🤔 Does the communication topology for LLM multi-agent systems really need to be generated from scratch every single time? A team at UCLA questioned that very assumption.
Title: Codebook Agent: Amortized Topology Design for LLM Multi-Agent Systems
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❓ Why have people assumed agent communication topologies need to be searched by a generative model every time?
💡 Turns out they may not need to be. The topologies that survive reward filtering converge to only about 6 distinct graphs, even as the codebook size grows from 8 to 64 — the design space is far smaller than it looks.
❓ Wouldn't making the graph sparser (fewer edges) cut down token usage?
💡 The opposite happens. Edge count correlates with token cost at r=-0.4 — sparser graphs actually use more tokens. Structural "cheapness" doesn't match measured cost.
❓ What's wrong with scoring candidate topologies using a GNN, as prior work does?
💡 For homogeneous agent teams (common in real deployments), the GNN's message passing treats every adjacency matrix as the same input, so it can't tell candidates apart — a real failure mode, not just a minor gap.
❓ So how well does Codebook Agent actually work once it swaps generation for selection?
💡 By compressing topologies into 16 codes via a VQ-AE and picking candidates with a reward-weighted MLP plus a proxy trained on real measured costs, it cuts generation latency from 301-396ms down to 2.4ms — a 125-158x speedup — while improving accuracy by 1.6 points on average over the prior best method and cutting tokens by 21.9-33.2%.
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