John Lister - 05 Nov 2025 Form 3 Insider Report for BillionToOne, Inc.

Role: Chief Administrative Officer
Signature: /s/ Thomas P. Lynch, Attorney-in-Fact
Issuer symbol: BLLN on Nasdaq
Transactions as of: 05 Nov 2025
Net transactions value: $0
Form type: 3
Filing time: 05 Nov 2025, 21:30:44 UTC
Next filing: 12 Nov 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
LISTER JOHN	Chief Administrative Officer	C/O BILLIONTOONE, INC., 1035 O'BRIEN DRIVE, MENLO PARK	/s/ Thomas P. Lynch, Attorney-in-Fact	05 Nov 2025	0001464741

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
holding	BLLN	Stock Option (right to buy)							05 Nov 2025	Common Stock	133,300	$23.15	Direct	F1, F2

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	The options are subject to a service-based vesting requirement, which shall be satisfied over a four-year period, with 25% of the options vesting on July 7, 2026. The remaining 75%. vest and become exercisable in equal monthly installments over the following three years, subject to the Reporting Person's continuous service with the Issuer through each such vesting date.
F2	Immediately prior to the completion of the Issuer's initial public offering of Class A common stock, each share of Common Stock shall be reclassified into one share of Class A Common Stock.

Remarks:

Exhibit 24 - Power of Attorney