Every time I spin up a new agent, I hit the same wall: how does it find anything else? It sounds like a boring infrastructure problem until you realize it shapes everything. Security, latency, whether your agent network actually scales, whether it works at all when half your nodes are sitting behind carrier-grade NAT. The answer you pick in week one tends to calcify fast. In 2026 there are really three approaches worth knowing about. DNS-SD is the old reliable for local setups. ACP-style centralized registries are what most multi-agent frameworks ship with. And then there's Pilot Protocol , which takes a different path entirely. None of them are universally correct. Here's how I think about the tradeoffs. DNS-SD: Fine Until You Leave the Building DNS-Based Service Discovery ( RFC 6763 ) is the tech behind Bonjour and mDNS. Services announce themselves on the local network with structured DNS records, clients query for them, and everything just works with zero configuration.…