Mark Wayne Peres - 19 Feb 2026 Form 4 Insider Report for DEEP FISSION, INC.

Reporting relationship: Chief Nuclear Officer
Issuer ticker: FISN on Nasdaq
Reported as of: 19 Feb 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 23 Feb 2026, 21:10:58 UTC
Next SEC filing: 10 Mar 2026
Source filing: View source filing
Reporting owner signature: /s/ Jon Gordon as attorney-in-Fact for Mark Peres

Key filing fact

Mark Wayne Peres filed Form 4 for DEEP FISSION, INC. on 23 Feb 2026.

Key facts

This page summarizes Mark Wayne Peres's Form 4 filing for DEEP FISSION, INC..
2 reported transactions and 2 derivative rows are listed below.
Accepted by SEC: 23 Feb 2026, 21:10.

Change

No earlier filing in this sequence is available for direct comparison.
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 0002110467 Primary reporting owner

Peres Mark Wayne

Relationship: Chief Nuclear Officer
Address: C/O DEEP FISSION, INC., 2001 ADDISON STREET, SUITE 300, BERKELEY
Signature: /s/ Jon Gordon as attorney-in-Fact for Mark Peres
Signature date: 23 Feb 2026

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

No ticker transaction Derivative

Restricted Stock Unit

Award

Transaction value: $0
Shares: +25,000
Change %
Price: $0.000000
Shares after: 25,000
Date: 19 Feb 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 25,000
Exercise price: $0.000000
Footnotes: F1

No ticker transaction Derivative

Employee Stock Option (right to buy)

Award

Transaction value: $0
Shares: +15,000
Change %
Price: $0.000000
Shares after: 15,000
Date: 19 Feb 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 15,000
Exercise price: $15.00
Footnotes: 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

Each RSU vests based on attainment of both a service-based vesting condition and liquidity event vesting condition, in each case, prior to the expiration date. 25% of the service-based vesting condition will be satisfied on the one-year anniversary of the grant date and the remainder in equal monthly installments thereafter, subject to the reporting person's continued service through the vesting dates. The liquidity event condition will be satisfied on the earliest to occur of a change in control, initial public offering or direct listing.

Footnote F2

Date at which first vesting occurs is indicated. One-fourth of the total number of options to purchase the Company's common stock vests on the first vesting date shown and an additional one-thirty sixth on each month thereafter until fully vested.