Live-canary finding #3 (Alice, staging): the relay inbound leg is
at-least-once. On WS re-handshake the connector replays its durable
per-instance buffer; a long multi-tool turn (60-100s) straddling a quiet
socket drop got its ORIGINAL inbound replayed after the turn finished,
re-running the entire turn — the user saw the final answer posted 2-5x
(each a separate execution, hence slightly different texts). Receipts:
same msg text at history=0 in back-to-back sessions 121647/121840, no
Slack-side retry on the connector (envelope dedupe never fired).
Consumer-side idempotency: bounded FIFO seen-set (512) keyed by platform
message identity; events without a message_id never dedupe (fail-open —
dropping a real message is worse than rerunning one). No wire change;
contract v1 untouched.
Transplanted-from: victor-fork/feat/relay-slack-live-cards@73ce04ae75 (extracted for the rc.4 relay-fixes train; tests moved to a standalone file with no live-cards dependencies)
Victor Kyriazakos
b5f95d0890