diff --git a/tailcfg/tailcfg.go b/tailcfg/tailcfg.go
index de34cc7f0..0043c0ecd 100644
--- a/tailcfg/tailcfg.go
+++ b/tailcfg/tailcfg.go
@@ -1462,6 +1462,13 @@ const (
 	// user groups as Kubernetes user groups. This capability is read by
 	// peers that are Tailscale Kubernetes operator instances.
 	PeerCapabilityKubernetes PeerCapability = "tailscale.com/cap/kubernetes"
+
+	// PeerCapabilityRelay grants the ability for a peer to allocate relay
+	// endpoints.
+	PeerCapabilityRelay PeerCapability = "tailscale.com/cap/relay"
+	// PeerCapabilityRelayTarget grants the current node the ability to allocate
+	// relay endpoints to the peer which has this capability.
+	PeerCapabilityRelayTarget PeerCapability = "tailscale.com/cap/relay-target"
 )
 
 // NodeCapMap is a map of capabilities to their optional values. It is valid for