# ECP-0016: mDNS peer discovery for gossip

## Status
Draft

## Context
Manual gossip peers are a barrier for LAN onboarding. iroh already supports an mDNS-based address lookup, which can discover endpoints on the local network without external infrastructure.

## Decision
Enable iroh's mDNS address lookup and use it as a peer discovery layer for catalog gossip. When gossip starts (or sharing announces), we probe mDNS for a short window and merge any discovered endpoints into the peer list.

## Details
- Enable iroh feature `address-lookup-mdns`.
- Advertise `UserData = "every.channel"` for local discovery filtering.
- When gossip is started, probe for ~2 seconds and merge discovered endpoints with configured peers.
- mDNS discovery is best-effort; failures should not block manual peers.

## Consequences
- LAN nodes can connect and discover each other without copying addresses.
- Global discovery still requires at least one public peer.

## Follow-ups
- Add a UI indicator when mDNS peers are found.
- Evaluate relay-less LAN mode and mDNS-only sessions for local-first setups.
