epp: read endpoint type through an attribute, not the metadata field

Publish the discovered endpoint type as an endpoint attribute at creation and read
it through EndpointTypeOf, so multi-cluster-aware plugins query the attribute map
while every other consumer is unaffected. Only EPP is stamped; absence reads as
engine. The metadata Type field stays as the discovery transport but no longer
participates in Equal, since type is a trait rather than identity.

Signed-off-by: Sam Batschelet <sbatsche@redhat.com>

Author: hexfusion

pkg/epp/framework/interface/datalayer/endpoint.go

@@ -61,6 +61,11 @@ func NewEndpoint(meta *EndpointMetadata, metrics *Metrics) *ModelServer {
 	}
 	ep.UpdateMetadata(meta)
 	ep.UpdateMetrics(metrics)
+	// Discovery carries the type on metadata. Publish EPP as an attribute that
+	// consumers read through EndpointTypeOf. Absence reads as engine.
+	if meta.Type == EndpointTypeEPP {
+		SetEndpointType(ep, meta.Type)
+	}
 	return ep
 }
 

pkg/epp/framework/interface/datalayer/endpoint_metadata.go

@@ -58,7 +58,9 @@ type EndpointMetadata struct {
 	Port        string
 	MetricsHost string
 	Labels      map[string]string
-	Type        EndpointType
+	// Type carries the discovered endpoint type to endpoint creation, where it is
+	// published as an attribute. Read it through EndpointTypeOf, not this field.
+	Type EndpointType
 	// RankIndex is this endpoint's position in the pool's TargetPorts,
 	// identifying the pod-local rank in multi-port deployments.
 	RankIndex int
@@ -108,7 +110,6 @@ func (epm *EndpointMetadata) Equal(other *EndpointMetadata) bool {
 		epm.NodeAddress == other.NodeAddress &&
 		epm.Port == other.Port &&
 		epm.MetricsHost == other.MetricsHost &&
-		epm.Type == other.Type &&
 		epm.RankIndex == other.RankIndex &&
 		maps.Equal(epm.Labels, other.Labels)
 }

pkg/epp/framework/interface/datalayer/endpoint_metadata_test.go

@@ -129,12 +129,6 @@ func TestEndpointMetadataEqual(t *testing.T) {
 				meta.Labels["app"] = "sglang"
 			},
 		},
-		{
-			name: "type",
-			mutate: func(meta *EndpointMetadata) {
-				meta.Type = EndpointTypeEPP
-			},
-		},
 		{
 			name: "rank index",
 			mutate: func(meta *EndpointMetadata) {

pkg/epp/framework/interface/datalayer/endpoint_type.go

@@ -0,0 +1,42 @@
+/*
+Copyright 2026 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package datalayer
+
+// EndpointTypeAttrKey is the attribute under which an endpoint's type is stored.
+// Type is carried as an attribute rather than a first-class identity field so the
+// contract stays loose while the concept settles.
+const EndpointTypeAttrKey = "llm-d.ai/endpoint-type"
+
+// endpointTypeAttr is the Cloneable stored under EndpointTypeAttrKey.
+type endpointTypeAttr EndpointType
+
+func (t endpointTypeAttr) Clone() Cloneable { return t }
+
+// SetEndpointType records an endpoint's type in its attributes.
+func SetEndpointType(ep Endpoint, t EndpointType) {
+	ep.GetAttributes().Put(EndpointTypeAttrKey, endpointTypeAttr(t))
+}
+
+// EndpointTypeOf returns an endpoint's type, defaulting to engine when unset.
+func EndpointTypeOf(ep Endpoint) EndpointType {
+	if v, ok := ep.GetAttributes().Get(EndpointTypeAttrKey); ok {
+		if t, ok := v.(endpointTypeAttr); ok {
+			return EndpointType(t)
+		}
+	}
+	return EndpointTypeEngine
+}