The promo message body now renders "@<bot>" as an HTML text_link to the same ?startapp deep link the button uses (ParseMode HTML), so tapping the mention opens the seeded Mini App instead of the bot profile. Same payload (campaign start-param, else the forwarded /start payload) backs both the button and the mention.
The main bot is now an admin in the moderated discussion group and receives its
messages (allowed_updates includes message). Its default handler replied to
every message with a Mini App launch button — an inline web_app button, which
Telegram permits only in private chats — so replying in the group failed with
BUTTON_TYPE_INVALID (silently: the send fails, no user-facing error). Reply only
in a private chat; in the group the bot only manages permissions. The promo bot
gets the same guard.
Add a second standalone promo bot to the bot container (answers /start with a
localized message + a URL button into the main bot's Mini App) and gate write
access in a channel's linked discussion chat: grant on join when the Telegram
user is registered and neither admin-suspended nor holding a new chat_muted
role, and revoke/grant on the matching moderation change for a member currently
in the chat.
Eligibility (registered AND NOT suspended AND NOT chat_muted; the game
suspension dominates) is resolved once in the backend and reached two ways: the
bot's join-time unary ResolveChatEligibility over the existing mTLS bot-link,
and a backend chat_access_changed event -> gateway -> ChatGate command
(idempotent; a temporary-block-expiry sweeper may over-emit). The bot guards the
block/unblock path with getChatMember, since bots cannot list members.
A web_app button cannot open another bot's Mini App (it signs initData with the
sending bot's token), so the promo button is a t.me ?startapp URL reusing the
UI's VITE_TELEGRAM_LINK. The bot must be a chat admin with the restrict-members
right and chat_member in its allowed updates.
No schema change: chat_muted reuses the data-driven account_roles table.
Ilia Denisov