openclaw - 💡(How to fix) Fix Slack: thread replies should optionally route to parent session (thread.sessionMode) [1 comments, 2 participants]

Problem

When a Slack message has a thread_ts, Clawdbot creates a separate session key (baseKey:thread:{threadTs}) via resolveThreadSessionKeys() in routing/session-key.js. This means:

1. Any bot reply using replyTo creates a Slack thread
2. Every subsequent message in that thread spawns a separate session per bot listening to the channel
3. Each separate session has its own context window and burns its own tokens
4. In multi-bot setups, a single threaded reply can double or triple token spend

This is the #1 token waste issue for multi-agent Slack deployments.

Current behavior

• resolveThreadSessionKeys() always appends :thread:{threadTs} to the session key (Slack)
• Discord already passes useSuffix: false, routing thread messages to the parent session
• channels.slack.thread.inheritParent only sets parentSessionKey — it does NOT prevent the separate session from being created
• channels.slack.replyToMode: "off" prevents auto-threading but agents can still thread via replyTo in message tool calls

Proposed solution

Add channels.slack.thread.sessionMode config:

{
  channels: {
    slack: {
      thread: {
        sessionMode: "parent"  // "parent" | "separate" (default: "parent")
      }
    }
  }
}

• "parent" (proposed default): Thread messages route to the parent channel session. Same behavior as Discord's useSuffix: false. Thread context is still available in the message metadata but doesn't create a separate session.
• "separate" (current behavior): Thread messages create separate sessions as they do today.

Implementation

In slack/monitor/message-handler/prepare.js, pass useSuffix based on the new config:

const threadKeys = resolveThreadSessionKeys({
    baseSessionKey,
    threadId: isThreadReply ? threadTs : undefined,
    parentSessionKey: isThreadReply && ctx.threadInheritParent ? baseSessionKey : undefined,
    useSuffix: ctx.threadSessionMode !== "parent",  // NEW
});

Per-message opt-in (stretch goal)

For cases where separate thread sessions ARE useful (e.g., parallel work items), allow agents to request thread separation explicitly via a message tag or tool parameter like separateSession: true. This inverts the current model: threads are merged by default, separated only on intent.

Environment

• Clawdbot version: 2026.1.24-3+
• Channel: Slack (Socket Mode)
• Multi-agent setup: 5 bots on 2 servers

Related

• openclaw/openclaw#50984 (thread reply session cost)
• Discord already uses useSuffix: false for threads