diff --git a/backend/internal/api/notes.go b/backend/internal/api/notes.go
index 219f600..f43c924 100644
--- a/backend/internal/api/notes.go
+++ b/backend/internal/api/notes.go
@@ -732,12 +732,26 @@ func (s *NoteWriteService) CreateReply(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if req.ParentURI == "" || req.ParentCID == "" {
-		WriteBadRequest(w, "parentUri and parentCid are required")
+	if req.ParentURI == "" {
+		WriteBadRequest(w, "parentUri is required")
 		return
 	}
-	if req.RootURI == "" || req.RootCID == "" {
-		WriteBadRequest(w, "rootUri and rootCid are required")
+	if req.ParentCID == "" {
+		req.ParentCID = s.resolveCID(r, req.ParentURI)
+	}
+	if req.ParentCID == "" {
+		WriteBadRequest(w, "parentCid is required and could not be resolved")
+		return
+	}
+	if req.RootURI == "" {
+		WriteBadRequest(w, "rootUri is required")
+		return
+	}
+	if req.RootCID == "" {
+		req.RootCID = s.resolveCID(r, req.RootURI)
+	}
+	if req.RootCID == "" {
+		WriteBadRequest(w, "rootCid is required and could not be resolved")
 		return
 	}
 	if req.Text == "" {
diff --git a/web/src/views/content/AnnotationDetail.tsx b/web/src/views/content/AnnotationDetail.tsx
index 21f733e..9a92414 100644
--- a/web/src/views/content/AnnotationDetail.tsx
+++ b/web/src/views/content/AnnotationDetail.tsx
@@ -153,14 +153,14 @@ export default function AnnotationDetail({
         : targetUri;
       const parentCid = replyingTo ? replyingTo.cid : annotation.cid;
 
-      if (!parentUri || !parentCid || !annotation.cid)
+      if (!parentUri)
         throw new Error("Missing parent info");
 
       await createReply(
         parentUri,
-        parentCid,
+        parentCid || "",
         targetUri,
-        annotation.cid,
+        annotation.cid || "",
         replyText,
       );