UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): February 1827, 2026

Deep Fission, Inc.

(Exact name of registrant as specified in its charter)

Delaware	000-56407	87-4265302
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification No.)

2001 Addison ~~Steet~~St., Suite 300 Berkeley, California (Address of principal executive offices) 94704 (Zip Code)

Registrant’s telephone number, including area code: (707) 400-0778

N/A

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

¨	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act: None.

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company x

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 54.0201 ~~Departure~~Changes ofin ~~Directors~~Registrant’s orCertifying ~~Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers~~Accountant.

On February 27, 2026, the Audit Committee of the Board of Directors (cthe “Audit Committee”) ~~Appointment~~of Deep Fission, Inc. (the “Company”) approved the engagement of ~~Certain~~Grant ~~Officers~~Thornton LLP (“Grant Thornton”) as the Company’s independent registered public accounting firm to audit the Company’s consolidated financial statements for the fiscal years ended December 31, 2024 and 2025. Accordingly, dbbmckennon (“dbbmckennon”), the Company’s independent registered public accounting firm since September 5, 2025, was informed that it would be replaced as the Company’s independent registered public accounting firm effective February 27, 2026.

OnThe ~~February~~reports ~~18,~~of ~~2026,~~dbbmckennon ~~the~~on ~~Compensation Committee of~~ the ~~Board~~Company’s ofconsolidated ~~Directors~~financial ~~(the~~statements ~~“Compensation~~as ~~Committee”)~~ of ~~Deep~~and ~~Fission,~~for ~~Inc. (~~the ~~“Company”)~~fiscal ~~approved~~years ~~the~~ended ~~appointment~~December of31, ~~Mark~~2024 ~~Pérès as~~and ~~Chief~~2023 ~~Nuclear~~did ~~Officer~~not ofcontain ~~the~~an ~~Company,~~adverse ~~effective~~opinion ~~February~~or ~~19,~~a ~~2026,~~disclaimer ~~and approved the material terms~~ of ~~his~~opinion, nor ~~compensation~~were insuch ~~connection therewith.~~reports ~~The~~qualified ~~Board~~or ofmodified ~~Directors~~as ~~ratified~~to ~~Mr.~~uncertainty, ~~Pérès’s~~audit ~~appointment~~scope onor ~~February~~accounting 19principles, ~~2026.~~except ~~Mr.~~that ~~Pérès~~such ~~has been~~reports ~~designated~~ included an ~~“executive~~explanatory ~~officer”~~paragraph ~~within~~regarding ~~the~~substantial ~~meaning~~doubt ofabout ~~Rule 3b-7 under~~ the ~~Securities~~Company’s ~~Exchange~~ability ~~Act~~to ofcontinue ~~1934,~~ as ~~amended (the “Exchange Act”), and~~ a ~~“Section~~going ~~16 officer” for purposes of Section 16 of the Exchange Act~~concern.

InDuring ~~connection~~the ~~with~~fiscal ~~his~~years ~~appointment~~ended December 31, 2024 and 2023 and the ~~Company~~subsequent interim ~~extended~~period anthrough ~~offer~~February ~~letter~~27, 2026, there were no (i) disagreements (as defined in Item 304(a)(1)(iv) of Regulation S-K and the torelated ~~Mr.~~instructions ~~Pérès~~thereto) with dbbmckennon on any matter of accounting principles or practices, financial statement disclosure or auditing scope or procedure, which hedisagreements, ~~accepted.~~if ~~Pursuant~~not resolved to dbbmckennon’s satisfaction, would have caused dbbmckennon to make reference to the ~~offer~~subject ~~letter~~matter thereof in connection with its reports, ~~Mr.~~or ~~Pérès~~(ii) ~~will~~reportable ~~receive~~events an(as ~~annual~~defined ~~base~~in ~~salary~~Item 304(a)(1)(v) of ~~$300~~Regulation S-K and the related instructions thereto),~~000~~ other than, aas ~~target~~previously ~~annual~~disclosed ~~bonus~~in ~~opportunity~~the ~~equal~~Company’s toQuarterly ~~30%~~Report on ofForm ~~his~~10-Q ~~base~~for ~~salary,~~the ~~with~~quarter ~~actual~~ended ~~bonus~~September ~~amounts~~30, ~~if any~~2025, ~~determined~~the Company identified a material weakness in ~~the~~internal ~~discretion~~control over financial reporting related to the design and operating effectiveness of controls over the ~~Compensation~~Company’s ~~Committee~~financial reporting process, including the formalization and documentation of controls and management review procedures commensurate with a ~~grant~~public reporting company. The Audit Committee discussed the material weakness with dbbmckennon and has authorized dbbmckennon to respond fully to inquiries of ~~25,000~~Grant ~~restricted~~Thornton concerning ~~stock~~such ~~units~~material ~~(“RSUs”)~~weakness. ~~under~~Such material weakness did not result in any restatement of the Company’s ~~2025~~financial ~~Equity~~statements ~~Incentive~~and ~~Plan~~did not give rise to any disagreement between the Company and dbbmckennon.

The ~~RSUs~~Company ~~will~~has ~~have~~provided adbbmckennon ~~vesting~~with ~~commencement~~a ~~date~~copy of ~~February~~the ~~18, 2026~~foregoing disclosures and ~~are~~has ~~subject~~requested tothat ~~both~~dbbmckennon afurnish ~~service-based~~the ~~vesting~~Company ~~condition~~with ~~and~~ a ~~liquidity~~letter ~~event~~addressed ~~condition. Pursuant~~ to the ~~service-based~~Securities ~~condition,~~and ~~25%~~Exchange Commission ofstating ~~the~~whether ~~RSUs~~it ~~will~~agrees ~~vest~~with on the ~~first~~statements ~~anniversary~~made ofherein ~~the~~and, ~~vesting~~if ~~commencement~~not, ~~date~~stating ~~and~~ the ~~remaining~~respects ~~75% will vest~~ in ~~substantially~~which ~~equal quarterly~~it ~~installments~~does ~~over~~not ~~the~~agree. ~~following~~A 36copy ~~months,~~of ~~subject to Mr. Pérès~~dbbmckennon’s ~~continued service through each applicable~~ ~~vesting~~letter ~~date.~~is ~~The~~filed ~~liquidity event condition will be satisfied upon the earlier of a change in control, initial public offering or direct listing of the Company,~~ as ~~further~~Exhibit ~~described in the applicable award agreement~~16.1 ~~The~~to ~~RSUs~~this ~~are~~Current ~~subject~~Report toon aForm ~~seven~~8-~~year expiration date~~K.

~~There~~During ~~are~~the nofiscal ~~arrangements~~years orended ~~understandings~~December ~~between~~31, ~~Mr.~~2024 ~~Pérès~~ and ~~any~~2023 ~~other~~and ~~person~~the ~~pursuant~~subsequent interim period through February 27, 2026, neither the Company nor anyone on its behalf consulted with Grant Thornton regarding (i) the application of accounting principles to ~~which~~a hespecified ~~was~~transaction, ~~appointed~~either ascompleted anor ~~officer~~proposed, or the type of audit opinion that might be rendered on the Company.’s ~~There~~financial ~~are~~statements, noand ~~family~~neither ~~relationships~~a ~~between~~written ~~Mr.~~report ~~Pérès~~nor oral advice was provided to the Company by ~~and~~Grant ~~any~~Thornton ~~director~~that orGrant ~~executive~~Thornton ~~officer~~concluded was ofan important factor considered by the Company in reaching a decision as to any accounting, auditing or financial reporting issue, or (ii) any matter that was either the subject of a disagreement (as defined in Item 304(a)(1)(iv) of Regulation S-K and ~~there~~the ~~are~~related noinstructions ~~transactions~~thereto) ~~involving~~or ~~Mr.~~a ~~Pérès~~reportable ~~requiring~~event ~~disclosure~~(as defined ~~under~~in Item ~~404~~304(a)(1)(v) of Regulation S-K and the related instructions thereto).

~~Biographical~~Item ~~Information~~ 9.01 Financial Statements and Exhibits.

Mark Pérès was appointed Chief Nuclear Officer of Deep Fission effective February 19, 2026. Prior to his appointment, he served as the Company’s Vice President of Engineering since October 2024. In that role, he managed engineering and technical operations relating to Deep Fission’s nuclear reactor design. From 2019 to 2022, Mr. Pérès served as Vice President of Engineering at Kairos Power, where he directed design efforts for the Hermes Test Reactor. From 2009 to 2019, he served as Executive Project Director at Fluor, where he led major nuclear project deliveries, including work relating to the NuScale SMR, the first NRC-certified small modular reactor design under 10 C.F.R. Part 52. Mr. Pérès holds a B.S. in Mechanical Engineering from Montana State University, an M.S. in Mechanical Engineering from Washington State University, and is a PhD Candidate (ABD) and Adjunct Professor in Nuclear Engineering at the University of South Carolina.

Exhibit No.		Description
16.1		Letter from dbbmckennon as to the change in certifying accountant dated March 5, 2026
104		Cover Page Interactive Data File (Inline XBRL)

~~(e) Compensatory Arrangements of Certain Officers.~~SIGNATURE

OnPursuant ~~February~~to ~~18, 2026,~~ the ~~Compensation~~requirements ~~Committee~~of ~~approved an increase in~~ the ~~target~~Securities ~~annual~~Exchange ~~bonus~~Act ~~opportunity~~ of ~~Elizabeth Muller~~1934, the ~~Company’s~~registrant ~~Co-Founder,~~has ~~Chair~~duly ofcaused ~~the~~this ~~Board,~~report ~~President and Chief Executive Officer, from 50%~~ to ~~100%~~be ofsigned ~~her~~on ~~base~~its ~~salary,~~behalf ~~effective~~by ~~for fiscal year 2026. The actual bonus amount, if any, will be determined in~~ the ~~discretion~~ ofundersigned ~~the~~hereunto ~~Compensation~~duly ~~Committee~~authorized.

On February 18, 2026, the Compensation Committee approved a one-time cash bonus of $380,000 for Elizabeth Muller, the Company’s Co-Founder, Chair of the Board, President and Chief Executive Officer. The bonus was paid in January 2026 via special payroll outside the Company’s normal payroll cycle.

	DEEP FISSION, INC.

Date: March 5, 2026	/s/ JON GORDON
	Jon Gordon
	General Counsel & Secretary

On February 18, 2026, the Compensation Committee also approved an increase in the annual base salary of Mark Schmitz, the Company’s Chief Financial Officer, from $250,000 to $300,000, effective February 1, 2026. Mr. Schmitz’s target annual bonus opportunity remains 30% of his base salary. No other material changes were made to his compensatory arrangements.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	DEEP FISSION, INC.
Date: February 24, 2026	/s/ JON GORDON
	Jon Gordon
	General Counsel & Secretary

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