Margin headroom as a risk number in its own right

Module 3 budgeted tonight's flow. This lesson promotes the arithmetic to what the seed called it: a risk number in its own right, with a floor, checked before every entry.

The metric

Headroom in days: free cash above initial margin, divided by the book's plausible one-day adverse flow - per-point values times plausible ranges, summed with lesson 7's correlation honesty. £8,000 of headroom against £1,600 of plausible daily flow is 5 days of ordinary adversity the account can absorb before the machinery starts making its own decisions. The floor is the plan's: enough days that a bad week is bookkeeping, scheduled events counted at their multiples, and the number recomputed whenever the book or the regime changes.

Why days, and why a floor

• Days are the honest unit: cash amounts flatter and percentages obscure - 'how many ordinary bad days until forced decisions' is the question the metric answers directly.
• The floor refuses entries: a new position's variation flow shrinks the days - an entry that takes the book below floor is refused on headroom exactly as an oversized one is refused on budget: two gates, equal rank.
• The metric is leading, not lagging: margin calls are the machinery noticing headroom exhausted - the floor is the same information, read before the position exists instead of after.

The two-gate discipline

Futures sizing now runs two checks where other tracks ran one: the budget gate - risk per trade against the stop - and the headroom gate - the book's days against the floor. They bind differently: the budget gates each trade's loss; the headroom gates the book's capacity to hold all its trades through ordinary variance. A book can pass every budget check and still sit two bad days from forced selling - which is exactly the account the seed's phrase was written about, and exactly what the second gate exists to refuse.