Since 5ea8fb2b78 (#111624, for #110952) the gateway rejects a bare silence
marker on any human turn and delivers "The model returned only a silence
marker for a message that needed a reply" instead. That protects a human
who asked this bot something and got nothing back. It also fires on every
human message the adapter admitted without the bot being addressed at all:
a free-response channel, a thread follow-up under
`thread_require_mention: false`, or a message @-mentioning another person
or bot with `ignore_other_user_mentions: false`. A bot whose SOUL declines
peer-addressed turns with a deliberate marker now posts that notice on
every such message. A fleet running several bots in shared Slack threads
reported it as spam on v2026.9.21. #37940 established that intentional
silence must not be re-inflated. Both contracts hold once the turn knows
whether a reply was expected.
`MessageEvent.reply_expected` (True, False, None) is set by the adapter
where the message is admitted. Slack (`slack_reply_expected`): a 1:1 DM,
an @mention of this bot or a command is True, anything else it admits is
False. Other adapters leave None, which keeps today's behaviour, so nothing
changes for them until they are ported. `response_filters.silence_allowed`
holds the one rule (machinery turn, or reply not expected) and both call
sites use it: the live turn in `run_turn._hmwa_shape_agent_response` and
the crash-recovery redelivery from #120377 (1136f135dd), which reads the
flag back from the persisted turn metadata. The suppressed case logs one
DEBUG line naming platform and chat.
Operator workaround until this lands: `platforms.slack.extra.
ignore_other_user_mentions: true` drops peer-addressed messages before a
turn exists.
(cherry picked from commit 094439776ab898cccde303a1c2c911c8ab5bfb75)
b08bb5afb8