Telegram intersects the chat default with each user's permissions, so a per-user
grant can never exceed a deny-by-default group: the original default-deny +
grant design could not let any user write (can_send=true was AND-ed with the
denying default). Invert it — the chat allows sending by default and the bot
MUTES an ineligible member (unregistered, admin-suspended, or chat_muted) and
restores an eligible one it had muted, acting only when the current state
differs (idempotent, no self-loop). The block/unblock/chat_muted/registration
path already sets can_send to the eligibility, so it is unchanged.
The CanSendMessages loop-guard skipped exactly the stuck case — a restricted
member whose chat_member event reports can_send=true yet who cannot actually
write. Replace it with a precise loop guard (skip only the bot's own restrict
action, i.e. the update whose performer is the bot) and grant any eligible
in-chat member (member or restricted) otherwise. Also log the new member's
can_send, is_member and the actor id for full visibility.
A default-deny discussion group reports a present or freshly joined member as
`restricted` (no send right), not `member`. The join filter required `member`,
so the real case never matched and a registered user stayed muted. Grant any
eligible in-chat member (member or restricted) that still lacks the send right,
with a loop guard (skip when send is already allowed) so the bot's own grant
does not re-fire. Revoking a now-ineligible user stays the chat-gate path's job,
so this never fights a chat_muted/block.
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