Loop prevention: why an account cannot be a follower

This article explains why Replikanto sometimes refuses to turn on an account as a follower and shows the message "Account '...' cannot be a follower to prevent trade in looping", what a copy loop is, why a follower can be left turned off after you update to Replikanto 1.7.0.0, and how to fix your setup.

What a copy loop is

A copy loop happens when trades travel through other Replikanto tabs back to the account they started on. Every copy then produces another copy, so the same trade keeps coming back.

The simplest example uses two tabs:

Tab 1: leader account A, follower account B.
Tab 2: leader account B, follower account A.

A trade placed on A is copied to B by Tab 1. Tab 2 sees that trade on B and copies it back to A, and so on. The same can happen across three or more tabs (A to B, B to C, C back to A), and with Cross Order changing the instrument between tabs (for example ES in one tab and MES in another).

The check follows the instrument: another tab only counts as part of the chain when its leader trades the instrument the copy arrives on. A chain that never comes back to an account already in it (A to B, then B to C) is not a loop and is allowed.

The messages you may see

When you turn a follower on

If checking an account as a follower would close a loop, Replikanto shows a warning window:

Account '...' cannot be a follower to prevent trade in looping

The account is left turned off (Off) in the follower list. The NinjaTrader Log tab shows:

Replikanto: [Follower] This account cannot be checked as a follower because it is already the leader of another Replikanto tab; allowing it would copy trades in a loop. account='...'

Replikanto runs this check when you check a follower, when you change a follower's Cross Order instrument, when a tab opens with the workspace (every follower of the tab is checked again) and when you import a follower list. On an import, only the Log line is shown, without the window.

While copying a trade

As a second safety net, Replikanto also checks each copy just before sending it. If a follower account was about to copy a trade back to its own leader, the copy is not sent and the Log shows this alert:

Replikanto stopped a copy loop: a follower account was about to copy a trade back to its own leader. Check your configuration, or contact FlowBots support.

Versions before 1.7.0.0 showed the same alert as "Replikanto loop prevention performed! Check your configuration or contact FlowBots support."

What changed in Replikanto 1.7.0.0

Starting with Replikanto 1.7.0.0, loop prevention also catches loops that it used to miss:

a loop that went through a tab reopened with the workspace;
a loop across three or more tabs with Cross Order changing the instrument between them.

After updating, this is expected: if your saved workspace already contained one of these loops, the first time you open it with 1.7.0.0 Replikanto shows the "cannot be a follower to prevent trade in looping" warning and leaves that follower turned off. Nothing is wrong with the update. Your setup had a loop, and it is now blocked before it can copy trades in circles.

How to fix it

Decide which account should lead. An account can receive a trade or pass it on, but a trade must never come back to the account it started on.
Find the tabs involved. Look at the leader account and the followers of each tab (in every Replikanto window) for the account named in the message.
Remove the account from one of the tabs: uncheck it as a follower in the tab where it closes the circle, or choose a different leader in that tab.
Check the follower list of each tab again. The warning should no longer appear when you turn the remaining followers on.

If the Log shows "The cross-tab loop-prevention check failed and allowed this follower without completing its scan; verify manually...", Replikanto could not finish the check and turned the follower on anyway. Check by hand, as in the steps above, that this follower does not close a loop.

Limits of loop prevention

Same NinjaTrader only. The check covers every Replikanto window and tab in the same NinjaTrader. It does not follow trades sent to another machine over the local network or the internet.
Inactive workspaces. A tab in another, inactive NinjaTrader workspace is left out of the check only when both tabs have Prevent copying in an inactive workspace turned on (right-click the Replikanto window > Properties... > General). If either tab has it turned off, that tab counts.
Between machines. To stop remote followers from sending your trades on to other accounts, the leader can turn on Block copying of submitted trades (Properties > General).