fix(messages): normalize webhook reply references

backend/internal/handler/webhook/incoming_persister.go

@@ -3,7 +3,9 @@ package webhook
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
+	"strings"
 	"time"
 
 	"github.com/google/uuid"
@@ -538,8 +540,27 @@ func (p *IncomingPersister) createMessage(ctx context.Context, tx *gorm.DB, inbo
 	if len(msg.Attachments) > 0 {
 		contentAttrs["attachments"] = msg.Attachments
 	}
-	if msg.ReplyToID != "" {
-		contentAttrs["in_reply_to"] = msg.ReplyToID
+	if replyToExternalID := strings.TrimSpace(msg.ReplyToID); replyToExternalID != "" {
+		// Chatwoot stores provider reply references as in_reply_to_external_id,
+		// then resolves the same-conversation message by source_id before save.
+		// Keep in_reply_to strictly as the internal numeric message ID expected by
+		// the dashboard and its cursor-based message API.
+		var replyMessage model.Message
+		err := tx.WithContext(ctx).
+			Where("conversation_id = ? AND source_id = ?", conversation.ID, replyToExternalID).
+			First(&replyMessage).Error
+		if err == nil {
+			contentAttrs["in_reply_to"] = replyMessage.ID
+			contentAttrs["in_reply_to_external_id"] = replyMessage.SourceID
+		} else if errors.Is(err, gorm.ErrRecordNotFound) {
+			// Match Chatwoot's InReplyToMessageBuilder: unresolved references
+			// are normalized to null instead of being persisted as an invalid
+			// internal message ID.
+			contentAttrs["in_reply_to"] = nil
+			contentAttrs["in_reply_to_external_id"] = nil
+		} else {
+			return nil, err
+		}
 	}
 	message := model.Message{
 		ConversationID:       conversation.ID,