Elizabeth Muller - Sep 5, 2025 Form 3 Insider Report for DEEP FISSION, INC.

Role: President and Chief Executive, Director
Signature: /s/ Elizabeth Muller
Transactions as of: Sep 5, 2025
Transactions value $: $0
Form type: 3
Date filed: 9/9/2025, 05:14 PM
Previous filing: Aug 18, 2025
Next filing: Oct 7, 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Muller Elizabeth	President and Chief Executive, Director	C/O DEEP FISSION, INC., 2831 GARBER STREET, BERKELEY	/s/ Elizabeth Muller	2025-09-09	0002081850

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		Employee Stock Option (right to buy)							Sep 5, 2025	Common Stock	812K	$51.20	Direct	F1, F2

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

Explanation of Responses:

Id	Content
F1	Received pursuant to the terms of the Agreement and Plan of Merger and Reorganization dated as of September 5, 2025, by and among the Issuer (f/k/a Surfside Acquisition Inc.), Deep Fission Acquisition Co. and Deep Fission Inc. ("Legacy DF") in exchange for options to acquire shares of Legacy DF common stock. The number of shares of Legacy DF common stock subject to such options (the "option shares") was converted into an option to purchase the number of shares of the Issuer's common stock equal to the option shares multiplied by 17.32142 (the "Conversion Ratio"), rounded down to the nearest whole share, and the exercise price of each option was divided by the Conversion Ratio, rounded up to the nearest whole cent. The options were acquired by the Reporting Person prior to the Reporting Person becoming an executive officer of the Issuer. The Reporting Person was appointed as a director and executive officer of the Issuer effective immediately after the effective time of the Merger.
F2	The shares subject to this option vest over a 4-year period, with 25% of the underlying shares vesting on June 1, 2025 and 1/48th of the shares underlying shares vesting monthly over the 36-month period thereafter, subject to the executive's continued employment through each vesting date.

Content

Received pursuant to the terms of the Agreement and Plan of Merger and Reorganization dated as of September 5, 2025, by and among the Issuer (f/k/a Surfside Acquisition Inc.), Deep Fission Acquisition Co. and Deep Fission Inc. ("Legacy DF") in exchange for options to acquire shares of Legacy DF common stock. The number of shares of Legacy DF common stock subject to such options (the "option shares") was converted into an option to purchase the number of shares of the Issuer's common stock equal to the option shares multiplied by 17.32142 (the "Conversion Ratio"), rounded down to the nearest whole share, and the exercise price of each option was divided by the Conversion Ratio, rounded up to the nearest whole cent. The options were acquired by the Reporting Person prior to the Reporting Person becoming an executive officer of the Issuer. The Reporting Person was appointed as a director and executive officer of the Issuer effective immediately after the effective time of the Merger.

The shares subject to this option vest over a 4-year period, with 25% of the underlying shares vesting on June 1, 2025 and 1/48th of the shares underlying shares vesting monthly over the 36-month period thereafter, subject to the executive's continued employment through each vesting date.