What happens when a connection drops
Two very different things can disconnect, and they have very different consequences. Your own device dropping costs you nothing. A broker session dropping is the case every copier has to be honest about. Here is exactly what MirrorFill does before, during, and after.
Your laptop or internet drops: nothing happens
The engine runs server-side. Your browser is a window onto it, not the thing doing the copying. Close the tab, lose your Wi-Fi, shut the laptop: copying continues untouched. When you sign back in, the Trade Desk shows you what happened while you were away.
A broker session drops: the recovery sequence
- Auto-reconnect with backoff. For an ordinary drop, the engine notices and retries, spacing attempts out so it does not hammer a gateway that is already struggling. The topbar pill shows Reconnecting, and the alerts bell records the event, with a toast reading "Connection lost. Reconnecting...". Positions are untouched. (One drop is deliberately never retried, see below.)
- Re-read positions from the broker. On reconnect, the engine re-reads every account's live position from the broker rather than trusting what it last saw. While you were down, a resting order may have filled; asking the broker is the only honest source.
- Resubscribe and reconcile. It resubscribes to fills, then compares what each follower holds against what it should hold and corrects the difference. See how drift gets fixed.
No double-sends on the way back: the engine acts on each fill id exactly once, so replayed events after a reconnect cannot duplicate an order.
The one drop we do not retry
If the broker reports the session was taken over by the same login connecting somewhere else (Rithmic's forced logout, or Volumetrica logging the copier off for a concurrent session), reconnecting would force that other session out, it would reconnect and force ours out, and the two apps would ping-pong the login until the broker disables it. So for this one drop the copier stops instead of retrying: the engine strip shows Stopped with an amber dot instead of the neutral idle one, the reason is spelled out in a toast that stays on screen until you dismiss it and in the alerts bell afterwards, an e-mail goes out immediately if alerts are on, and nothing reconnects until you close the other session and press Start copying yourself. Positions are untouched, as with any stop. See Rithmic session conflicts.
The disconnect alert
A dropped broker session raises an in-app toast immediately, and, if alerts are on, an e-mail after a short debounce.
The debounce is the interesting part. The reconnect backoff runs up to 30 seconds, so a session that drops and comes straight back is routine; mailing about it would train you to ignore the alert that matters. The e-mail waits out a window (45 seconds by default, set by the operator), and if the connection returns inside it, nothing is sent at all. If the loss was reported, the recovery is reported too, under the same switch, so you never get half the story.
The forced-logout alert is the exception: it is not debounced, because nothing will reconnect on its own: waiting would only delay the news that copying stopped.
The honest limit
No copier can place orders while a broker session is down. Not this one, not any other. If the leader fills during the outage, the follower cannot mirror it until the session is back. What a copier can control is the recovery: notice fast, retry sensibly (and know when retrying would make things worse, as after a forced logout), rebuild from the broker's book instead of a stale guess, and correct the gap the moment it can. That is the part MirrorFill engineers for.
Your open positions are unaffected by the outage itself: they live at the broker, not in the copier. A disconnect never closes anything.
Quick answers
My browser crashed mid-trade. Did copying stop?
No. The engine runs on the server, not in your browser. Sign back in and check the Trade Desk. Everything kept running.
Does a broker disconnect close my positions?
No. Positions live at the broker and stay exactly as the broker holds them. The copier reconnects, re-reads them, and reconciles.
What if the leader filled while a follower's session was down?
The mirror could not be placed during the outage. After reconnect, reconciliation sees the follower is behind and corrects the difference, visibly, in Order history.
Why didn't the copier reconnect this time?
Open the alerts bell, or read the toast if it is still on screen. If it says the login was signed in somewhere else, the broker forced the session out because the same login connected elsewhere. The strip itself only says Stopped, with an amber dot rather than the neutral idle one; the reason lives in the bell. Reconnecting would fight that session for the login, so the copier stops instead. Close the other app, then press Start copying. See Rithmic session conflicts.