Live regression (Alice, 2026-08-19): a continuable cron with
cron_continuable_surface=in_channel delivered its brief flat, but the
flat-session seed was gated on mirror_this_target = mirror_enabled AND
origin-match. Without attach_to_session (and with cron.mirror_delivery
defaulting False) the seed never ran; the next plain reply resolved to a
blank (slack, chat, None) session and the agent had no idea about its own
delivery message — not continuable in channel OR thread (in_channel mode
correctly skips thread creation, so there was no thread session either).
in_channel IS the continuation surface, not a mirror nicety: gate the seed
on origin-match alone, and resolve origin_user_id for any origin-matching
target so the seeded key still carries the scheduling user on
per-user-isolated chats. attach_to_session remains the opt-in for the
separate default-surface mirror behavior.
Regression test drives the delivery path with attach_to_session=False and
asserts the seed fires with the right user_id (fails on pre-fix code).
Victor Kyriazakos
3c52d3589f