fix(api): enforce correct message type for replies in personal notes (#58)

fluxer_api/src/channel/services/message/MessageSendService.ts

@@ -907,7 +907,7 @@ export class MessageSendService {
 			messageId,
 			channelId,
 			user,
-			type: MessageTypes.DEFAULT,
+			type: this.getMessageTypeForRequest(data),
 			content: data.content,
 			flags: data.flags ? data.flags & SENDABLE_MESSAGE_FLAGS : 0,
 			embeds: data.embeds,

tests/integration/personal_notes_reply_type_test.go

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2026 Fluxer Contributors
+ *
+ * This file is part of Fluxer.
+ *
+ * Fluxer is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Fluxer is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with Fluxer. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package integration
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+)
+
+const personalNotesMessageTypeReply = 19
+
+// TestPersonalNotesReplyType ensures replies sent from the Personal Notes channel
+// are serialized with the REPLY message type.
+func TestPersonalNotesReplyType(t *testing.T) {
+	client := newTestClient(t)
+	account := createTestAccount(t, client)
+	ensureSessionStarted(t, client, account.Token)
+
+	channelID := parseSnowflake(t, account.UserID)
+	originalMessage := sendChannelMessage(t, client, account.Token, channelID, "Original personal note")
+
+	replyPayload := map[string]any{
+		"content": "Replying in personal notes",
+		"message_reference": map[string]any{
+			"message_id": originalMessage.ID,
+			"channel_id": account.UserID,
+			"type":       0,
+		},
+	}
+
+	resp, err := client.postJSONWithAuth(
+		fmt.Sprintf("/channels/%d/messages", channelID),
+		replyPayload,
+		account.Token,
+	)
+	if err != nil {
+		t.Fatalf("failed to post personal notes reply: %v", err)
+	}
+	assertStatus(t, resp, http.StatusOK)
+
+	var reply struct {
+		ID               string `json:"id"`
+		Type             int    `json:"type"`
+		MessageReference *struct {
+			MessageID string `json:"message_id"`
+			ChannelID string `json:"channel_id"`
+		} `json:"message_reference"`
+	}
+	decodeJSONResponse(t, resp, &reply)
+
+	if reply.Type != personalNotesMessageTypeReply {
+		t.Fatalf("expected personal notes reply type %d but got %d", personalNotesMessageTypeReply, reply.Type)
+	}
+
+	if reply.MessageReference == nil {
+		t.Fatalf("expected message_reference to be present in personal notes reply")
+	}
+
+	if reply.MessageReference.MessageID != originalMessage.ID {
+		t.Fatalf("personal notes reply referenced wrong message: expected %s, got %s", originalMessage.ID, reply.MessageReference.MessageID)
+	}
+}