Elizabeth Muller - 05 Sep 2025 Form 4 Insider Report for DEEP FISSION, INC.

Role: President and Chief Executive, Director
Signature: /s/ Elizabeth Muller
Issuer symbol: N/A
Transactions as of: 05 Sep 2025
Net transactions value: $0
Form type: 4
Filing time: 09 Sep 2025, 17:16:33 UTC
Previous filing: 18 Aug 2025
Next filing: 07 Oct 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	09 Sep 2025	0002081850

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction		Common Stock	Award		+5,196,426			5,196,426	05 Sep 2025	Direct	F1
transaction		Common Stock	Award		+5,057,855			5,057,855	05 Sep 2025	By Muller Family Trust	F1, F2

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

Explanation of Responses:

Id	Content
F1	Received in connection with the Issuer's merger (the "Merger") with Deep Fission Inc. ("Legacy Deep Fission") in accordance with 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 Legacy Deep Fission (the "Merger Agreement"), in exchange for shares of Legacy Deep Fission common stock. Pursuant to the terms of the Merger Agreement, at the effective time of the Merger, each issued and outstanding share of Legacy Deep Fission common stock was converted into the right to receive 17.32142 shares of the Issuer's common stock, rounded to the nearest whole share.
F2	Ms. Muller controls the right to vote and dispose of the shares held by the Muller Family Trust (the "Trust") and accordingly, may be deemed to beneficially own the shares held by the Trust. Ms. Muller expressly disclaims beneficial ownership of all securities held by the Trust except to the extent of her pecuniary interest therein.

Content

Received in connection with the Issuer's merger (the "Merger") with Deep Fission Inc. ("Legacy Deep Fission") in accordance with 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 Legacy Deep Fission (the "Merger Agreement"), in exchange for shares of Legacy Deep Fission common stock. Pursuant to the terms of the Merger Agreement, at the effective time of the Merger, each issued and outstanding share of Legacy Deep Fission common stock was converted into the right to receive 17.32142 shares of the Issuer's common stock, rounded to the nearest whole share.

Ms. Muller controls the right to vote and dispose of the shares held by the Muller Family Trust (the "Trust") and accordingly, may be deemed to beneficially own the shares held by the Trust. Ms. Muller expressly disclaims beneficial ownership of all securities held by the Trust except to the extent of her pecuniary interest therein.