Summary

When a cron job with delivery.mode: "announce" fires while the main session is actively replying inside a Slack thread, the delivery inherits lastThreadId from the session and sends the cron output into the active thread instead of the top-level DM.

This causes unrelated content (research reports, reminders, proactive cron output) to appear inside whichever thread happens to be active at the moment — confusing and disruptive.

Root cause

resolveSessionDeliveryTarget() in targets.ts unconditionally inherits lastThreadId when the channel matches:

const threadId = channel && channel === lastChannel ? lastThreadId : void 0;
// ...
const resolvedThreadId = explicitThreadId ?? threadId;

The heartbeat/cron delivery path calls this via resolveHeartbeatDeliveryTarget() with mode: "heartbeat", but resolveSessionDeliveryTarget does not use this mode to suppress lastThreadId fallback.

Steps to reproduce

1. Configure a cron job with delivery.mode: "announce", delivery.channel: "slack", delivery.to: "user:<userId>"
2. Start a conversation in a Slack thread (reply to any message)
3. Wait for the cron job to fire while the thread conversation is active
4. Observe: cron output appears inside the active thread instead of top-level DM

Expected behavior

Cron announce delivery should send to the top-level DM channel, ignoring any active lastThreadId from the session. Thread targeting should only happen when explicitly configured (e.g., the proposed C12345:thread:TS syntax from #19903).

Suggested fix

In resolveSessionDeliveryTarget(), skip lastThreadId fallback when mode === "heartbeat":

const threadId = (params.mode !== "heartbeat" && channel && channel === lastChannel) 
  ? lastThreadId 
  : void 0;

This is a one-line change. The function already receives the mode parameter — it just needs to use it.

Environment

• OpenClaw version: 2026.2.23 (also present in 2026.2.22-2)
• Channel: Slack (Socket Mode)
• Cron job config: sessionTarget: "isolated", delivery.mode: "announce", delivery.to: "user:<id>"

Related

• [Feature]: Support Slack thread targeting for cron and heartbeat delivery #19903 — Feature request for explicit Slack thread targeting in cron/heartbeat delivery
• Telegram DM: lastThreadId cached from incoming messages causes reply delivery failures #13566 — Similar lastThreadId caching issue on Telegram DMs

AI-Assisted Disclosure

This issue was filed by an AI assistant (Claude, via OpenClaw). The root cause analysis was performed by reading the minified source in dist/reply-*.js and tracing the delivery flow through resolveHeartbeatDeliveryTarget → resolveSessionDeliveryTarget. The author (human operator) understands the issue and has experienced it repeatedly in production.