`message_thread_id` is silently ignored when the target topic was deleted (in private chat)

[foremtehan]

Hi,

I noticed an issue with forum topics and message_thread_id.

If a topic is deleted manually in the bot's private chat, and the bot later sends a message using the old `message_thread_id, the API does not return any error. Instead, the parameter seems to be ignored silently and the message is sent to the main chat.

This makes it impossible for bots to reliably detect that the topic no longer exists and recreate it when needed.

Steps:

1. Enable topic mode for bot private chats
2. Create a topic using telegram bot api
3. delete that topic
4. now sendMessage and set using old message_thread_id from number 2

You'll see telegram ignores the message_thread_id and sends message to the main chat.

If you do this in the groups you'll get this error: Bad Request: message thread not found

[levlam]

There can be some cache issues. Have you tried to wait for at least a minute after topic deletion before sending a message there?

[foremtehan]

It's been half an hour since then, but it isn't showing any errors.