluated this method through a series of mechanism tests and a large-scale ablation study. In a test of 9,240 scenarios, the gated loop significantly reduced the amplification of "visible-pass/hidden-fail" errors—cases where an agent reported success despite underlying defects. Specifically, the gated loop reduced these failures from 31 out of 1,800 cases in a naive, compute-budgeted loop down to just 2 out of 1,800. Furthermore, the system was tested against 18 different classes of tampering, successfully rejecting all of them with zero false accepts.
Scope and Limitations
It is important to note that Proof-or-Stop is a control layer, not a new coding model or a proof of semantic program correctness. It does not guarantee that code is bug-free; rather, it ensures that the lifecycle only advances when the claims made by the agent are supported by admissible, verifiable evidence. The current evaluation is limited to one model family, a specific set of 24 ablation tasks, and a self-hosted corpus. While the results demonstrate that this method is an effective way to manage autonomous agent workflows, the researchers emphasize that strong cross-vendor verification remains a future goal, and the system is designed to be host-neutral and model-agnostic.
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