diff --git a/cmd/api/cmd_test.go b/cmd/api/cmd_test.go
index e42d23e..145894a 100644
--- a/cmd/api/cmd_test.go
+++ b/cmd/api/cmd_test.go
@@ -189,6 +189,30 @@ func TestAPISpecCmd_Good_ContactFlagsPopulateSpecInfo(t *testing.T) {
 	}
 }
 
+func TestSpecGroupsIter_Good_DeduplicatesExtraBridge(t *testing.T) {
+	snapshot := api.RegisteredSpecGroups()
+	api.ResetSpecGroups()
+	t.Cleanup(func() {
+		api.ResetSpecGroups()
+		api.RegisterSpecGroups(snapshot...)
+	})
+
+	group := specCmdStubGroup{}
+	api.RegisterSpecGroups(group)
+
+	var groups []api.RouteGroup
+	for g := range specGroupsIter(group) {
+		groups = append(groups, g)
+	}
+
+	if len(groups) != 1 {
+		t.Fatalf("expected duplicate extra group to be skipped, got %d groups", len(groups))
+	}
+	if groups[0].Name() != group.Name() || groups[0].BasePath() != group.BasePath() {
+		t.Fatalf("expected original group to be preserved, got %s at %s", groups[0].Name(), groups[0].BasePath())
+	}
+}
+
 func TestAPISpecCmd_Good_TermsOfServiceFlagPopulatesSpecInfo(t *testing.T) {
 	root := &cli.Command{Use: "root"}
 	AddAPICommands(root)
diff --git a/cmd/api/spec_groups_iter.go b/cmd/api/spec_groups_iter.go
index ce910e5..5c5a87a 100644
--- a/cmd/api/spec_groups_iter.go
+++ b/cmd/api/spec_groups_iter.go
@@ -13,15 +13,29 @@ import (
 // existing ordering guarantees.
 func specGroupsIter(extra goapi.RouteGroup) iter.Seq[goapi.RouteGroup] {
 	return func(yield func(goapi.RouteGroup) bool) {
+		seen := map[string]struct{}{}
 		for group := range goapi.RegisteredSpecGroupsIter() {
+			key := specGroupIterKey(group)
+			seen[key] = struct{}{}
 			if !yield(group) {
 				return
 			}
 		}
 		if extra != nil {
+			if _, ok := seen[specGroupIterKey(extra)]; ok {
+				return
+			}
 			if !yield(extra) {
 				return
 			}
 		}
 	}
 }
+
+func specGroupIterKey(group goapi.RouteGroup) string {
+	if group == nil {
+		return ""
+	}
+
+	return group.Name() + "\x00" + group.BasePath()
+}