Two follow-ups from a contour test where a user joined the chat, then
registered, and got no write access — with silent logs.
Observability: log every chat_member update (chat id, configured id, user,
old->new status), the eligibility result and the grant outcome; plus a startup
self-check that warns loudly when the bot is not an administrator in the chat
with the restrict-members ("Ban users") right — the common misconfiguration,
previously invisible in the logs.
Grant on first registration: a user who joins the moderated chat BEFORE
registering is covered by no chat_member event, so the join-time grant never
fires for them. ProvisionTelegram now reports first contact, and the Telegram
auth handler emits chat_access_changed on it, so the gateway re-evaluates and
grants write access if the user is already in the chat.
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