Getting started · updated 2026 · ~4 minute read

Known limitations

Every tool has edges. Here are ours, and where a limit is a design decision, we say why. If something on this page is a dealbreaker for you, better to know now.

Execution

Unfilled quantity is written off, never chased. With order expiry on, a follower order that hasn't filled after your N seconds is cancelled and the missed quantity is written off. We deliberately never re-send it at market: by the time an order has sat unfilled through your expiry window, the price has moved, and chasing it converts a missed fill into a bad one. The written-off amount clears when the leader goes flat or reverses.

No synthetic stop or target brackets. Followers mirror the leader's own exits, delta-exact: when your stop or target fills on the leader, every follower closes with it. MirrorFill does not attach brackets of its own on top. Two bracket systems working the same position can disagree, and a copier that quietly manages exits you didn't place is a copier you can't reason about. How this plays out in practice: how exits copy.

Platform coverage

Futures only. MirrorFill runs on a fixed registry of CME, CBOT, NYMEX, and COMEX instruments with known tick sizes. No equities, no spot FX.

Supported platforms are Rithmic, Tradovate, and Volumetrica (dxFeed). There is no NinjaTrader, TradingView, or MetaTrader 4/5 support. Topstep's TopstepX / ProjectX platform is not supported. If your accounts live there, MirrorFill can't copy them today, and we'd rather say so plainly than let you find out after signing up.

One Tradovate session per login. Tradovate allows a single active session per login, so running the copier and another tool on the same credentials can conflict. If your followers are on Tradovate, see Tradovate session conflicts.

One Rithmic session per login. Rithmic forces the oldest session out when the same login connects again. If that happens to the copier (you sign into R|Trader or your firm's platform on the login the copier is using), the copier stops and stays stopped rather than fight for the login, and tells you why. See Rithmic session conflicts.

While the copier runs

The copier holds live broker sessions the whole time. From Start to Stop, MirrorFill keeps a persistent connection open per broker login (on Rithmic, one session per plant). That is what mirrors fills in real time, and it is the session another sign-in on the same login would force out.

Copy rules are read-only while the engine is running. Structural changes (adding a follower, changing the leader, changing sizing) require a stop first. This is deliberate: the engine's routing is fixed while live, so an edit can never land halfway through a fill. The per-follower Follow switches still work mid-session, so pausing one account never requires a stop. Details: editing rules while the copier runs.

Alerts and billing

Alerts cannot tell you the app is down. Risk limits and alerts are enforced and sent by the running copier, so nothing fires and nothing is delivered while the app is not running, and silence is not proof that nothing happened. An external uptime check on the site is the only thing that can report the app itself being unavailable. Seven engine events are e-mailed (risk breach, the 80% warning, lockout, copier stopped, connection lost, forced logout, order written off), with per-event switches in Settings; copy-execution failures remain in-app only.

Monthly billing only. There is no annual plan. Plans are on the pricing page.

Speed

We publish no latency number. We haven't measured copy latency under production load, so quoting one would be a guess dressed as a benchmark. What we can say: copying is triggered by fills and happens in real time, as fills happen. If we publish a figure one day, it will come with the methodology.

Quick answers