diff --git a/manifest.json b/manifest.json
index e20603c..926f3db 100644
--- a/manifest.json
+++ b/manifest.json
@@ -9,7 +9,7 @@
   ],
   "version": "0.3.2-alpha.3",
   "publisher": "latticenet",
-  "signature_ed25519": "cGr0AcT5LYLuaYxNIYfwL4jWZtYA04wgGjkhJGkbrk49uBDDqcKcIBT132BfJhhoNlKlb6+n8mokEDQJuAf5Cw==",
+  "signature_ed25519": "YW8Lzw9MqK7M0PzM5viOuJP4BiujmMHqGOJrIPdDd549zjrG9qIF0UVOsBlTNnnmtPltdDCeE57LQs/3RDQtAA==",
   "bundle": {
     "format": "tar+gzip",
     "digest_sha256": "8e6445836caf38fc7c58582601a98faf6b756587535c2c7e355e97a99de5756f"
@@ -86,7 +86,8 @@
             "base_url"
           ]
         }
-      ]
+      ],
+      "backing": "runtime"
     }
   ]
 }
diff --git a/system-go/conformance_test.go b/system-go/conformance_test.go
new file mode 100644
index 0000000..e838213
--- /dev/null
+++ b/system-go/conformance_test.go
@@ -0,0 +1,111 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"strings"
+	"testing"
+)
+
+// A manifest declares which methods a plugin exposes and — since `backing` — who
+// actually serves each one. This test holds the artifact to that promise.
+//
+// It exists because the promise used to go unchecked. Official plugins shipped signed
+// manifests declaring interface methods their own artifacts could not answer, and
+// lattice-server quietly answered them from an in-core handler instead. Nothing caught
+// it: every suite covered what the artifact DOES, never what the manifest CLAIMS. A
+// contract nobody verifies is a contract that drifts, and this is the gate that turns
+// that drift into a red build.
+//
+// Sub-Store is genuinely runtime-backed: its own artifact serves every method it
+// declares. This test is what keeps that true.
+func TestManifestInterfacesAreServedAsDeclared(t *testing.T) {
+	for _, iface := range loadManifestInterfaces(t) {
+		for _, method := range iface.Methods {
+			// An empty payload is rejected before any host call is attempted, so probing
+			// the dispatcher cannot reach the broker or the network. The stub host proves
+			// it: it fails the test if anything tries to call out.
+			rt := &runtime{host: refuseHostCalls{t}}
+			payload, err := json.Marshal(map[string]any{
+				"service": iface.Service,
+				"method":  method.Name,
+				"payload": map[string]any{},
+			})
+			if err != nil {
+				t.Fatalf("marshal call payload: %v", err)
+			}
+			resp := rt.handle(request{Action: "call", Payload: payload})
+			served := !refusedAsUnknown(resp)
+
+			switch iface.Backing {
+			case "runtime":
+				// This artifact is the declared owner, so it must at least recognise the
+				// method. Rejecting an empty payload is a real answer; not knowing the
+				// method at all is a broken promise.
+				if !served {
+					t.Errorf("%s/%s is declared runtime-backed, but this artifact does not serve it: %s",
+						iface.Service, method.Name, resp.Error)
+				}
+			case "core":
+				// The engine would live in lattice-server. If the artifact answers as well,
+				// the manifest names two owners for one method and the host has to guess.
+				if served {
+					t.Errorf("%s/%s is declared core-backed, but this artifact answers it too; backing must name exactly one owner",
+						iface.Service, method.Name)
+				}
+			case "":
+				t.Errorf("%s/%s declares no backing, so who serves it is left to inference",
+					iface.Service, method.Name)
+			default:
+				t.Errorf("%s/%s declares unknown backing %q", iface.Service, method.Name, iface.Backing)
+			}
+		}
+	}
+}
+
+// refuseHostCalls fails the test if the dispatcher reaches for the host. Probing which
+// methods exist must never have a side effect.
+type refuseHostCalls struct{ t *testing.T }
+
+func (h refuseHostCalls) call(method string, _ any) (json.RawMessage, error) {
+	h.t.Fatalf("conformance probe must not reach the host, but it called %q", method)
+	return nil, nil
+}
+
+// refusedAsUnknown separates "I do not implement this" from "I implement this and your
+// payload is wrong". Only the former means the artifact cannot serve the method — a
+// validation error proves the method is wired up.
+func refusedAsUnknown(resp response) bool {
+	if resp.OK {
+		return false
+	}
+	return strings.Contains(resp.Error, "unsupported action") ||
+		strings.Contains(resp.Error, "unsupported service") ||
+		strings.Contains(resp.Error, "unsupported method")
+}
+
+type manifestInterface struct {
+	Service string `json:"service"`
+	Backing string `json:"backing"`
+	Methods []struct {
+		Name string `json:"name"`
+	} `json:"methods"`
+}
+
+func loadManifestInterfaces(t *testing.T) []manifestInterface {
+	t.Helper()
+	raw, err := os.ReadFile("../manifest.json")
+	if err != nil {
+		t.Fatalf("read manifest: %v", err)
+	}
+	var m struct {
+		Interfaces []manifestInterface `json:"interfaces"`
+	}
+	if err := json.Unmarshal(raw, &m); err != nil {
+		t.Fatalf("parse manifest: %v", err)
+	}
+	if len(m.Interfaces) == 0 {
+		t.Fatal("manifest declares no interfaces to verify")
+	}
+	return m.Interfaces
+}