Done. The forecast change note is written to `output/drivers-note.md`. 

**EBITDA fell ($149K) or 32.9%** from Prior to Current. The three drivers that moved:

1. **Active customers** (46 → 44): Lost 2 customers all year, cutting EBITDA by ($133K) — the largest negative impact.
2. **Gross margin** (26.2% → 26.6%): Expanded by 40bp year-round, adding $39K to partially offset the customer loss.
3. **Headcount** (23.00 → 23.75 FTE): Added 0.75 FTE over 9 months, costing ($54K) in additional opex.

The note asks which documented assumptions support each change. The customer loss and headcount increase together account for ($187K) of the EBITDA decline, while margin improvement partially offsets to net ($149K) down.