PlanFence: Dependency-Scoped Validation Against Stale-Plan Execution in Distributed LLM-Agent Memory

Forum topic · 小凯 · 2026-09-06

Summary

Distributed LLM-agent teams can read the latest shared facts yet still execute actions based on obsolete plans—a failure mode the authors call stale-plan execution: state freshness does not guarantee that the plan authorizing an action remains valid. This paper introduces PlanFence, a dependency-scoped action-validation protocol in which plans cite the exact public records they used, and executors validate only records that could affect the pending external action, replanning once or blocking when validation is incomplete. In 30 controlled live workflows containing post-plan revisions, a freshness-only executor acted on an obsolete plan in every task, whereas PlanFence completed all tasks without invalid actions. Controlled replays reveal two conditional boundaries: proactive synchronization yields lower coordination stalls at low churn rates, while PlanFence avoids repeated update-path coordination as churn grows and avoids validating irrelevant state as the shared key space grows. The results are controlled safety and system-cost findings rather than general task-accuracy improvements. Paper: arXiv:2509.00004.

Paper Overview

Field: AI/ML Authors: Evan Chen, Shiqiang Wang, Christopher G. Brinton Published: 2026-09-06 arXiv: 2509.00004

Key Idea

Distributed LLM-agent teams can read the latest shared facts and still act on an obsolete plan. A planner may derive an action from requirement r₃, another agent may commit r₄, and an executor may receive r₄ without replacing the plan derived from r₃. The authors call this stale-plan execution: state freshness does not establish that the plan authorizing an action remains valid.

PlanFence Protocol

Plans cite the exact public records they used.
Executors validate only the records that can affect the pending external action (dependency-scoped validation).
When validation is incomplete, the executor replans once or blocks.

Experimental Findings

In 30 controlled live workflows with a post-plan revision, a freshness-only executor acted on the obsolete plan in every task, whereas PlanFence completed all tasks with no invalid actions.
Controlled replays reveal two conditional boundaries:
Proactive synchronization yields lower coordination stalls at low churn rates.
PlanFence avoids repeated update-path coordination as churn grows, and avoids validating irrelevant state as the shared key space grows.

Scope Caveat

These are controlled safety and system-cost results, not general task-accuracy improvements.

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