X0508 4 2026-02-19 0 0001918102 DEEP FISSION, INC. NONE 0002110467 Peres Mark Wayne C/O DEEP FISSION, INC. 2001 ADDISON STREET, SUITE 300 BERKELEY CA 94704 0 1 0 0 Chief Nuclear Officer 0 Restricted Stock Unit 0 2026-02-19 4 A 0 25000 0 A 2033-02-19 Common Stock 25000 25000 D Employee Stock Option (right to buy) 15.00 2026-02-19 4 A 0 15000 0 A 2027-02-19 2036-02-19 Common Stock 15000 15000 D 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. 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. /s/ Jon Gordon as attorney-in-Fact for Mark Peres 2026-02-23