When a non-default accountId is specified but not found in the accounts
config, resolveTelegramToken() falls through to channel-level defaults
(botToken, tokenFile, env) — silently routing messages via the wrong
bot's token. This is a cross-bot message leak with no error or warning.
Root cause: extensions/telegram/src/token.ts:44-46, resolveAccountCfg()
returns undefined for unknown accountIds but code continues to fallbacks.
Introduced in e5bca0832f when Telegram moved to extensions/.
Fix: return { token: "", source: "none" } with a diagnostic log when
a non-default accountId is not found. Existing behavior for known
accounts (with or without per-account tokens) preserved.
Test: added "does not fall through when non-default accountId not in
config" — 1/1 new, 10/10 existing unaffected.
Closes#49383
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: HCL <chenglunhu@gmail.com>
