Gate fabric session endpoint through node config

agents/rap-node-agent/cmd/rap-node-agent/main.go

@@ -755,6 +755,15 @@ func startSyntheticMeshEndpoint(ctx context.Context, _ context.CancelFunc, cfg c
 			}
 			log.Printf("fabric_service_channel_access_event=%s", string(payload))
 		},
+		FabricSessionEnabled: cfg.MeshFabricSessionEnabled,
+		FabricSessionLogger: func(entry mesh.FabricSessionEventLogEntry) {
+			payload, err := json.Marshal(entry)
+			if err != nil {
+				log.Printf("fabric session event marshal failed: %v", err)
+				return
+			}
+			log.Printf("fabric_session_event=%s", string(payload))
+		},
 		RemoteWorkspaceFrameSink:  remoteWorkspaceFrameSink,
 		ProductionRoutes:          routes,
 		VPNPacketIngress:          vpnFabricIngress,
@@ -1639,6 +1648,15 @@ func applyRefreshedSyntheticMeshConfig(ctx context.Context, cfg config.Config, i
 			}
 			log.Printf("fabric_service_channel_access_event=%s", string(payload))
 		},
+		FabricSessionEnabled: cfg.MeshFabricSessionEnabled,
+		FabricSessionLogger: func(entry mesh.FabricSessionEventLogEntry) {
+			payload, err := json.Marshal(entry)
+			if err != nil {
+				log.Printf("fabric session event marshal failed: %v", err)
+				return
+			}
+			log.Printf("fabric_session_event=%s", string(payload))
+		},
 		RemoteWorkspaceFrameSink:  meshState.RemoteWorkspaceFrameSink,
 		ProductionRoutes:          loadedConfig.Routes,
 		VPNPacketIngress:          vpnFabricIngress,
@@ -2447,6 +2465,21 @@ func heartbeatPayload(cfg config.Config, identity state.Identity, meshState *syn
 		if cfg.MeshProductionForwardingEnabled || (meshState != nil && meshState.ProductionForwardingEnabled) {
 			payload.Capabilities["mesh_production_forwarding"] = true
 		}
+		if cfg.MeshFabricSessionEnabled {
+			payload.Metadata["fabric_session_endpoint_report"] = map[string]any{
+				"schema_version":    "rap.fabric_session_endpoint_report.v1",
+				"enabled":           true,
+				"transport":         "websocket_binary_frames",
+				"path":              "/mesh/v1/fabric/session/ws",
+				"auth":              "rap_fsn_token_with_optional_signed_authority",
+				"protocol":          "rap.fabric_data_session.v1",
+				"service_neutral":   true,
+				"traffic_isolation": "logical_streams",
+				"observed_at":       observedAt.UTC().Format(time.RFC3339Nano),
+			}
+			payload.Capabilities["fabric_session_websocket_endpoint"] = true
+			payload.Capabilities["fabric_data_session_v1"] = true
+		}
 		if meshState != nil && meshState.ConfigLoadError != "" {
 			payload.HealthStatus = "warning"
 		}