Problem

The Slack implicitMention check in the message handler only triggers when the bot is the root/parent message author of a thread:

const implicitMention = Boolean(!isDirectMessage && ctx.botUserId && message.thread_ts && message.parent_user_id === ctx.botUserId);

This means:

1. User @mentions bot in a channel → bot responds (creates thread)
2. User replies in thread without @mention → bot receives it ✅ (only if bot authored the root message)
3. User starts a thread, bot gets @mentioned and replies → user follows up without @mention → bot does NOT receive it ❌

Scenario 3 is very common — the user starts a conversation, the bot joins via @mention, and then the user expects to continue naturally without re-mentioning.

Expected behavior

implicitMention should be true when the bot has any prior reply in the thread, not just when it is the parent_user_id.

Suggested fix

Check thread participation by querying whether the bot has posted in the thread (via conversations.replies or by tracking thread participation in the session store). Something like:

const implicitMention = Boolean(
  !isDirectMessage && ctx.botUserId && message.thread_ts && (
    message.parent_user_id === ctx.botUserId ||
    await ctx.hasBotRepliedInThread(message.channel, message.thread_ts)
  )
);

Alternatively, a config option like thread.autoFollow: true (as suggested in #23064) that enables this behavior.

Related issues

• Slack: bot should auto-follow threads it has participated in #23064 (Slack: bot should auto-follow threads it has participated in)
• slack: keep requireMention thread follow-ups when thread session is active #21108 (slack: keep requireMention thread follow-ups when thread session is active)

Environment

• OpenClaw version: 2026.2.23
• Channel: Slack (Socket Mode)
• Config: requireMention: true, thread.inheritParent: true, replyToMode: all