Three symbols can still be one risk

Counting open positions can create a false sense of diversification. Different symbols may share a currency, sector, macro driver or directional exposure. When that driver moves, several positions can react together. The labels are different; the risk may not be.

Correlation is not fixed. It changes with the time window, market regime and event being studied. A relationship visible over one period may weaken or reverse in another. That is why a correlation number should support a review, not become a permanent assumption about two assets.

Map the common driver

For each open position, note the broad factor that could make the thesis fail: a quote currency, equity beta, rates sensitivity, commodity input or a shared technical condition. Then ask what the portfolio would look like if that factor moved against all of them. This is a scenario question, not a forecast.

Aggregate risk before adding a position. Include intended loss at invalidation, not just notional value, and account for the fact that stops may not execute at the requested price during a gap. If the combined exposure is difficult to explain in one sentence, it deserves a slower review.

Controls and judgement

A maximum open-position count is useful, but it cannot identify every shared driver. A symbol allowlist, exposure group or aggregate risk ceiling can add structure, while still requiring judgement about what the groups mean. Document the rule and review it when the portfolio or market changes.

Diversification is not the same as safety, and a correlation estimate is not a trade signal. The useful outcome is a clearer picture of what could move together and a deliberate decision about whether that exposure fits your limits.