Magic numbers and running several EAs on one account

2 October 2026 · Soft Trade Enterprises · All guides

What a magic number is

An integer you attach to every order your EA sends. The server stores it with the resulting position, and it is the only reliable way for an EA to tell "my position" from "someone else's position" — whether that someone is another EA or you, trading by hand.

MqlTradeRequest request = {};
request.magic  = MagicNumber;     // stamped on the order
request.symbol = _Symbol;
request.volume = lots;
// ...

The failure it prevents

An EA with no magic filter loops over every open position and manages all of them. Attach two such EAs and the first one trails the stop on the second one's trade, then closes it on its own exit condition. Add a manual trade and it gets managed too.

Nothing errors. The log looks normal. You only notice from the account history, usually after a few days.

Filter on magic and symbol, both

int CountMyPositions()
{
   int n = 0;
   for(int i = PositionsTotal()-1; i >= 0; i--)
   {
      ulong ticket = PositionGetTicket(i);
      if(ticket == 0) continue;
      if(PositionGetInteger(POSITION_MAGIC) != MagicNumber) continue;
      if(PositionGetString(POSITION_SYMBOL)  != _Symbol)     continue;
      n++;
   }
   return n;
}

Magic alone is not enough once the same EA runs on several charts. Two instances sharing a magic number will each think the other's positions are their own.

A scheme that survives growth

Pick a structure before you need one, because renumbering later means reconciling live positions:

Digits	Meaning	Example
1–2	Strategy ID	12 = your breakout EA
3–4	Symbol ID	01 = XAUUSD
5–6	Timeframe ID	15 = M15

So 120115 is "breakout EA, XAUUSD, M15". Readable in the terminal at a glance, and it never collides.

Two things to avoid: do not generate magic numbers randomly at startup, because after a restart the EA no longer recognises its own positions; and do not derive them from the symbol name at runtime unless the derivation is stable, because a broker suffix change will silently produce a different number.

Margin is shared even when positions are not

Magic numbers isolate ownership. They do not isolate margin. Every EA on the account draws on the same free margin, so three EAs each sized "safely" on their own can combine into something that is not.

If you run several, one of them should hold an account-level ceiling — total exposure across all magics, not just its own:

double TotalLots()   // every position, every magic
{
   double v = 0.0;
   for(int i = PositionsTotal()-1; i >= 0; i--)
      if(PositionGetTicket(i) > 0)
         v += PositionGetDouble(POSITION_VOLUME);
   return v;
}

And remember the account-level stop: margin level, daily drawdown or equity floor apply to the whole account regardless of which EA caused them.

Practical rules for multi-EA accounts

• One magic number per EA per symbol per timeframe
• Make it an input, so it can be changed without recompiling
• Print it in OnInit() so the Experts log says what is running where
• Keep a written list of which magic belongs to which chart
• Agree an account-wide exposure ceiling and give exactly one EA the authority to enforce it
• Test by running two instances on demo and confirming neither touches the other's positions

If you are commissioning several EAs over time, tell each developer the scheme. Two builds that both default to 12345 is the most common collision we are asked to untangle.