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

Reporting relationship: President and Chief Executive, Director
Issuer ticker: FISN on Nasdaq
Reported as of: 05 Sep 2025
Net transaction value: $0
SEC form: 4
Accepted by SEC: 09 Sep 2025, 17:16:33 UTC
Prior SEC filing: 18 Aug 2025
Next SEC filing: 07 Oct 2025
Source filing: View source filing
Reporting owner signature: /s/ Elizabeth Muller

Key filing fact

Elizabeth Muller filed Form 4 for DEEP FISSION, INC. on 09 Sep 2025.

Key facts

This page summarizes Elizabeth Muller's Form 4 filing for DEEP FISSION, INC..
2 reported transactions and 0 derivative rows are listed below.
Accepted by SEC: 09 Sep 2025, 17:16.

Change

Previous filing in this sequence was filed on 18 Aug 2025.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0002081850 Primary reporting owner

Muller Elizabeth

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

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

No ticker transaction

Common Stock

Award

Transaction value
Shares: +5,196,426
Change %
Price
Shares after: 5,196,426
Date: 05 Sep 2025
Ownership: Direct
Footnotes: F1

No ticker transaction

Common Stock

Award

Transaction value
Shares: +5,057,855
Change %
Price
Shares after: 5,057,855
Date: 05 Sep 2025
Ownership: By Muller Family Trust
Footnotes: F1, F2

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 2 footnotes

Footnote 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.

Footnote 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.