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topics

The topic of a message, the four ways a topic starts, the order that picks the active topic, and the MCP tools for topic sessions. Topics explains the concept.

Three records carry topic state

record	field	meaning
message	`topic`	The topic of the message. An empty string is the default topic.
chat	sticky topic	The topic pin of a chat. Empty means no pin. `store/chats.go:272`
session	`(folder, topic)`	One Claude session for each folder and topic pair.

The chat record also holds the sticky group, a folder pin. It is a different pin and appears here only to tell the two apart. schema lists the full store.

Four sources set a topic

An inline #name prefix: A message whose text starts with #name opens the topic #name. The regex is ^\s*#(\w[\w-]*), rePrefixHash in routd/steer.go:443. handlePrefixLayer removes the prefix, writes the rest as a new message with Topic = "#" + name and queues the chat.
A bare #name message: A message that is only #name sets the sticky topic of the chat. A message that is only # clears it. handleStickyCommand in routd/steer.go:49 replies topic → <name> or topic reset to default.
/new and /new #name: /new alone clears the session of the default topic. /new #name [rest] clears the session of #name, then writes #name rest as a new inbound message, which goes through the prefix path. cmdNew in routd/steer.go:411.
Platform threads: Discord: a message in a thread gets the thread ID as its topic, under the JID of the parent channel, in chatAndTopic, discd/bot.go:304. Telegram: a message in a forum topic gets the MessageThreadID as its topic, teled/bot.go:396. Slack: a thread uses its thread_ts. Other adapters leave the topic empty.

A sticky topic wins over the topic of the message

When routd forms a turn, effectiveTopic in routd/loop.go:681 picks the topic:

func (l *Loop) effectiveTopic(chatJID, msgTopic string) string {
	if _, sticky := l.db.StickyState(chatJID); sticky != "" {
		return sticky
	}
	return msgTopic
}

The sticky topic of the chat, if it is not empty.
The topic of the message, from the prefix or from a platform thread.
The empty string, the default topic.

The result selects the Claude session of the turn.

A sticky topic also wins over an inline prefix. When the chat is pinned to #current, a message with #other still runs under #current. Send a bare # to clear the pin first.

Two MCP tools act on topic sessions

reset_session(groupFolder): Clears the Claude session of a folder, so the next message starts with a new context. The caller must hold mcp:reset_session with a scope that covers groupFolder. Registered in ipc/ipc.go:1738.
inspect_session(topic?, limit?): Returns the current session_id of the own folder and the topic, with recent session_log rows. limit defaults to 10; a value of 0 or less, or over 100, gives the default. Registered in ipc/inspect.go.

inject_message writes an inbound message, and the next turn applies the sticky and prefix rules to it as to any other message. No set_topic or get_topic tool exists. A sticky change goes through the #name chat command.

Observed messages ignore the topic

Every turn also gets the observed messages of its folder. store.ObservedSince in store/message_folders.go:284 reads them by folder and cursor, not by topic, up to OBSERVE_WINDOW_MESSAGES messages and OBSERVE_WINDOW_CHARS characters. routd calls it in routd/prompt_db.go:82. So a turn in topic #tickets-42 of folder support sees the recent observed messages of support, whatever their topic. For strict isolation, use separate folders.

Operators change topics from the chat

Reset a topic: /new #name clears that session. /new clears the session of the default topic.
Pin or unpin a topic: Send a bare #name to pin and a bare # to clear.
Inspect from the agent: Call inspect_session with a topic.
Reset from the agent: Call reset_session with the target groupFolder.

No arizuko subcommand sets or reads topics. Topics has the narrative, routing shows how a chat reaches a folder, and MCP tools lists every tool.