How to identify if a Slack message is a thread reply?

Question

Using the ts of a Slack message (e.g. 1234567890.123456), how can I know if that message is reply in a thread or a regular message in a channel?

• If if is in a thread, I want to reply to the thread.
• Otherwise, I want to start a thread (post a first reply).

This is not about how to post a message in a thread, which is easy. It is about how to identify whether a specific message is a regular message or a thread reply (because surprisingly, the Slack API documentation makes this extremely confusing).

More specifically, Slack mentions in multiple places to use the conversation.history endpoint in order to retrieve a single message, but that method is unable to retrieve messages from threads.

See more details in this GitHub issue.

• devlin carnate: This question is similar to: How to make my slackbot reply in a thread, instead of to entire channel in Slack. If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem.
• devlin carnate: Also, here
• Marco Roy: Yeah, I saw those. It is not the same problem. I'll clarify the question.

Answer 1

The conversations.replies API endpoint is the way to go.

It's very simple, using the ts of any message:
https://slack.com/api/conversations.replies?channel=C1C1C1C1C1&ts=1234567890.123456

• If the message is a regular message without thread/replies, the response will only contain ts and no thread_ts.

  • You can then use the ts as the thread_ts to post the first reply.

• If the message is a regular message with a thread/replies, the response will contain ts as well as thread_ts, and both values will be the same (along with other things like reply_count, reply_users_count, and latest_reply).

  • You can then use the ts / thread_ts to add a new reply.

• If the message is a reply within a thread, the response will contain ts as well as thread_ts, and the values will be different (and there won't be any other things like reply_count, reply_users_count, and latest_reply).

  • You can then use the thread_ts to add a new reply.