A forum topic is a named sub-thread inside a Telegram supergroup that has forum mode turned on — the Chat carries is_forum: true, and every message in the group belongs to exactly one topic instead of one shared timeline. Autogram publishes to channels, not to supergroups, so it never creates or posts into a topic directly; the concept matters to Autogram users through the discussion group a channel can link, which Telegram may organize into topics once its admin turns forum mode on.
Forum mode is a setting a supergroup's administrator switches on, recorded on the Chat object as is_forum: true. Once it is on, the single message stream splits into named topics — each with its own title and icon — and every new message belongs to one of them rather than to the group as a whole. Telegram creates a default 'General' topic to hold messages that predate the switch and anything not filed elsewhere.
The Message object exposes message_thread_id, which names the topic a given message belongs to; a bot reading the group’s updates uses this field to tell which conversation a message is part of. Telegram also posts a service message for each topic lifecycle event — ForumTopicCreated, ForumTopicEdited, ForumTopicClosed, ForumTopicReopened — plus general_forum_topic_hidden and general_forum_topic_unhidden for the default topic specifically, so a bot can track the topic list without polling for it.
Autogram's product surface is the channel, not the group behind it — the automation, scheduling, and AI generation this glossary describes elsewhere all target the channel a post is sent to. A channel can link a discussion group for comments, though, and if that group has forum mode on, Telegram — not Autogram — decides which topic a given comment thread lands in. Autogram's publishing pipeline does not set message_thread_id, because it has no topic to choose: it posts to the channel, and the linked group's topic structure is a property of the group Autogram does not manage.
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