Form 4 Filing for BillionToOne, Inc.

This filing details stock transactions by John Roderick ten Bosch, SVP of Laboratory Operations at BillionToOne, Inc. On October 5, 2026, ten Bosch sold 1417 shares of Class A Common Stock at a price of $105.15 per share, under a Rule 10b5-1 trading plan. This transaction was executed twice, resulting in post-transaction holdings of 20802 shares and 19385 shares respectively. The transactions were marked as direct ownership. The filing was made on October 7, 2026.