test(32.1-05): keep implied MCP scopes off the subject

- MCPDispatch expands the credential and leaves subject.Scopes unchanged

mcp_implies_test.go

@@ -154,6 +154,30 @@ func TestMCPImpliesWriteDoesNotGrantRead(t *testing.T) {
 	}
 }
 
+// TestMCPImpliesNotPersisted pins that MCPDispatch expands scopes only on
+// the credential it returns. The subject's grant slice is the same backing
+// array afterwards.
+func TestMCPImpliesNotPersisted(t *testing.T) {
+	_, guard := impliesApp(t, impliesServersRead())
+	ctx := context.Background()
+	subject := pact.MCPSubject{Guard: "user", UserID: 7, ClientID: "oauth-client", Scopes: []string{"read"}}
+	orig := subject.Scopes
+	dispatch, err := guard.MCPDispatch(ctx, subject, "GET")
+	if err != nil {
+		t.Fatal(err)
+	}
+	credential, isToken := dispatch.Credential.(*models.APIToken)
+	if !isToken || !credential.HasScope("servers:read") || !credential.HasScope("read") {
+		t.Fatalf("credential = %+v, want the expanded scopes on the credential only", dispatch.Credential)
+	}
+	if len(subject.Scopes) != 1 || &subject.Scopes[0] != &orig[0] || subject.Scopes[0] != "read" {
+		t.Fatalf("subject.Scopes = %v, want the original grant slice", subject.Scopes)
+	}
+	if slices.Contains(subject.Scopes, "servers:read") {
+		t.Fatal("implied name was written onto subject.Scopes")
+	}
+}
+
 // TestMCPImpliesAlreadyPresent does not append a declared name the grant
 // already holds, and does not append a catalog name whose Implies is empty.
 func TestMCPImpliesAlreadyPresent(t *testing.T) {