Margin

The alert

Four weeks before the close would have shown it

Monthly close is the wrong instrument for something that starts on a Tuesday and lives inside one segment. This lands the same week, with the cost line that moved first already isolated.

M
MarginAPP#eng-alerts
🔴 Contribution margin per order dropped −34.6%segment=resellers
Baseline
$18
Now
$12
Confidence
99.9%
Started
Aug 11
Book
unit economics (4 segments)
Segment
resellers
Break
Aug 10
Orders in window
374,400
Likely cause · Four cost-side metrics on the reseller segment break on the same day and no other segment moves. Shipping cost per order and support cost per customer rise together, which points at a mix change rather than a rate card change, and the refund rise arrives with them. Revenue kept growing through the whole window and blended gross margin moved under half a point, so nothing in the monthly review would have surfaced this.
  1. 1.Pull reseller orders since Aug 10 and check discount code usage against the partner allow list.
  2. 2.Break shipping cost per order by destination zone to confirm the mix shift.
  3. 3.Recompute reseller CAC payback with the new contribution margin before renewing the partner terms.
AcknowledgeFalse positiveCUSUM · q < 0.0001 · BH-corrected
M
MarginAPP#eng-alerts
🔴 Shipping cost per order jumped +49.4%segment=resellers
Baseline
$7.36
Now
$11
Confidence
99.9%
Started
Aug 10
Book
unit economics (4 segments)
Segment
resellers
Break
Aug 10
Orders in window
374,400
Likely cause · Four cost-side metrics on the reseller segment break on the same day and no other segment moves. Shipping cost per order and support cost per customer rise together, which points at a mix change rather than a rate card change, and the refund rise arrives with them. Revenue kept growing through the whole window and blended gross margin moved under half a point, so nothing in the monthly review would have surfaced this.
  1. 1.Pull reseller orders since Aug 10 and check discount code usage against the partner allow list.
  2. 2.Break shipping cost per order by destination zone to confirm the mix shift.
  3. 3.Recompute reseller CAC payback with the new contribution margin before renewing the partner terms.
AcknowledgeFalse positiveCUSUM · q < 0.0001 · BH-corrected
What this does not decide

This is a detector, not an accounting system. It does not restate your books, reallocate cost, or produce a number anyone should file. It reads the unit economics your finance team already computes and tells you the day one segment changed. Whether that changes a rate card, a partner agreement, or a spend decision is a call a human makes with the full context.