PairCast: Direct Counterfactual Packet Value for Multirate Swarm Communication

Freeze a swarm one control cycle before an occluded neighbor becomes collision-relevant: decoding a short update can redirect several receivers, while an equally novel packet can leave every action unchanged. Scheduling with an integrated controller and packet format therefore requires the control consequence of each available rate, not packet salience alone. Counterfactual packet value (CPV) is the delivery-adjusted, sender-local return gain per attempted bit between successful decoding of a candidate prefix and continued silence. PairCast estimates CPV for nested 1–8-bit prefixes by branching a permutation-equivariant neighborhood world model into paired multi-step futures, then admits the highest-density prefix through a shared reservation price and a one-step-lagged occupancy signal. On 20-agent formation under occlusion, 30-agent dynamic coverage, and 10-versus-3 pursuit-evasion, it reaches 95.9–97.4% normalized return with roughly 48% of Dense Broadcast traffic; at the matched 48.2% operating point, it leads Adaptive self-triggering by 1.9–3.4 taskwise points and a SchedNet-style multirate scheduler by 2.1 pooled points [1.0, 3.1]. Consequence estimation is predictive on 45000 held-out interventions (0.66 Spearman correlation, 78.4% sign accuracy, and 0.18 normalized decision regret), while replacing it with uncertainty scoring costs 4.8 return points and reducing its paired horizon from five steps to one costs 2.1. Shared-prefix execution retains a 1.6-point advantage within an 8.9 ms A100 p99 envelope, and matched-load gains remain 1.8–2.2 points throughout the communication-scarce 40–60% regime. Directly valuing how a decode changes the team's future provides a practical scheduling principle for multirate coordination under shared-medium contention.