Carry forward focused follow-ups from PR #45741: treat PTB's raw Bot API 10.1 response shapes safely, recognize real missing-endpoint errors, preserve link preview settings on rich sends, and lock the rich limit to Telegram's character-based cap.
Remove the rich_messages config toggle entirely so Telegram replies always try the Bot API 10.1 rich-message path first, with the existing MarkdownV2 fallback/latch behavior for unsupported endpoints and per-message failures.
Restore the Telegram platform hint to encourage rich Markdown tables/task lists/math now that the rich path is the default, and remove the config/docs surface for the old toggle.
- Use reply_parameters per the sendRichMessage spec instead of the
undocumented reply_to_message_id scalar (silently ignored -> reply
anchor quietly dropped).
- Latch rich sends off after an endpoint-capability failure (old PTB /
server without sendRichMessage) so every later reply doesn't pay a
doomed extra roundtrip; per-message BadRequests do NOT latch.
- Default rich_messages to OFF (opt-in) while the day-old Bot API 10.1
endpoint is validated live; revert the prompt-hint table guidance
until the default flips on.
- Tests: reply_parameters shape, send-latch behavior, BadRequest
non-latch; rich tests opt in explicitly via extra.
Introduce opportunistic support for Telegram Bot API 10.1 rich messages by sending raw agent Markdown via sendRichMessage and streaming previews via sendRichMessageDraft. Implements a rich-path fast‑path in gateway/platforms/telegram.py (RICH_MESSAGE_MAX_BYTES=32768, feature gate platforms.telegram.extra.rich_messages, bot capability checks, routing/thread handling, and conservative fallback rules: permanent/capability errors fall back to the legacy MarkdownV2 path, transient/network errors are surfaced without legacy-resend). Also add a latch for draft capability failures (_rich_draft_disabled) and preserve legacy chunking and draft behavior when needed. Update agent prompt hints (telegram encourages rich Markdown/tables), add CLI config example option, update English and Chinese docs to describe rich messages and fallbacks, and add/adjust tests for rich send and draft behavior.
Justin Sunseri