Refuse the Harm, Complete the Task via Graph-of-Rules Planning for LLM-Enabled Robots

Large Language Models (LLMs) are increasingly used in embodied AI for robotic manipulation and planning, but their deployment in physical systems exposes vulnerabilities such as jailbreak attacks that can induce unsafe behavior. Existing inference-time defenses are mainly evaluated on short instructions containing a single hazard, whereas realistic tasks may interleave safe and unsafe sub-tasks, conceal hazardous steps, or combine individually safe actions into unsafe outcomes. Such compound instructions make it harder for a single safety decision to distinguish hazardous sub-tasks from legitimate ones, increasing the risk of either overlooking the hazard or rejecting the entire instruction. Thus, we introduce safe task completion, a task that requires an LLM-enabled robot to refuse the harmful part of an instruction while completing its legitimate part. To address this problem, we propose RuleGraph, a multi-agent Graph-of-Rules planning framework that distributes safety enforcement across multiple reasoning and verification stages. Five cooperating agents are used to ground general safety principles into world-specific rules, assess the instruction's sub-tasks in context, and derive a safe goal from the legitimate ones. Planning toward this goal is then organized as a graph of rule-specific nodes, where higher-level nodes inherit the union of their parents' rules, and candidate plans are progressively verified and aggregated until a single plan satisfies every relevant rule. In this way, RuleGraph reduces reliance on a single centralized safety decision. We evaluate RuleGraph on pure-attack and compound instructions across two benchmarks in two different environments using Attack Success Rate (ASR) and Task Success Rate (TSR). RuleGraph reduces ASR to 0% on both benchmarks while achieving the highest TSR among all methods, reaching 98.57% on the RoboGuard benchmark and 84.54% on our long-horizon compound instructions.