Bug Report: Slack Thread Session Generates Responses But Fails to Deliver

Summary

Slack thread sessions generate assistant responses successfully (visible in session transcript) but the responses are never delivered to Slack. Direct Slack API calls work fine, proving the issue is in OpenClaw's thread reply delivery path.

Environment

• OpenClaw version: 2026.5.4 (325df3e)
• Channel: Slack (socket mode)
• Session type: Thread session (topic_id-based)

Reproduction

1. Start a thread in a Slack channel (agent posts first message successfully)
2. User replies in thread
3. Agent generates response (visible in session transcript with stopReason: "stop")
4. Response never appears in Slack thread
5. Repeating pings results in same pattern: responses generated but not delivered

Evidence

Session Transcript Shows Successful Generation

{"ts":"2026-05-05T20:44:55.251Z","role":"user","content":"<@U0ATVCXNC9Y> (Ghosty)"}
{"ts":"2026-05-05T20:44:57.797Z","role":"assistant","content":"I'm here, Kennan! What do you need? 🐙","stop":"stop"}
{"ts":"2026-05-05T20:45:17.193Z","role":"user","content":"<@U0ATVCXNC9Y> (Ghosty)"}
{"ts":"2026-05-05T20:45:19.611Z","role":"assistant","content":"Still here, Kennan! 🐙 You've pinged me 4 times now...","stop":"stop"}

Slack Thread Only Has User Messages

[20:31:23] 👤 Kennan: <@U0ATVCXNC9Y>
[20:44:51] 👤 Kennan: <@U0ATVCXNC9Y>
[20:45:13] 👤 Kennan: <@U0ATVCXNC9Y>

(No bot responses between 03:19 and test message sent via direct API)

Direct Slack API Works

Manual chat.postMessage to the same thread via curl succeeded immediately, proving the Slack API and bot token are functional.

Gateway Diagnostics

At 20:39:10, gateway showed:

[diagnostic] liveness warning: reasons=event_loop_delay
eventLoopDelayMaxMs=6954.2
eventLoopUtilization=0.419

However, this doesn't explain why ONLY thread sessions fail while DM sessions work fine (user confirmed DMs in same timeframe were being delivered).

Related Issue

This may be related to #78059 (thread session reset on idle loses messages), but appears to be a separate delivery path failure rather than a session lifecycle issue.

Thread Details

• Channel: C0AUJJW6Q3H (#ai_share)
• Thread ts: 1777951172.213659
• Session key: agent:main:slack:channel:c0aujjw6q3h:thread:1777951172.213659
• Session file: 55a9502a-3efd-435b-9d35-a9ca9a3dc629-topic-1777951172.213659.jsonl

Impact

• High: Thread conversations completely broken
• Workaround: None (responses silently lost)
• DMs continue to work