fix(cron): use message_thread_id for private-chat forum topics (#55265)

[nniicckk6]

Problem

PR #50023 blanket-switched all Telegram private-chat cron deliveries from message_thread_id to direct_messages_topic_id. This silently broke forum-style topics in private chats (created via createForumTopic API), because Telegram accepts direct_messages_topic_id with ok: true but renders the message in General instead of the requested topic — no error, no retry, silent failure.

Full details in #55265.

Root Cause

There are two distinct private-chat topic topologies:

Topology	message_thread_id	direct_messages_topic_id	How created
Forum topics in private chat	✅ Works	❌ Silently ignored → General	createForumTopic API
Native DM-topics mode	✅ Works (after May 9 server fix)	✅ Works	Telegram client UI

The Bot API 10.0 regression (#22022) that originally broke message_thread_id was fixed by Telegram server-side on May 9, 2026. Both parameters now work for both topologies — except direct_messages_topic_id is silently ignored for forum topics.

cron/scheduler.py:1251-1266 could not distinguish between the topologies and used the parameter wrong for the more common case (forum topics).

Fix

Remove the is_private_dm_topic branch that set direct_messages_topic_id. Route through message_thread_id (the default path for all other targets). The adapter's existing thread-not-found fallback (plugins/platforms/telegram/adapter.py) already retries with direct_messages_topic_id if Telegram returns 400 thread not found — so native DM-topics mode is still covered.

Evidence

# message_thread_id → CORRECT (lands in topic)
sendMessage(chat_id=978174799, message_thread_id=252345)
→ ok: true, message_thread_id: 252345, is_topic_message: true

# direct_messages_topic_id → WRONG (silently ignored, lands in General)
sendMessage(chat_id=978174799, direct_messages_topic_id=252345)
→ ok: true, message_thread_id: null, is_topic_message: null  ← wrong location!

User confirmed via Telegram client: message_thread_id appears in the correct topic, direct_messages_topic_id appears in General.

Why not detect the topology?

getChat does not return is_forum: true for private chats with forum topics (the field is absent). There is no reliable Bot API to distinguish the two topologies at send time. Using message_thread_id first with a direct_messages_topic_id fallback is the robust approach — matching how the gateway adapter already works.

Testing

• Syntax: python3 -m py_compile cron/scheduler.py ✅
• Lint: no new errors introduced
• Live test: cron delivery to forum-topic private chat → message lands in correct topic
• Regression: cron delivery to native DM-topic private chat → thread-not-found fallback fires correctly

Related

• Closes [Bug] Cron delivery to private chat forum-topics lands in General — direct_messages_topic_id silently ignored (regression from #50023) #55265
• Supersedes the cron-path portion of fix(cron): route Telegram DM-topic cron delivery through DeliveryRouter (#22773) #50023
• Cron delivery to private DM topics broken after PR #22410 — send_message_tool.py missing three-mode routing #22773 (original issue), Telegram Bot API 10 breaks private chat topic replies; Hermes falls back to All Messages #22022 (Bot API 10.0 regression, fixed server-side)

[alt-glitch]

This was generated by AI during triage.

Competing fix with #52079 for the same bug (forum topics in private chats mis-routed to General via the cron is_private_dm_topic heuristic; tracked at #52060/#55265). This PR removes the heuristic branch and routes via message_thread_id, relying on the adapter's 400-thread-not-found fallback for native DM-topics mode. #52079 instead gates the DM-topic route on an explicit direct_messages_topic_id signal. Same code site, different mechanism — maintainer should pick one (#52079 is earlier and handles native DM-topics explicitly rather than via the retry fallback).

[tonydwb]

Code Review Summary

Verdict: LGTM

Fixes cron topic routing for private-chat forum topics. Uses message_thread_id directly instead of the overly-broad blanket switch from PR #50023.

• Clean simplification of topic routing logic
• Fixes regression from prior PR
• Well-scoped: 1 file, 28 additions

Reviewed 1 file, 28 additions. Approved.

[teknium1]

Thanks for the focused diagnosis. This is already fixed on current main by a stronger implementation. This is an automated hermes-sweeper review.

• Commit fc31f14cdaa1471181956d78bb9d7727bf22bde5 (fix(cron): disambiguate Telegram forum vs channel DM topics at delivery time (#52060)) shipped in v2026.7.7.
• cron/scheduler.py:1349 probes the live adapter and defaults private/forum targets safely to message_thread_id; only confirmed type == "channel" targets use direct_messages_topic_id.
• cron/scheduler.py:1645 applies that distinction consistently to both text and media delivery metadata.
• tests/cron/test_scheduler.py:3382 covers the reported forum-topic route, while tests/cron/test_scheduler.py:3628 preserves the channel DM-topic route.

This also addresses the member comment identifying the competing approaches: main retained the forum-topic fix while avoiding regression for genuine channel DM topics.