Summary

When replying to messages in a Telegram forum group topic, the reply is processed correctly by the agent but the outbound sendMessage call to Telegram only includes chat_id (the group), omitting message_thread_id (the topic). The message lands in the group's main chat instead of the specific topic, making it invisible to users browsing that topic.

Environment

• OpenClaw: 2026.5.6 (issue also present on 2026.5.4, 2026.5.4-beta.3)
• Channel: Telegram polling
• Group type: Telegram Forum (supergroup with is_forum: true)
• Config: channels.telegram.groups["-1003759908827"].topics configured with per-topic systemPrompts

Reproduction

1. Configure a Telegram forum group with topics in openclaw.json:

{
  "channels": {
    "telegram": {
      "groups": {
        "-1003759908827": {
          "requireMention": false,
          "topics": {
            "55": { "systemPrompt": "..." }
          }
        }
      }
    }
  }
}

2. Send a message in topic 55 from Telegram
3. Agent receives the message, generates a reply
4. sessions.json shows correct deliveryContext:

{
  "channel": "telegram",
  "to": "telegram:-1003759908827",
  "accountId": "default",
  "threadId": 55
}

5. Gateway log shows:

[telegram] sendMessage ok chat=-1003759908827 message=21230

Expected: API call includes message_thread_id: 55 → reply appears in topic 55
Actual: Only chat_id sent → reply appears in group main chat (not visible in topic)

Evidence

• systemSent: true in sessions.json — Gateway believes it sent successfully
• lastThreadId: 55 — threadId is tracked in session state
• deliveryContext.threadId: 55 — correct value in delivery context
• But the Telegram sendMessage log shows no threadId parameter being passed
• The reply message (21230) is visible in the group's main chat, not in topic 55

When It Broke

Last successful topic reply: 2026-05-04 15:33 (message 21166)
Around the same time, the active-memory plugin started failing with:

Error: Bundled plugin dirName must be a single directory: -1003759908827:topic:55

The active-memory plugin is now disabled, but the topic delivery issue persists even after:

• Restarting Gateway
• Deleting and re-creating the topic 55 session from sessions.json
• Upgrading from 2026.5.4 → 2026.5.6

Hypothesis

The session delivery path for Telegram forum topics either:

1. Never correctly mapped threadId → message_thread_id for the outbound sendMessage call, OR
2. A regression somewhere between working state and 2026.5.4 broke the threadId pass-through in the Telegram channel delivery layer

Workaround

None currently. Topic replies are silently lost to the group main chat.