FROST threshold signatures are fully backwards compatible — they produce standard BIP-340 Schnorr sigs. Every Nostr client already verifies them. No changes needed. But what if clients and relays could do more? Level 0: ✅ Valid Schnorr sig (today, everywhere) Level 1: 🧊 Client fetches kind 30078 epoch event → shows "FROST-managed identity" badge Level 2: ⚠️ Client checks frost-epoch tag → warns if event references old/revoked epoch Level 3: 🛡️ Relay indexes epoch chain → optionally rejects stale-epoch events Each level is opt-in. Level 0 works forever. Levels 1-3 add trust signals without breaking anything. Same adoption path as NIP-05: relays don't enforce it, clients display it, trust builds gradually. Working implementation exists. NIP draft incoming. 🧊