Every trading session knows its own risk. None of them knows what the others are doing. Three sessions sizing themselves independently against the same account are each perfectly reasonable on their own, and the aggregate is something nobody chose.

Where this fits

The last post was about the account — what it means when the balance isn't there yet, and the three production failures that came from treating a cached remote value as if the system owned it. This one is what the system does once it does know the balance: spend it deliberately, across every session at once.

Two earlier posts left this as a promise. The order-book post noted that portfolio_heat, portfolio_heat_warned, and portfolio_heat_blocked live in the trader's state but the calculation doesn't. The tick-to-trade post showed heat_blocked?/2 gating an order submission and deferred the aggregation behind it. This is that machine — the calculation, the thresholds, the rule that an exit always passes, and a recovery path that is only half built.