Registration Statement - Specified Transactions (Form S-3)

Subject to completion, dated November 4, 2026

PROSPECTUS

$300,000,000
Common Stock
Preferred Stock
Debt Securities
Warrants
Rights
Units

We may offer and sell up to $300,000,000 in the aggregate of the securities identified above from time to time in one or more offerings. This prospectus provides you with a general description of the securities.

Each time we offer and sell securities, we will provide a supplement to this prospectus that contains specific information about the offering and the amounts, prices and terms of the securities. The supplement may also add, update or change information contained in this prospectus with respect to that offering. You should carefully read this prospectus and the applicable prospectus supplement before you invest in any of our securities.

We may offer and sell the securities described in this prospectus and any prospectus supplement to or through one or more underwriters, dealers and agents, or directly to purchasers, through a combination of these methods or by any method that is deemed an "at the market offering" as defined in Rule 415(a)(4) under the Securities Act. If any underwriters, dealers or agents are involved in the sale of any of the securities, their names and any applicable purchase price, fee, commission or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. See the sections of this prospectus entitled "About this Prospectus" and "Plan of Distribution" for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

We are an "emerging growth company" as defined in Section 2(a) of the Securities Act of 1933, as amended (the "Securities Act"), and are subject to reduced public company reporting requirements. This prospectus complies with the requirements that apply to an issuer that is an emerging growth company.

INVESTING IN OUR SECURITIES INVOLVES RISKS. SEE "RISK FACTORS" ON PAGE 9 OF THIS PROSPECTUS AND ANY SIMILAR SECTION CONTAINED IN THE APPLICABLE PROSPECTUS SUPPLEMENT CONCERNING FACTORS YOU SHOULD CONSIDER BEFORE INVESTING IN OUR SECURITIES.

Our common stock, par value $0.0001 per share ("Common Stock"), is traded on The Nasdaq Global Market ("Nasdaq") under the symbol "FISN". On November 3, 2026, the closing price of our Common Stock was $2.67.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is           , 2026

TABLE OF CONTENTS

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission (the "SEC"), using the "shelf" registration process. By using a shelf registration statement, we may sell securities from time to time and in one or more offerings up to a total dollar amount of $300,000,000 as described in this prospectus. Each time that we offer and sell securities, we will provide a prospectus supplement to this prospectus that contains specific information about the securities being offered and sold and the specific terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. The prospectus supplement or free writing prospectus may also add, update or change information contained in this prospectus with respect to that offering. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement or free writing prospectus, you should rely on the prospectus supplement or free writing prospectus, as applicable. Before purchasing any securities, you should carefully read both this prospectus and the applicable prospectus supplement (and any applicable free writing prospectuses), together with the additional information described under the heading "Where You Can Find More Information; Incorporation by Reference."

We have not authorized anyone to provide you with any information or to make any representations other than those contained in this prospectus, any applicable prospectus supplement or any free writing prospectuses prepared by or on behalf of us or to which we have referred you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We will not make an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus and the applicable prospectus supplement to this prospectus is accurate only as of the date on its respective cover, that the information appearing in any applicable free writing prospectus is accurate only as of the date of that free writing prospectus, and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, unless we indicate otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates. This prospectus incorporates by reference, and any prospectus supplement or free writing prospectus may contain and incorporate by reference, market data and industry statistics and forecasts that are based on independent industry publications and other publicly available information. Although we believe these sources are reliable, we do not guarantee the accuracy or completeness of this information and we have not independently verified this information. In addition, the market and industry data and forecasts that may be included or incorporated by reference in this prospectus, any prospectus supplement or any applicable free writing prospectus may involve estimates, assumptions and other risks and uncertainties and are subject to change based on various factors, including those discussed under the heading "Risk Factors" contained in this prospectus, the applicable prospectus supplement and any applicable free writing prospectus, and under similar headings in other documents that are incorporated by reference into this prospectus. Accordingly, investors should not place undue reliance on this information.

When we refer to "Deep Fission," "we," "our," "us" and the "Company" in this prospectus, we mean Deep Fission, Inc. and its consolidated subsidiaries, unless otherwise specified. When we refer to "you," we mean the potential holders of the applicable series of securities.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus includes statements that express our opinions, expectations, beliefs, plans, objectives, assumptions or projections regarding future events or future results and therefore are, or may be deemed to be, "forward-looking statements." We intend such forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended (the "Exchange Act"). These forward-looking statements can generally be identified by the use of forward-looking terminology, including the terms "may," "will," "could," "should," "expects," "anticipates," "intends," "plans," "believes," "seeks," "estimates," "continue," "might," "possible," "potential," "predict," "project," "goal," "would," "commit" or, in each case, their negative or other variations or comparable terminology. These forward-looking statements include all matters that are not historical facts. They appear in a number of places throughout this prospectus (including in information that is incorporated into this prospectus) and include statements regarding our intentions, beliefs or current expectations concerning, among other things, results of operations, financial condition, liquidity, prospects, growth, strategies and the markets in which we operate. Such forward-looking statements are based on available current market material and management's expectations, beliefs and forecasts concerning future events impacting the Company. Factors that may impact such forward-looking statements include:

•

our future results of operations and financial condition;

​

•

our business strategy, including our commercialization strategy and our ability to generate revenue and the expected function and benefits of our Gravity Nuclear Reactor ("Gravity Reactor") design and related boreholes;

​

•

our plans, objectives and expectations for our business;

​

•

our phased deployment plan, including our targeted or expected timelines;

​

•

our operations and technology, including the development of our technology according to our expectations;

​

•

the targeted electrical generation capacity and safety expectations of our reactors;

​

•

our current expectations and targets for reactors with 2x2 fuel assembly configurations and 3x3 fuel assembly configurations;

​

•

our expectations regarding experiences and efficiencies gained through deployments and the impact on later deployments;

​

•

our financial estimates, including per reactor capital costs of deployment, annual cash operating expenses per reactor, annual revenue generation per reactor and annual cash contribution per reactor, in each case whether for 2x2 fuel assembly configurations or 3x3 fuel assembly configurations;

​

•

the requirement to, and ability to obtain, regulatory approvals, including licensing with the NRC (as defined below);

​

•

our expectations regarding our potential customer group;

​

•

our expectations regarding our intellectual property protection, including securing or maintaining any patents;

​

•

the period over which we anticipate our existing cash will be sufficient to operate our business;

​

•

our expected costs and the timeline for those costs, including the amount of additional capital required to complete development of, and license and commercially deploy, our first commercial reactor, and the availability of potential financings to obtain such additional capital; and

​

•

the assumptions underlying or relating to any of the foregoing.

​

The forward-looking statements contained in this prospectus are based on our current expectations and beliefs concerning future developments and their potential effects on the Company. These statements are based upon information available to us as of the date of this prospectus, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and

WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE

Available Information

We file reports, proxy statements and other information with the SEC. The SEC maintains a website that contains reports, proxy and information statements and other information about issuers, such as us, who file electronically with the SEC. The address of that website is www.sec.gov.

Our website address is www.deepfission.com. The information on our website is not, and should not be deemed to be, a part of this prospectus.

This prospectus and any prospectus supplement are part of a registration statement that we filed with the SEC and do not contain all of the information in the registration statement. The full registration statement may be obtained from the SEC or us, as provided below. Forms of the indenture and other documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement or documents incorporated by reference in the registration statement. Statements in this prospectus or any prospectus supplement about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the actual documents for a more complete description of the relevant matters. You may inspect a copy of the registration statement through the SEC's website, as provided above.

Incorporation by Reference

The SEC's rules allow us to "incorporate by reference" information into this prospectus, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, and subsequent information that we file with the SEC will automatically update and supersede that information. Any statement contained in this prospectus or a previously filed document incorporated by reference will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or a subsequently filed document incorporated by reference modifies or replaces that statement.

This prospectus and any accompanying prospectus supplement incorporate by reference the documents set forth below that have previously been filed with the SEC (other than documents or information deemed to have been furnished and not filed in accordance with SEC rules):

•

Our Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on April 15, 2026.

​

•

The information specifically incorporated by reference into our Annual Report on Form 10-K from our Definitive Proxy Statement on Schedule 14A, filed with the SEC on June 17, 2026.

​

•

Our Quarterly Reports on Form 10-Q for the periods ended March 31, 2026, June 30, 2026 and September 30, 2026, filed with the SEC on May 8, 2026, August 3, 2026 and November 4, 2026, respectively.

​

•

Our Current Reports on Form 8-K filed with the SEC on February 10, 2026, February 25, 2026, March 5, 2026, April 9, 2026, June 22, 2026, July 17, 2026 and July 29, 2026.

​

•

The description of our Common Stock contained in our Form 8-A12B filed with the SEC on May 28, 2026.

​

All reports and other documents we subsequently file pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act, prior to the termination of the registration statement of which this prospectus forms a part, including all such documents we may file with the SEC after the date of the initial registration statement and prior to the effectiveness of the registration statement, but excluding any information furnished to, rather than filed with, the SEC, will also be incorporated by reference into this prospectus and deemed to be part of this prospectus from the date of the filing of such reports and documents.

You may request a free copy of any of the documents incorporated by reference in this prospectus by writing or telephoning us at the following address:

Deep Fission, Inc.
2001 Addison Street, Suite 300
Berkeley, California 94704
(707) 400-0778

Exhibits to the filings will not be sent, however, unless those exhibits have specifically been incorporated by reference in this prospectus or any accompanying prospectus supplement.

THE COMPANY

Company Overview

We are an early-stage nuclear energy technology company developing a small modular reactor based on established pressurized water reactor ("PWR") technology, with novel emplacement in deep boreholes approximately one mile below the Earth's surface. Our reactor, which we refer to as the Gravity Reactor, is designed to leverage subsurface conditions to support key containment and operating functions, including the use of hydrostatic pressure from a water column within the borehole to support reactor operating pressure and cooling, and the surrounding geological formation to provide structural confinement and shielding. This approach is intended to reduce reliance on large surface containment structures and other safety-related infrastructure associated with conventional nuclear power plants, and is designed to support faster deployment timelines, improve security, enhance safety, and enable lower capital and operating costs relative to conventional nuclear facilities, while potentially reducing exposure to environmental and other surface-level hazards.

Each 3x3 Gravity Reactor is targeted to produce up to 15 megawatts of electric power output ("MWe"). Individual reactors may be deployed as standalone installations or grouped in clusters of boreholes at a single site, which may enable longer refueling cycles through coordinated fuel management, staggered refueling schedules and more efficient utilization of shared infrastructure, and support larger installations capable of supplying hundreds and potentially thousands of MWe of generation capacity.

Our commercialization strategy is based on a phased deployment plan under which we are targeting initial commercial deployment as early as 2027. Given that reactor criticality using established PWR technology is well understood, we are prioritizing validation of the hardest and most differentiated parts of our system, to reduce risk earlier and move more directly toward a commercialization outcome. Our key demonstration objectives include drilling to depth at commercial scale, installing and integrating a nuclear system a mile underground, and operating as part of a complete energy ecosystem. Critically, we aim to prove that each of these milestones can be achieved on a timeline sufficient to meet the AI-driven surge in demand for energy. We are currently participating in the U.S. Department of Energy ("DOE") Reactor Pilot Program and expect to demonstrate our system as part of that program.

The first phase of our phased deployment plan involves engineering validation and proof of concept wells. We have a long-term lease for approximately 100 acres located within the Great Plains Industrial Park in Parsons, Kansas (the "Kansas Site") and have commenced initial field development activities at the site. As part of this phase, we have already completed our first data acquisition well to gather real-world data up to 6,000 feet deep. We are currently advancing our second, near full-scale proof-of-concept well, which is intended to further validate our drilling and emplacement approach. We continue to advance our reactor design in parallel with these activities, including planning additional drilling activities and conducting related engineering, safety analysis and emplacement work, and we are targeting completion of these activities in the coming months. In September 2026, the Company entered into a non-binding memorandum of understanding with Youngquist Brothers, LLC ("Youngquist") to evaluate and test drilling and borehole-construction methods to support the Company's underground reactor deployment model. Neither party is obligated to enter into a definitive agreement or pursue any project beyond the evaluation and testing contemplated by the memorandum of understanding, and there can be no assurance that the collaboration will result in a commercial agreement, a broader or longer-term commercial relationship, or any future project. In September 2026, we lowered a full-size prototype canister into a 34-inch-wide borehole, aligned it and brought it back to the surface. The balance of this year and into 2027 will be focused on the delivery of key components for full-system installation, including well casing, our reactor canister, and heat exchanger, as well as low-enriched uranium fabrication and loading.

The second phase of our phased deployment plan involves DOE authorization and one or more commercial pilot wells. In July 2026, the DOE approved our Nuclear Safety Design Agreement for the Gravity Reactor, allowing us to advance to the next phase of the DOE review process, including submission of a Preliminary Documented Safety Analysis. Subject to further DOE authorization, we intend to demonstrate the Gravity Reactor, and apply for a commercial license with the U.S. Nuclear Regulatory Commission ("NRC") in the first half of 2027, converting the same pilot reactor to commercial operation.

We are working closely with both the DOE and the NRC to align demonstration and licensing, as we are aiming to move these efforts forward together rather than advancing them in sequence.

The third and final phase of our phased deployment plan involves the construction of surface facilities and seeking high-volume commercial licensing for deployment of multiple reactors at a single site through clustered boreholes, and subsequently, at multiple sites. We are targeting as early as 2027 to seek such high-volume commercial licensing with the NRC, and anticipate at least a one-year lag between the start of construction and revenue recognition. We are targeting initial commercial deployment as early as 2027 of up to 5 MWe, which we expect to connect directly to transmission lines. This initial deployment is separate from our Master Energy Purchase Agreement with the Great Plains Development Authority, which covers an initial phase of 150 MW at the Great Plains Industrial Park targeted for commercial operation in September 2028.

Our approach to subsurface reactor deployment is supported by our intellectual property portfolio, which includes issued patents and pending patent applications relating to reactor configuration, deep subsurface emplacement, drilling and casing techniques, thermal-hydraulic performance, instrumentation and monitoring, and other technologies supporting the deployment of underground nuclear reactors. We believe that our intellectual property, together with our engineering expertise and ongoing development activities, supports our competitive position.

Legacy Deep Fission (as defined below) was incorporated in July 2023 and remains in the development stage. The Gravity Reactor remains in conceptual and early engineering stages, and we have not constructed or operated a commercial reactor or generated revenue. Current activities include reactor development, geological evaluation, large-diameter borehole drilling research and development, geothermal testing, safety analysis, regulatory engagement, site development, and commercialization planning.

Corporate Information

We were incorporated as Surfside Acquisition Inc. ("Surfside") in the State of Delaware on December 10, 2021. Prior to the Merger (as defined below), we were a "shell company" ​(as defined in Rule 12b-2 under the Exchange Act). On September 5, 2025, Surfside completed a merger (the "Merger") with Deep Fission Nuclear, Inc. (formerly known as Deep Fission, Inc.), a private Delaware corporation ("Legacy Deep Fission"), pursuant to an Agreement and Plan of Merger and Reorganization (the "Merger Agreement"), under which a wholly owned subsidiary of Surfside merged with and into Legacy Deep Fission, with Legacy Deep Fission continuing as the surviving corporation and becoming a wholly owned subsidiary of Surfside. In connection with the transaction, Surfside changed its name to Deep Fission, Inc. For financial reporting purposes, the transaction was treated as a recapitalization and reverse acquisition, with Legacy Deep Fission considered the accounting acquirer.

Our Common Stock is listed on Nasdaq under the symbol "FISN." The mailing address of the Company's principal executive office is 2001 Addison Street, Suite 300, Berkeley, California 94704. Our telephone number is (707) 400-0778. Our website address is www.deepfission.com. The information contained in, or accessible through, our website does not constitute a part of this prospectus. We have included our website address in this prospectus solely as an inactive textual reference.

Emerging Growth Company

As a company with less than $1.235 billion in revenue during our last fiscal year, we qualify as an "emerging growth company" as defined in the Jumpstart Our Business Startups Act of 2012, as amended (the "JOBS Act"). An "emerging growth company" may take advantage of reduced reporting requirements that are otherwise applicable to public companies that are not emerging growth companies. These provisions include, but are not limited to:

•

not being required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act of 2002, as amended;

​

•

not being required to comply with any requirement that may be adopted by the Public Company Accounting Oversight Board regarding mandatory audit firm rotation or a supplement to the auditor's

​

report providing additional information about the audit and the financial statements (i.e., an auditor discussion and analysis);

•

reduced disclosure obligations regarding executive compensation in our periodic reports, proxy statements and registration statements; and

​

•

exemptions from the requirements of holding a nonbinding advisory vote of stockholders on executive compensation, stockholder approval of any golden parachute payments not previously approved and having to disclose the ratio of the compensation of our chief executive officer to the median compensation of our employees.

​

We may take advantage of these provisions until the last day of our fiscal year following the fifth anniversary of the completion of the Company's initial public offering, which will be December 31, 2031. However, if (i) our annual gross revenue exceeds $1.235 billion, (ii) we issue more than $1.0 billion of non-convertible debt in any three-year period or (iii) we become a "large accelerated filer" ​(as defined in Rule 12b-2 under the Exchange Act) prior to the end of such five-year period, we will cease to be an emerging growth company. We will be deemed to be a "large accelerated filer" at such time that we (a) have an aggregate worldwide market value of common equity securities held by non-affiliates of $700.0 million or more as of the last business day of our most recently completed second fiscal quarter, (b) have been required to file annual and quarterly reports under the Exchange Act for a period of at least 12 months and (c) have filed at least one annual report pursuant to the Exchange Act.

We have elected to take advantage of certain of the reduced disclosure obligations in the registration statement of which this prospectus is a part and may elect to take advantage of other reduced reporting requirements in future filings. As a result, the information that we provide to our stockholders may be different than you might receive from other public reporting companies in which you hold equity interests.

In addition, the JOBS Act provides that an emerging growth company can take advantage of an extended transition period for complying with new or revised accounting standards. We have elected to use the extended transition period for complying with new or revised accounting standards. As a result of this election, our financial statements may not be comparable to companies that comply with public company effective dates.

Smaller Reporting Company

We are also a "smaller reporting company" under the Exchange Act. We may continue to be a smaller reporting company so long as, as of June 30 of the preceding year, (i) the market value of our voting and non-voting equity held by non-affiliates, or our public float, is less than $250 million; or (ii) we have annual revenues less than $100 million and either we have no public float or our public float is less than $700 million. If we are a smaller reporting company at the time we cease to be an emerging growth company, we may continue to rely on exemptions from certain disclosure requirements that are available to smaller reporting companies. Specifically, as a smaller reporting company we may choose to present only the two most recent fiscal years of audited financial statements in our Annual Report on Form 10-K and, similar to emerging growth companies, smaller reporting companies have reduced disclosure obligations regarding executive compensation.

RISK FACTORS

Investment in any securities offered pursuant to this prospectus and the applicable prospectus supplement involves risks. Before deciding whether to invest in our securities, you should carefully consider the risk factors incorporated by reference to our most recent Annual Report on Form 10-K and any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K, and all other information contained or incorporated by reference into this prospectus, as updated by our subsequent filings under the Exchange Act, and the risk factors and other information contained in the applicable prospectus supplement and any applicable free writing prospectus. The occurrence of any of these risks might cause you to lose all or part of your investment in the offered securities. There may be other unknown or unpredictable economic, business, competitive, regulatory or other factors that could have material adverse effects on our future results. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow could be seriously harmed. This could cause the trading price of our securities to decline, resulting in a loss of all or part of your investment. Please also carefully read the section entitled "Cautionary Note on Forward-Looking Statements" included in our most recent Annual Report on Form 10-K and any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K.

USE OF PROCEEDS

We intend to use the net proceeds from the sale of the securities as set forth in the applicable prospectus supplement.

DESCRIPTION OF CAPITAL STOCK

The following description of our capital stock is not complete and may not contain all the information you should consider before investing in our capital stock. This description is summarized from, and qualified in its entirety by reference to, our amended and restated certificate of incorporation (our "Certificate of Incorporation") and our amended and restated bylaws (our "Bylaws"), each of which has been publicly filed with the SEC, as well as the relevant provisions of the General Corporation Law of the State of Delaware ("DGCL"). See "Where You Can Find More Information; Incorporation by Reference."

General

We have authorized capital stock consisting of 300,000,000 shares of Common Stock, par value $0.0001 per share, and 10,000,000 shares of preferred stock, par value $0.0001 per share.

Common Stock

Dividend Rights

Subject to applicable law and the rights and preferences, if any, of any holders of any outstanding series of our preferred stock, the holders of our Common Stock are entitled to receive dividends if our board of directors, in its discretion, determines to issue dividends and then only at the times and in the amounts that our board of directors may determine, payable either in cash, in property or in shares of our capital stock or other securities.

Voting Rights; Classified Board

Holders of our Common Stock are entitled to one vote for each share of Common Stock held on all matters submitted to a vote of stockholders. Except as otherwise required by law, holders of our common stock are not entitled to vote on any amendment to the Certificate of Incorporation (including any certificate of designation relating to any series of preferred stock) that relates solely to the terms of one or more outstanding series of preferred stock if the holders of such affected series are entitled, either separately or together as a class with the holders of one or more other such series, to vote on such amendment pursuant to the Certificate of Incorporation (including any certificate of designation relating to any series of preferred stock).

We have not provided for cumulative voting for the election of directors in our Certificate of Incorporation. Accordingly, holders of a majority of the shares of our Common Stock will be able to elect all of our directors.

Subject to the rights of the holders of any one or more series of preferred stock to elect additional directors under specified circumstances, our Certificate of Incorporation establishes a classified board of directors, divided into three classes with staggered three-year terms. Only one class of directors will be elected at each annual meeting of our stockholders, with the other classes continuing for the remainder of their respective three-year terms, until their respective successors are duly elected and qualified.

No Preemptive or Similar Rights

Our Common Stock is not entitled to preemptive rights and is not subject to conversion, redemption or sinking fund provisions.

Right to Receive Liquidation Distributions

Upon our liquidation, dissolution, or winding-up, the holders of our Common Stock would be entitled to receive pro rata all assets remaining available for distribution to holders of such shares.

Preferred Stock

Our board of directors is authorized, subject to limitations prescribed by Delaware law, to issue preferred stock in one or more series, to establish from time to time the number of shares to be included in

each series, and to fix the designation, vesting, powers (including voting powers), preferences, and relative, participating, optional or other rights of the shares of each series and any of its qualifications, limitations, or restrictions, in each case without further vote or action by our stockholders.

Our board of directors can also increase or decrease the number of shares of any series of preferred stock, but not below the number of shares of that series then outstanding or above the total number of authorized shares of the class, without any further vote or action by our stockholders. Our board of directors may, without stockholder approval, authorize the issuance of preferred stock with priorities and voting, dividend or other rights that could adversely affect the voting power or other rights of the holders of our Common Stock and could have anti-takeover effects. The issuance of preferred stock, while providing flexibility in connection with possible acquisitions and other corporate purposes, could, among other things, have the effect of delaying, deferring, or preventing a change in our control or the removal of existing management and might adversely affect the market price of our Common Stock.

Stock Options

The Company approved and adopted the post-Merger 2025 Equity Incentive Plan and reserved 9,500,884 shares of our Common Stock for future issuances of incentive awards under the post-Merger 2025 Equity Incentive Plan at the discretion of our officers, employees, consultants and directors.

Registration Rights Agreements

On September 5, 2025, Surfside completed the Merger with Legacy Deep Fission, the Merger Agreement under which a wholly owned subsidiary of Surfside merged with and into Legacy Deep Fission, with Legacy Deep Fission continuing as the surviving corporation and becoming a wholly owned subsidiary of Surfside. In connection with the transaction, Surfside changed its name to Deep Fission, Inc.

In connection with the Merger and the issuance and sale of 10,000,000 shares of our Common Stock in a private placement to certain accredited and institutional investors at a purchase price of $3.00 per share (the "2025 Private Placement"), we entered into a registration rights agreement (the "2025 Registration Rights Agreement"), pursuant to which we agreed that promptly, but no later than 45 calendar days after the date of filing the Current Report on Form 8-K relating to the closing of the 2025 Private Placement, we would file, subject to customary exceptions, a registration statement, and cause such registration statement to become effective and remain effective, current and up-to-date for a period of five years after the effective date of the registration statement or for a shorter period ending on the date on which there are no longer any 2025 Registrable Shares (as defined below) outstanding, with the SEC covering sale, transfer or disposition of the (i) the shares of our Common Stock issued in the 2025 Private Placement; (ii) the shares of our Common Stock issuable upon exercise of the warrants issued to each of the U.S. registered broker-dealers acting as placement agents in connection with the 2025 Private Placement; (iii) the shares of our Common Stock issued in exchange for all of the equity securities of Legacy Deep Fission that were outstanding immediately prior to the closing of the Merger; (iv) the shares of Common Stock retained by Surfside's existing stockholders prior to the closing of the Merger; and (v) shares of our Common Stock issued to an advisor in exchange for services rendered in connection with the Merger ((i) - (v) collectively, the "2025 Registrable Shares"), for so long as they are "Registrable Securities" as defined in the 2025 Registration Rights Agreement, subject to the prior receipt by the Company of the selling stockholder information regarding the holders of the 2025 Registrable Shares required to be included in the registration statement under applicable SEC rules and regulations.

In connection with the closing of the issuance and sale of an aggregate of 5,333,333 shares of Common Stock in a private placement to certain accredited and institutional investors at a purchase price of $15.00 per share (the "2026 Private Placement"), we entered into a registration rights agreement (the "2026 Registration Rights Agreement") pursuant to which we agreed that promptly, but no later than 30 calendar days after the date of closing of the 2026 Private Placement, we would file, subject to customary exceptions, a registration statement, and cause such registration statement to become effective and remain effective, current and up-to-date for a period of five years after the effective date of the registration statement or for a shorter period ending on the date on which there are no longer any 2026 Registrable Shares (as defined below) outstanding, with the SEC, covering sale, transfer or disposition of the shares of our Common Stock issued in the 2026 Private Placement and the shares of our Common Stock issuable upon exercise of

the warrants issued to each of the U.S. registered broker-dealers acting as placement agents in connection with the 2026 Private Placement (the "2026 Registrable Shares"), for so long as they are "Registrable Securities" as defined in the 2026 Registration Rights Agreement, subject to the prior receipt by the Company of the selling stockholder information regarding the holders of the 2026 Registrable Shares required to be included in the registration statement under applicable SEC rules and regulations.

Anti-Takeover Provisions

Certain provisions of the DGCL, our Certificate of Incorporation, and our Bylaws could have the effect of delaying, deferring, or discouraging another person from acquiring control of our Company by means of a tender offer, a proxy contest or otherwise, or to remove incumbent officers and directors. These provisions, which are summarized below, are expected to discourage certain types of coercive takeover practices and inadequate takeover bids and encourage persons seeking to acquire control of our Company to first negotiate with our board of directors. We believe that the benefits of increased protection of our potential ability to negotiate with an unfriendly or unsolicited acquirer outweigh the disadvantages of discouraging a proposal to acquire us because negotiation of these proposals could result in an improvement of their terms. However, these provisions may delay, deter or prevent a merger or acquisition of us that a stockholder might consider is in their best interest or in our best interests, including transactions that might result in a premium over the prevailing market price of our Common Stock.

Section 203 of the DGCL

We are subject to the provisions of Section 203 of the DGCL regulating corporate takeovers. In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a "business combination" with an "interested stockholder" for a three-year period following the time that this stockholder becomes an interested stockholder, unless the business combination is approved in a prescribed manner as summarized below. Under Section 203, a business combination between a corporation and an interested stockholder is prohibited unless it satisfies one of the following conditions:

•

before the stockholder became interested, our board of directors approved either the business combination or the transaction which resulted in the stockholder becoming an interested stockholder;

​

•

upon consummation of the transaction which resulted in the stockholder becoming an interested stockholder, the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the voting stock outstanding shares owned by persons who are directors and also officers, and employee stock plans in some instances, but not the outstanding voting stock owned by the interested stockholder; or

​

•

at or after the time the stockholder became interested, the business combination was approved by our board of directors and authorized at an annual or special meeting of the stockholders by the affirmative vote of at least two-thirds of the outstanding voting stock which is not owned by the interested stockholder.

​

Section 203 defines a business combination to include:

•

any merger or consolidation involving the corporation and the interested stockholder;

​

•

any sale, transfer, lease, pledge, or other disposition involving the interested stockholder of 10% or more of the assets of the corporation;

​

•

subject to exceptions, any transaction that results in the issuance or transfer by the corporation of any stock of the corporation to the interested stockholder;

​

•

subject to exceptions, any transaction involving the corporation that has the effect of increasing the proportionate share of the stock of any class or series of the corporation beneficially owned by the interested stockholder; and

​

•

the receipt by the interested stockholder of the benefit of any loans, advances, guarantees, pledges or other financial benefits provided by or through the corporation.

​

In general, Section 203 defines an interested stockholder as any entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation and any entity or person affiliated with or controlling or controlled by the entity or person.

Certificate of Incorporation and Bylaw Provisions

Our Certificate of Incorporation and our Bylaws include a number of provisions that may have the effect of deterring hostile takeovers, or delaying or preventing changes in our management team, our board of directors or our governance or policy, including the following:

•

Board Vacancies. Our Bylaws and Certificate of Incorporation provide, subject to the special rights of the holders of any series of preferred stock to elect directors, that any vacancy on the board of directors may be filled by the affirmative vote of a majority of the directors then in office, even if less than a quorum, or by a sole remaining director, and not by the stockholders, except as otherwise provided by law. Any director chosen to fill a vacancy will hold office until the expiration of the term of the class for which he or she was elected and until his or her successor is duly elected and qualified, or until his or her earlier death, resignation, disqualification or removal. In addition, the number of directors constituting the total number of authorized directors whether or not there exist any vacancies in previously authorized directorships can only be fixed by our board of directors. These provisions prevent a stockholder from increasing the size of our board of directors and gaining control of our board of directors by filling the resulting vacancies with its own nominees. This makes it more difficult to change the composition of the board of directors, which can promote continuity of management.

​

•

Classified Board. Our Certificate of Incorporation and Bylaws provide that our board of directors is classified into three classes of directors. The existence of a classified board of directors could delay a successful tender offeror from obtaining majority control of our board of directors, and the prospect of that delay might deter a potential offeror.

​

•

Directors Removed Only for Cause. Our Certificate of Incorporation provides that, subject to the special rights of the holders of any series of preferred stock to remove directors elected by such series of preferred stock, stockholders may remove directors only for cause and only by the affirmative vote of the holders of at least sixty-six and two-thirds percent of the voting power of the then-outstanding shares of our capital stock entitled to vote generally in the election of directors, voting together as a single class.

​

•

Requirements for Amendments of Our Certificate of Incorporation and Bylaws. Our Certificate of Incorporation further provides that the affirmative vote of holders of at least sixty-six and two-thirds percent of our capital stock entitled to vote generally in the election of directors, voting together as a single class, will be required to amend or repeal (or adopt provisions inconsistent with) certain provisions of our Certificate of Incorporation, including provisions relating to the classified board, the size of the board of directors, removal of directors, special meetings, actions by written consent, exculpation and exclusive forum. Our board of directors is expressly authorized to adopt, amend or repeal any provisions of our Bylaws. Our Bylaws may also be amended or repealed by the affirmative vote of holders of at least sixty-six and two-thirds percent of our capital stock entitled to vote generally in the election of directors, voting together as a single class.

​

•

Stockholder Action; Special Meetings of Stockholders. Our Certificate of Incorporation provides that our stockholders may not take action by written consent but may only take action at annual or special meetings of our stockholders, unless taking such action by consent in lieu of a meeting is approved by all directors of the Company then in office. As a result, holders of our capital stock would not be able to amend our Bylaws or remove directors without holding a meeting of our stockholders called in accordance with our Bylaws. Our Certificate of Incorporation and our Bylaws provide that special meetings of our stockholders may be called only by the chairperson of the board of directors, our chief executive officer or the board of directors, thus prohibiting a stockholder from calling a special meeting. These provisions might delay the ability of our stockholders to force consideration of a proposal or for stockholders to take any action, including the removal of directors.

​

•

Advance Notice Requirements for Stockholder Proposals and Director Nominations. Our Bylaws provide advance notice procedures for stockholders seeking to bring business before our annual

​

meeting of stockholders or to nominate candidates for election as directors at our annual meeting of stockholders. Our Bylaws also specify certain requirements regarding the form and content of a stockholder's notice. These provisions may make it more difficult for our stockholders to bring matters before our annual meeting of stockholders or make nominations for directors at our annual meeting of stockholders. These provisions may also discourage or deter a potential acquirer from conducting a solicitation of proxies to elect the acquirer's own slate of directors or otherwise attempting to obtain control of our Company.

•

No Cumulative Voting. The DGCL provides that stockholders are not entitled to the right to cumulate votes in the election of directors unless a corporation's certificate of incorporation provides otherwise. Our Certificate of Incorporation does not provide for cumulative voting.

​

•

Issuance of Undesignated Preferred Stock. Our Certificate of Incorporation provides our board of directors the authority, without further action by the stockholders, to issue up to 10,000,000 shares of undesignated preferred stock with rights and preferences, including voting rights, designated from time to time by our board of directors. The existence of authorized but unissued shares of preferred stock enables our board of directors to render more difficult or to discourage an attempt to obtain control of us by means of a merger, tender offer, proxy contest, or otherwise.

​

•

Choice of Forum. Our Certificate of Incorporation provides that, unless we consent in writing to the selection of an alternative forum and to the fullest extent permitted by law, the Court of Chancery of the State of Delaware (or, if and only if the Court of Chancery of the State of Delaware lacks subject matter jurisdiction, any state court located within the State of Delaware or, if and only if all such state courts lack subject matter jurisdiction, the federal district court for the District of Delaware) and any appellate court therefrom, will be the sole and exclusive forum for: (a) any derivative action, suit or proceeding brought on behalf of us; (b) any action, suit or proceeding asserting a claim of breach of a fiduciary duty owed by any current or former director, officer, employee, or agent of ours; (c) any action, suit or proceeding asserting a claim against us or any current or former director, officer or employee of ours arising out of or pursuant to, or seeking to enforce any right, obligation or remedy under, or to interpret, apply, or determine the validity of, any provision of the DGCL, the Certificate of Incorporation or the Bylaws (as each may be amended from time to time); (d) any action, suit or proceeding as to which the DGCL confers jurisdiction on the Court of Chancery of the State of Delaware; or (e) any action, suit or proceeding asserting a claim against us or any current or former director, officer or employee of ours governed by the internal affairs doctrine, in all cases subject to the court's having personal jurisdiction over the indispensable parties named as defendants. However, such forum selection provisions will not apply to actions, suits or proceedings brought to enforce any liability or duty created by the Exchange Act or any other claim for which the federal courts of the United States have exclusive jurisdiction. The Certificate of Incorporation also provides that, unless we consent in writing to the selection of an alternative forum, the federal district courts of the United States of America will be the exclusive forum for the resolution of any complaint asserting a cause of action arising under the Securities Act.

​

Section 22 of the Securities Act creates concurrent jurisdiction for federal and state courts over all claims brought to enforce any duty or liability created by the Securities Act or the rules and regulations thereunder. Accordingly, both state and federal courts have jurisdiction to entertain such claims. As noted above, the Certificate of Incorporation provides that the federal district courts of the United States will have exclusive jurisdiction over any action asserting a cause of action arising under the Securities Act. Accordingly, there is uncertainty as to whether a court would enforce such provision. Our stockholders will not be deemed to have waived our compliance with the federal securities laws and the rules and regulations thereunder.

Section 27 of the Exchange Act creates exclusive federal jurisdiction over all claims brought to enforce any duty or liability created by the Exchange Act or the rules and regulations thereunder. As noted above, the Certificate of Incorporation provides that the choice of forum provision does not apply to suits brought to enforce any duty or liability created by the Exchange Act. Accordingly, actions by our stockholders to enforce any duty or liability created by the Exchange Act or the rules and regulations thereunder must be brought in federal court. Our stockholders will not be deemed to have waived our compliance with the federal securities laws and the regulations promulgated thereunder.

Any person or entity purchasing or otherwise acquiring or holding any interest in shares of our capital stock shall be deemed to have notice of and consented to the forum selection provisions in the Certificate of Incorporation.

The choice of forum provisions may limit a stockholder's ability to bring a claim in a judicial forum that it finds favorable for disputes with us or our directors, officers, or other employees, which may discourage such lawsuits against us and our directors, officers, and other employees. Alternatively, if a court were to find the choice of forum provisions contained in the Certificate of Incorporation to be inapplicable or unenforceable in an action, we may incur additional costs associated with resolving such action in other jurisdictions, which could harm our business, results of operations, and financial condition.

Limitation on Liability and Indemnification of Directors and Officers

As permitted by the DGCL, our Certificate of Incorporation contains provisions that eliminate the personal liability of our directors and officers for monetary damages for breaches of their fiduciary duty as directors or officers to the fullest extent permitted by the DGCL as it now exists or may in the future be amended. The DGCL, as it now exists, permits a corporation to eliminate the personal liability of its directors and officers for monetary damages, except for liability:

•

for any breach of the director's or officer's duty of loyalty to the corporation or its stockholders;

​

•

for acts or omissions by the director or officer not in good faith or that involve intentional misconduct or a knowing violation of law;

​

•

of a director under Section 174 of the DGCL (regarding unlawful dividends and stock purchases);

​

•

for any transaction from which the director or officer derived an improper personal benefit; or

​

•

of any officer in an action by or in the right of the corporation.

​

The Bylaws provide that our directors and officers, and directors and officers of our predecessor, will be indemnified and advanced expenses by us to the fullest extent authorized or permitted by the DGCL as it now exists or may in the future be amended. The DGCL, as it now exists, permits a corporation to indemnify directors and officers for amounts actually and reasonably incurred by them if they acted in good faith and in a manner they reasonably believed to be in or not opposed to the best interests of the corporation and, with respect to any criminal action or proceeding, had no reasonable cause to believe their conduct was unlawful (subject to certain exceptions for actions brought by or in the right of the corporation).

The Bylaws also permit us to purchase and maintain insurance on behalf of any officer, director, employee or agent of ours for any liability arising out of his or her status as such, to the fullest extent permitted by the DGCL.

These provisions may discourage stockholders from bringing a lawsuit against our directors or officers for breach of their fiduciary duties. These provisions also may have the effect of reducing the likelihood of derivative litigation against our directors and officers, even though such an action, if successful, might otherwise benefit us or our stockholders. Furthermore, a stockholder's investment may be adversely affected to the extent we pay the costs of settlement and damage awards against our directors and officers pursuant to these indemnification provisions.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to our directors, officers and controlling persons pursuant to the foregoing provisions, or otherwise, in the opinion of the SEC, such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable.

Listing

Our shares of Common Stock are listed on Nasdaq under the symbol "FISN".

Transfer Agent and Registrar

The transfer agent and registrar for our Common Stock is VStock Transfer, LLC. The transfer agent's address is 18 Lafayette Place, Woodmere, NY 11598, and its telephone number is (212) 828-8436.

DESCRIPTION OF DEBT SECURITIES

The following description, together with the additional information we include in any applicable prospectus supplement or free writing prospectus, summarizes certain general terms and provisions of the debt securities that we may offer under this prospectus. When we offer to sell a particular series of debt securities, we will describe the specific terms of the series in a supplement to this prospectus. We will also indicate in the supplement to what extent the general terms and provisions described in this prospectus apply to a particular series of debt securities.

We may issue debt securities either separately, or together with, or upon the conversion or exercise of or in exchange for, other securities described in this prospectus. Debt securities may be our senior, senior subordinated or subordinated obligations and, unless otherwise specified in a supplement to this prospectus, the debt securities will be our direct, unsecured obligations and may be issued in one or more series.

The debt securities will be issued under an indenture between us and a trustee to be named in the applicable indenture, as trustee. We have summarized select portions of the indenture below. The summary is not complete. The form of the indenture has been filed as an exhibit to the registration statement and you should read the indenture for provisions that may be important to you. In the summary below, we have included references to the section numbers of the indenture so that you can easily locate these provisions. Capitalized terms used in the summary and not defined herein have the meanings specified in the indenture.

As used in this section only, "Deep Fission," "we," "our" or "us" refer to Deep Fission, Inc. excluding our subsidiaries, unless expressly stated or the context otherwise requires.

General

The terms of each series of debt securities will be established by or pursuant to a resolution of our board of directors and set forth or determined in the manner provided in a resolution of our board of directors, in an officer's certificate or by a supplemental indenture. (Section 2.2) The particular terms of each series of debt securities will be described in a prospectus supplement relating to such series (including any pricing supplement or term sheet).

We can issue an unlimited amount of debt securities under the indenture that may be in one or more series with the same or various maturities, at par, at a premium, or at a discount. (Section 2.1) We will set forth in a prospectus supplement (including any pricing supplement or term sheet) relating to any series of debt securities being offered, the aggregate principal amount and the following terms of the debt securities, if applicable:

•

the title and ranking of the debt securities (including the terms of any subordination provisions);

​

•

the price or prices (expressed as a percentage of the principal amount) at which we will sell the debt securities;

​

•

any limit on the aggregate principal amount of the debt securities;

​

•

the date or dates on which the principal of the securities of the series is payable;

​

•

the rate or rates (which may be fixed or variable) per annum or the method used to determine the rate or rates (including any commodity, commodity index, stock exchange index or financial index) at which the debt securities will bear interest, the date or dates from which interest will accrue, the date or dates on which interest will commence and be payable and any regular record date for the interest payable on any interest payment date;

​

•

the place or places where principal of, and interest, if any, on the debt securities will be payable (and the method of such payment), where the securities of such series may be surrendered for registration of transfer or exchange, and where notices and demands to us in respect of the debt securities may be delivered;

​

•

the period or periods within which, the price or prices at which and the terms and conditions upon which we may redeem the debt securities;

​

•

any obligation we have to redeem or purchase the debt securities pursuant to any sinking fund or analogous provisions or at the option of a holder of debt securities and the period or periods within which, the price or prices at which and in the terms and conditions upon which securities of the series shall be redeemed or purchased, in whole or in part, pursuant to such obligation;

​

•

the dates on which and the price or prices at which we will repurchase debt securities at the option of the holders of debt securities and other detailed terms and provisions of these repurchase obligations;

​

•

the denominations in which the debt securities will be issued, if other than denominations of $1,000 and any integral multiple thereof;

​

•

whether the debt securities will be issued in the form of certificated debt securities or global debt securities;

​

•

the portion of principal amount of the debt securities payable upon declaration of acceleration of the maturity date, if other than the principal amount;

​

•

the currency of denomination of the debt securities, which may be United States Dollars or any foreign currency, and if such currency of denomination is a composite currency, the agency or organization, if any, responsible for overseeing such composite currency;

​

•

the designation of the currency, currencies or currency units in which payment of principal of, premium and interest on the debt securities will be made;

​

•

if payments of principal of, premium or interest on the debt securities will be made in one or more currencies or currency units other than that or those in which the debt securities are denominated, the manner in which the exchange rate with respect to these payments will be determined;

​

•

the manner in which the amounts of payment of principal of, premium, if any, or interest on the debt securities will be determined, if these amounts may be determined by reference to an index based on a currency or currencies or by reference to a commodity, commodity index, stock exchange index or financial index;

​

•

any provisions relating to any security provided for the debt securities;

​

•

any addition to, deletion of or change in the Events of Default described in this prospectus or in the indenture with respect to the debt securities and any change in the acceleration provisions described in this prospectus or in the indenture with respect to the debt securities;

​

•

any addition to, deletion of or change in the covenants described in this prospectus or in the indenture with respect to the debt securities;

​

•

any depositaries, interest rate calculation agents, exchange rate calculation agents or other agents with respect to the debt securities;

​

•

the provisions, if any, relating to conversion or exchange of any debt securities of such series, including if applicable, the conversion or exchange price and period, provisions as to whether conversion or exchange will be mandatory, the events requiring an adjustment of the conversion or exchange price and provisions affecting conversion or exchange;

​

•

any other terms of the debt securities, which may supplement, modify or delete any provision of the indenture as it applies to that series, including any terms that may be required under applicable law or regulations or advisable in connection with the marketing of the securities; and

​

•

whether any of our direct or indirect subsidiaries will guarantee the debt securities of that series, including the terms of subordination, if any, of such guarantees. (Section 2.2)

​

We may issue debt securities that provide for an amount less than their stated principal amount to be due and payable upon declaration of acceleration of their maturity pursuant to the terms of the indenture. We will provide you with information on the U.S. federal income tax considerations and other special considerations applicable to any of these debt securities in the applicable prospectus supplement.

If we denominate the purchase price of any of the debt securities in a foreign currency or currencies or a foreign currency unit or units, or if the principal of and any premium and interest on any series of debt

securities is payable in a foreign currency or currencies or a foreign currency unit or units, we will provide you with information on the restrictions, elections, general tax considerations, specific terms and other information with respect to that issue of debt securities and such foreign currency or currencies or foreign currency unit or units in the applicable prospectus supplement.

Transfer and Exchange

Each debt security will be represented by either one or more global securities registered in the name of The Depository Trust Company, or the Depositary, or a nominee of the Depositary (we will refer to any debt security represented by a global debt security as a "book-entry debt security"), or a certificate issued in definitive registered form (we will refer to any debt security represented by a certificated security as a "certificated debt security") as set forth in the applicable prospectus supplement. Except as set forth under the heading "Global Debt Securities and Book-Entry System" below, book-entry debt securities will not be issuable in certificated form.

Certificated Debt Securities. You may transfer or exchange certificated debt securities at any office we maintain for this purpose in accordance with the terms of the indenture. (Section 2.4) No service charge will be made for any transfer or exchange of certificated debt securities, but we may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection with a transfer or exchange. (Section 2.7)

You may effect the transfer of certificated debt securities and the right to receive the principal of, premium and interest on certificated debt securities only by surrendering the certificate representing those certificated debt securities and either reissuance by us or the trustee of the certificate to the new holder or the issuance by us or the trustee of a new certificate to the new holder.

Global Debt Securities and Book-Entry System. Each global debt security representing book-entry debt securities will be deposited with, or on behalf of, the Depositary, and registered in the name of the Depositary or a nominee of the Depositary. Please see "Global Securities."

Covenants

We will set forth in the applicable prospectus supplement any restrictive covenants applicable to any issue of debt securities. (Article IV)

No Protection in the Event of a Change of Control

Unless we state otherwise in the applicable prospectus supplement, the debt securities will not contain any provisions which may afford holders of the debt securities protection in the event we have a change in control or in the event of a highly leveraged transaction (whether or not such transaction results in a change in control) which could adversely affect holders of debt securities.

Consolidation, Merger and Sale of Assets

We may not consolidate with or merge with or into, or convey, transfer or lease all or substantially all of our properties and assets to any person (a "successor person") unless:

•

we are the surviving entity or the successor person (if other than Deep Fission) is a corporation, partnership, trust or other entity organized and validly existing under the laws of any U.S. domestic jurisdiction and expressly assumes our obligations on the debt securities and under the indenture; and

​

•

immediately after giving effect to the transaction, no Default or Event of Default shall have occurred and be continuing.

​

Notwithstanding the above, any of our subsidiaries may consolidate with, merge into or transfer all or part of its properties to us. (Section 5.1)

Events of Default

"Event of Default" means with respect to any series of debt securities, any of the following:

•

default in the payment of any interest upon any debt security of that series when it becomes due and payable, and continuance of such default for a period of 30 days (unless the entire amount of the payment is deposited by us with the trustee or with a paying agent prior to the expiration of the 30-day period);

​

•

default in the payment of principal of any security of that series at its maturity;

​

•

default in the performance or breach of any other covenant or warranty by us in the indenture (other than a covenant or warranty that has been included in the indenture solely for the benefit of a series of debt securities other than that series), which default continues uncured for a period of 60 days after we receive written notice from the trustee or Deep Fission and the trustee receive written notice from the holders of not less than 25% in principal amount of the outstanding debt securities of that series as provided in the indenture;

​

•

certain voluntary or involuntary events of bankruptcy, insolvency or reorganization of Deep Fission;

​

•

any other Event of Default provided with respect to debt securities of that series that is described in the applicable prospectus supplement. (Section 6.1)

​

No Event of Default with respect to a particular series of debt securities (except as to certain events of bankruptcy, insolvency or reorganization) necessarily constitutes an Event of Default with respect to any other series of debt securities. (Section 6.1) The occurrence of certain Events of Default or an acceleration under the indenture may constitute an event of default under certain indebtedness of ours or our subsidiaries outstanding from time to time.

We will provide the trustee written notice of any Default or Event of Default within 30 days of becoming aware of the occurrence of such Default or Event of Default, which notice will describe in reasonable detail the status of such Default or Event of Default and what action we are taking or propose to take in respect thereof. (Section 6.1)

If an Event of Default with respect to debt securities of any series at the time outstanding occurs and is continuing, then the trustee or the holders of not less than 25% in principal amount of the outstanding debt securities of that series may, by a notice in writing to us (and to the trustee if given by the holders), declare to be due and payable immediately the principal of (or, if the debt securities of that series are discount securities, that portion of the principal amount as may be specified in the terms of that series) and accrued and unpaid interest, if any, on all debt securities of that series. In the case of an Event of Default resulting from certain events of bankruptcy, insolvency or reorganization, the principal (or such specified amount) of and accrued and unpaid interest, if any, on all outstanding debt securities will become and be immediately due and payable without any declaration or other act on the part of the trustee or any holder of outstanding debt securities. At any time after a declaration of acceleration with respect to debt securities of any series has been made, but before a judgment or decree for payment of the money due has been obtained by the trustee, the holders of a majority in principal amount of the outstanding debt securities of that series may rescind and annul the acceleration if all Events of Default, other than the non-payment of accelerated principal and interest, if any, with respect to debt securities of that series, have been cured or waived as provided in the indenture. (Section 6.2) We refer you to the prospectus supplement relating to any series of debt securities that are discount securities for the particular provisions relating to acceleration of a portion of the principal amount of such discount securities upon the occurrence of an Event of Default.

The indenture provides that the trustee may refuse to perform any duty or exercise any of its rights or powers under the indenture unless the trustee receives indemnity satisfactory to it against any cost, liability or expense which might be incurred by it in performing such duty or exercising such right or power. (Section 7.1(e)) Subject to certain rights of the trustee, the holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any trust or power conferred on the trustee with respect to the debt securities of that series. (Section 6.12)

No holder of any debt security of any series will have any right to institute any proceeding, judicial or otherwise, with respect to the indenture or for the appointment of a receiver or trustee, or for any remedy under the indenture, unless:

•

that holder has previously given to the trustee written notice of a continuing Event of Default with respect to debt securities of that series; and

​

•

the holders of not less than 25% in principal amount of the outstanding debt securities of that series have made written request, and offered indemnity or security satisfactory to the trustee, to the trustee to institute the proceeding as trustee, and the trustee has not received from the holders of not less than a majority in principal amount of the outstanding debt securities of that series a direction inconsistent with that request and has failed to institute the proceeding within 60 days. (Section 6.7)

​

Notwithstanding any other provision in the indenture, the holder of any debt security will have an absolute and unconditional right to receive payment of the principal of, premium and any interest on that debt security on or after the due dates expressed in that debt security and to institute suit for the enforcement of payment. (Section 6.8)

The indenture requires us, within 120 days after the end of our fiscal year, to furnish to the trustee a statement as to compliance with the indenture. (Section 4.3) If a Default or Event of Default occurs and is continuing with respect to the securities of any series and if it is known to a responsible officer of the trustee, the trustee shall mail to each holder of the securities of that series notice of a Default or Event of Default within 90 days after it occurs or, if later, after a responsible officer of the trustee has knowledge of such Default or Event of Default. The indenture provides that the trustee may withhold notice to the holders of debt securities of any series of any Default or Event of Default (except in payment on any debt securities of that series) with respect to debt securities of that series if the trustee determines in good faith that withholding notice is in the interest of the holders of those debt securities. (Section 7.5)

Modification and Waiver

We and the trustee may modify, amend or supplement the indenture or the debt securities of any series without the consent of any holder of any debt security:

•

to cure any ambiguity, defect or inconsistency;

​

•

to comply with covenants in the indenture described above under the heading "Consolidation, Merger and Sale of Assets";

​

•

to provide for uncertificated securities in addition to or in place of certificated securities;

​

•

to add guarantees with respect to debt securities of any series or secure debt securities of any series;

​

•

to surrender any of our rights or powers under the indenture;

​

•

to add covenants or events of default for the benefit of the holders of debt securities of any series;

​

•

to comply with the applicable procedures of the applicable depositary;

​

•

to make any change that does not adversely affect the rights of any holder of debt securities;

​

•

to provide for the issuance of and establish the form and terms and conditions of debt securities of any series as permitted by the indenture;

​

•

to effect the appointment of a successor trustee with respect to the debt securities of any series and to add to or change any of the provisions of the indenture to provide for or facilitate administration by more than one trustee; or

​

•

to comply with requirements of the SEC in order to effect or maintain the qualification of the indenture under the Trust Indenture Act. (Section 9.1)

​

We may also modify and amend the indenture with the consent of the holders of at least a majority in principal amount of the outstanding debt securities of each series affected by the modifications or amendments. We may not make any modification or amendment without the consent of the holders of each affected debt security then outstanding if that amendment will:

•

reduce the amount of debt securities whose holders must consent to an amendment, supplement or waiver;

​

•

reduce the rate of or extend the time for payment of interest (including default interest) on any debt security;

​

•

reduce the principal of or premium on or change the fixed maturity of any debt security or reduce the amount of, or postpone the date fixed for, the payment of any sinking fund or analogous obligation with respect to any series of debt securities;

​

•

reduce the principal amount of discount securities payable upon acceleration of maturity;

​

•

waive a default in the payment of the principal of, premium or interest on any debt security (except a rescission of acceleration of the debt securities of any series by the holders of at least a majority in aggregate principal amount of the then outstanding debt securities of that series and a waiver of the payment default that resulted from such acceleration);

​

•

make the principal of or premium or interest on any debt security payable in currency other than that stated in the debt security;

​

•

make any change to certain provisions of the indenture relating to, among other things, the right of holders of debt securities to receive payment of the principal of, premium and interest on those debt securities and to institute suit for the enforcement of any such payment and to waivers or amendments; or

​

•

waive a redemption payment with respect to any debt security. (Section 9.3)

​

Except for certain specified provisions, the holders of at least a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all debt securities of that series waive our compliance with provisions of the indenture. (Section 9.2) The holders of a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all the debt securities of such series waive any past default under the indenture with respect to that series and its consequences, except a default in the payment of the principal of, premium or any interest on any debt security of that series; provided, however, that the holders of a majority in principal amount of the outstanding debt securities of any series may rescind an acceleration and its consequences, including any related payment default that resulted from the acceleration. (Section 6.13)

Defeasance of Debt Securities and Certain Covenants in Certain Circumstances

Legal Defeasance. The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, we may be discharged from any and all obligations in respect of the debt securities of any series (subject to certain exceptions). We will be so discharged upon the irrevocable deposit with the trustee, in trust, of money and/or U.S. government obligations or, in the case of debt securities denominated in a single currency other than U.S. Dollars, government obligations of the government that issued or caused to be issued such currency, that, through the payment of interest and principal in accordance with their terms, will provide money or U.S. government obligations in an amount sufficient in the opinion of a nationally recognized firm of independent public accountants or investment bank to pay and discharge each installment of principal, premium and interest on and any mandatory sinking fund payments in respect of the debt securities of that series on the stated maturity of those payments in accordance with the terms of the indenture and those debt securities.

This discharge may occur only if, among other things, we have delivered to the trustee an opinion of counsel stating that we have received from, or there has been published by, the United States Internal Revenue Service a ruling or, since the date of execution of the indenture, there has been a change in the applicable United States federal income tax law, in either case to the effect that, and based thereon such opinion shall confirm that, the holders of the debt securities of that series will not recognize income, gain or loss for United States federal income tax purposes as a result of the deposit, defeasance and discharge and will be subject to United States federal income tax on the same amounts and in the same manner and at the same times as would have been the case if the deposit, defeasance and discharge had not occurred. (Section 8.3)

Defeasance of Certain Covenants. The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, upon compliance with certain conditions:

•

we may omit to comply with the covenant described under the heading "Consolidation, Merger and Sale of Assets" and certain other covenants set forth in the indenture, as well as any additional covenants which may be set forth in the applicable prospectus supplement; and

​

•

any omission to comply with those covenants will not constitute a Default or an Event of Default with respect to the debt securities of that series ("covenant defeasance").

​

The conditions include:

•

depositing with the trustee money and/or U.S. government obligations or, in the case of debt securities denominated in a single currency other than U.S. Dollars, government obligations of the government that issued or caused to be issued such currency, that, through the payment of interest and principal in accordance with their terms, will provide money in an amount sufficient in the opinion of a nationally recognized firm of independent public accountants or investment bank to pay and discharge each installment of principal of, premium and interest on and any mandatory sinking fund payments in respect of the debt securities of that series on the stated maturity of those payments in accordance with the terms of the indenture and those debt securities; and

​

•

delivering to the trustee an opinion of counsel to the effect that the holders of the debt securities of that series will not recognize income, gain or loss for United States federal income tax purposes as a result of the deposit and related covenant defeasance and will be subject to United States federal income tax on the same amounts and in the same manner and at the same times as would have been the case if the deposit and related covenant defeasance had not occurred. (Section 8.4)

​

No Personal Liability of Directors, Officers, Employees or Securityholders

None of our past, present or future directors, officers, employees or securityholders, as such, will have any liability for any of our obligations under the debt securities or the indenture or for any claim based on, or in respect or by reason of, such obligations or their creation. By accepting a debt security, each holder waives and releases all such liability. This waiver and release is part of the consideration for the issue of the debt securities. However, this waiver and release may not be effective to waive liabilities under U.S. federal securities laws, and it is the view of the SEC that such a waiver is against public policy.

Governing Law

The indenture and the debt securities, including any claim or controversy arising out of or relating to the indenture or the securities, will be governed by the laws of the State of New York.

The indenture will provide that we, the trustee and the holders of the debt securities (by their acceptance of the debt securities) irrevocably waive, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to the indenture, the debt securities or the transactions contemplated thereby.

The indenture will provide that any legal suit, action or proceeding arising out of or based upon the indenture or the transactions contemplated thereby may be instituted in the federal courts of the United States of America located in the City of New York or the courts of the State of New York in each case located in the City of New York, and we, the trustee and the holder of the debt securities (by their acceptance of the debt securities) irrevocably submit to the non-exclusive jurisdiction of such courts in any such suit, action or proceeding. The indenture will further provide that service of any process, summons, notice or document by mail (to the extent allowed under any applicable statute or rule of court) to such party's address set forth in the indenture will be effective service of process for any suit, action or other proceeding brought in any such court. The indenture will further provide that we, the trustee and the holders of the debt securities (by their acceptance of the debt securities) irrevocably and unconditionally waive any objection to the laying of venue of any suit, action or other proceeding in the courts specified above and irrevocably and unconditionally waive and agree not to plead or claim any such suit, action or other proceeding has been brought in an inconvenient forum. (Section 10.10)

DESCRIPTION OF WARRANTS

We may issue warrants for the purchase of shares of our Common Stock or preferred stock or of debt securities. We may issue warrants independently or together with other securities, and the warrants may be attached to or separate from any offered securities. Each series of warrants will be issued under a separate warrant agreement to be entered into between us and the investors or a warrant agent. The following summary of material provisions of the warrants and warrant agreements is subject to, and qualified in their entirety by reference to, all the provisions of the warrant agreement and warrant certificate applicable to a particular series of warrants. The terms of any warrants offered under a prospectus supplement may differ from the terms described below. We urge you to read the applicable prospectus supplement and any related free writing prospectus, as well as the complete warrant agreements and warrant certificates that contain the terms of the warrants.

The particular terms of any issue of warrants will be described in the prospectus supplement relating to the issue. Those terms may include:

•

the number of shares of Common Stock or preferred stock purchasable upon the exercise of warrants to purchase such shares and the price at which such number of shares may be purchased upon such exercise;

​

•

the designation, stated value and terms (including, without limitation, liquidation, dividend, conversion and voting rights) of the series of preferred stock purchasable upon exercise of warrants to purchase preferred stock;

​

•

the principal amount of debt securities that may be purchased upon exercise of a debt warrant and the exercise price for the warrants, which may be payable in cash, securities or other property;

​

•

the date, if any, on and after which the warrants and the related debt securities, preferred stock or Common Stock will be separately transferable;

​

•

the terms of any rights to redeem or call the warrants;

​

•

the date on which the right to exercise the warrants will commence and the date on which the right will expire;

​

•

certain U.S. federal income tax consequences applicable to the warrants; and

​

•

any additional terms of the warrants, including terms, procedures, and limitations relating to the exchange, exercise and settlement of the warrants.

​

Holders of equity warrants will not be entitled to:

•

vote, consent or receive dividends;

​

•

receive notice as stockholders with respect to any meeting of stockholders for the election of our directors or any other matter; or

​

•

exercise any rights as stockholders of Deep Fission.

​

Each warrant will entitle its holder to purchase the principal amount of debt securities or the number of shares of preferred stock or Common Stock at the exercise price set forth in, or calculable as set forth in, the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to the specified time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

A holder of warrant certificates may exchange them for new warrant certificates of different denominations, present them for registration of transfer and exercise them at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement. Until any warrants to purchase debt securities are exercised, the holder of the warrants will not have any rights of holders of the debt securities that can be purchased upon exercise, including any rights to receive payments of principal, premium or interest on the underlying debt securities or to enforce covenants in the applicable indenture. Until any warrants to purchase Common Stock or preferred stock are exercised, the holders of the warrants

DESCRIPTION OF RIGHTS

The following description, together with the additional information we include in any applicable prospectus supplements, summarizes the material terms and provisions of the rights that we may offer under this prospectus, which consist of rights to purchase our Common Stock, preferred stock and/or debt securities in one or more series. Rights may be offered independently or together with our Common Stock, preferred stock, debt securities and/or warrants offered by any prospectus supplement and may be attached to or separate from those securities. While the terms we have summarized below will generally apply to any future rights we may offer pursuant to this prospectus, we will describe the particular terms of any rights that we may offer in more detail in the applicable prospectus supplements. The terms of any rights we offer under a prospectus supplement may differ from the terms we describe below.

General

The applicable prospectus supplements relating to any rights that we offer will include specific terms of any offering of rights for which this prospectus is being delivered, including the following, to the extent applicable:

•

the date for determining the persons entitled to participate in the rights distribution;

​

•

the price, if any, per right;

​

•

the exercise price payable for each share of Common Stock, share of preferred stock or debt security upon the exercise of the rights;

​

•

the number of rights issued or to be issued to each holder;

​

•

the number and terms of the shares of Common Stock, shares of preferred stock or debt securities that may be purchased per each right;

​

•

the extent to which the rights are transferable;

​

•

any other terms of the rights, including the terms, procedures and limitations relating to the exchange and exercise of the rights;

​

•

the respective dates on which the holder's ability to exercise the rights will commence and will expire;

​

•

the number of rights outstanding, if any;

​

•

a discussion of certain U.S. federal income tax considerations applicable to the rights;

​

•

the extent to which the rights may include an over-subscription privilege with respect to unsubscribed securities; and

​

•

if applicable, the material terms of any standby underwriting or purchase arrangement entered into by us in connection with the offering of such rights.

​

The description in the applicable prospectus supplements of any rights that we may offer will not necessarily be complete and will be qualified in its entirety by reference to the applicable rights agreement and/or rights certificate, which will be filed with the SEC in connection therewith.

Outstanding Rights

We have no outstanding rights.

DESCRIPTION OF UNITS

We may issue units consisting of any combination of the other types of securities offered under this prospectus in one or more series. We may evidence each series of units by unit certificates that we will issue under a separate agreement. We may enter into unit agreements with a unit agent. Each unit agent will be a bank or trust company that we select. We will indicate the name and address of the unit agent in the applicable prospectus supplement relating to a particular series of units.

The following description, together with the additional information included in any applicable prospectus supplement, summarizes the general features of the units that we may offer under this prospectus. You should read any prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the series of units being offered, as well as the complete unit agreements that contain the terms of the units. Specific unit agreements will contain additional important terms and provisions and we will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from another report that we file with the SEC, the form of each unit agreement relating to units offered under this prospectus.

If we offer any units, certain terms of that series of units will be described in the applicable prospectus supplement, including, without limitation, the following, as applicable:

•

the title of the series of units;

​

•

identification and description of the separate constituent securities comprising the units;

​

•

the price or prices at which the units will be issued;

​

•

the date, if any, on and after which the constituent securities comprising the units will be separately transferable;

​

•

a discussion of certain U.S. federal income tax considerations applicable to the units; and

​

•

any other terms of the units and their constituent securities.

​

GLOBAL SECURITIES

Book-Entry, Delivery and Form

Unless we indicate differently in any applicable prospectus supplement or free writing prospectus, the securities initially will be issued in book-entry form and represented by one or more global notes or global securities, or, collectively, global securities. The global securities will be deposited with, or on behalf of, The Depository Trust Company, New York, New York, as depositary, or DTC, and registered in the name of Cede & Co., the nominee of DTC. Unless and until it is exchanged for individual certificates evidencing securities under the limited circumstances described below, a global security may not be transferred except as a whole by the depositary to its nominee or by the nominee to the depositary, or by the depositary or its nominee to a successor depositary or to a nominee of the successor depositary.

DTC has advised us that it is:

•

a limited-purpose trust company organized under the New York Banking Law;

​

•

a "banking organization" within the meaning of the New York Banking Law;

​

•

a member of the Federal Reserve System;

​

•

a "clearing corporation" within the meaning of the New York Uniform Commercial Code; and

​

•

a "clearing agency" registered pursuant to the provisions of Section 17A of the Exchange Act.

​

DTC holds securities that its participants deposit with DTC. DTC also facilitates the settlement among its participants of securities transactions, such as transfers and pledges, in deposited securities through electronic computerized book-entry changes in participants' accounts, thereby eliminating the need for physical movement of securities certificates. "Direct participants" in DTC include securities brokers and dealers, including underwriters, banks, trust companies, clearing corporations and other organizations. DTC is a wholly owned subsidiary of The Depository Trust & Clearing Corporation, or DTCC. DTCC is the holding company for DTC, National Securities Clearing Corporation and Fixed Income Clearing Corporation, all of which are registered clearing agencies. DTCC is owned by the users of its regulated subsidiaries. Access to the DTC system is also available to others, which we sometimes refer to as indirect participants, that clear through or maintain a custodial relationship with a direct participant, either directly or indirectly. The rules applicable to DTC and its participants are on file with the SEC.

Purchases of securities under the DTC system must be made by or through direct participants, which will receive a credit for the securities on DTC's records. The ownership interest of the actual purchaser of a security, which we sometimes refer to as a beneficial owner, is in turn recorded on the direct and indirect participants' records. Beneficial owners of securities will not receive written confirmation from DTC of their purchases. However, beneficial owners are expected to receive written confirmations providing details of their transactions, as well as periodic statements of their holdings, from the direct or indirect participants through which they purchased securities. Transfers of ownership interests in global securities are to be accomplished by entries made on the books of participants acting on behalf of beneficial owners. Beneficial owners will not receive certificates representing their ownership interests in the global securities, except under the limited circumstances described below.

To facilitate subsequent transfers, all global securities deposited by direct participants with DTC will be registered in the name of DTC's partnership nominee, Cede & Co., or such other name as may be requested by an authorized representative of DTC. The deposit of securities with DTC and their registration in the name of Cede & Co. or such other nominee will not change the beneficial ownership of the securities. DTC has no knowledge of the actual beneficial owners of the securities. DTC's records reflect only the identity of the direct participants to whose accounts the securities are credited, which may or may not be the beneficial owners. The participants are responsible for keeping account of their holdings on behalf of their customers.

So long as the securities are in book-entry form, you will receive payments and may transfer securities only through the facilities of the depositary and its direct and indirect participants. We will maintain an office or agency in the location specified in the prospectus supplement for the applicable securities, where notices and demands in respect of the securities and the indenture may be delivered to us and where certificated securities may be surrendered for payment, registration of transfer or exchange.

Conveyance of notices and other communications by DTC to direct participants, by direct participants to indirect participants and by direct participants and indirect participants to beneficial owners will be governed by arrangements among them, subject to any legal requirements in effect from time to time.

Redemption notices will be sent to DTC. If less than all of the securities of a particular series are being redeemed, DTC's practice is to determine by lot the amount of the interest of each direct participant in the securities of such series to be redeemed.

Neither DTC nor Cede & Co. (or such other DTC nominee) will consent or vote with respect to the securities. Under its usual procedures, DTC will mail an omnibus proxy to us as soon as possible after the record date. The omnibus proxy assigns the consenting or voting rights of Cede & Co. to those direct participants to whose accounts the securities of such series are credited on the record date, identified in a listing attached to the omnibus proxy.

So long as securities are in book-entry form, we will make payments on those securities to the depositary or its nominee, as the registered owner of such securities, by wire transfer of immediately available funds. If securities are issued in definitive certificated form under the limited circumstances described below and unless if otherwise provided in the description of the applicable securities herein or in the applicable prospectus supplement, we will have the option of making payments by check mailed to the addresses of the persons entitled to payment or by wire transfer to bank accounts in the United States designated in writing to the applicable trustee or other designated party at least 15 days before the applicable payment date by the persons entitled to payment, unless a shorter period is satisfactory to the applicable trustee or other designated party.

Redemption proceeds, distributions and dividend payments on the securities will be made to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC. DTC's practice is to credit direct participants' accounts upon DTC's receipt of funds and corresponding detail information from us on the payment date in accordance with their respective holdings shown on DTC records. Payments by participants to beneficial owners will be governed by standing instructions and customary practices, as is the case with securities held for the account of customers in bearer form or registered in "street name." Those payments will be the responsibility of participants and not of DTC or us, subject to any statutory or regulatory requirements in effect from time to time. Payment of redemption proceeds, distributions and dividend payments to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC, is our responsibility, disbursement of payments to direct participants is the responsibility of DTC, and disbursement of payments to the beneficial owners is the responsibility of direct and indirect participants.

Except under the limited circumstances described below, purchasers of securities will not be entitled to have securities registered in their names and will not receive physical delivery of securities. Accordingly, each beneficial owner must rely on the procedures of DTC and its participants to exercise any rights under the securities and the indenture.

The laws of some jurisdictions may require that some purchasers of securities take physical delivery of securities in definitive form. Those laws may impair the ability to transfer or pledge beneficial interests in securities.

DTC may discontinue providing its services as securities depositary with respect to the securities at any time by giving reasonable notice to us. Under such circumstances, in the event that a successor depositary is not obtained, securities certificates are required to be printed and delivered.

As noted above, beneficial owners of a particular series of securities generally will not receive certificates representing their ownership interests in those securities. However, if:

•

DTC notifies us that it is unwilling or unable to continue as a depositary for the global security or securities representing such series of securities or if DTC ceases to be a clearing agency registered under the Exchange Act at a time when it is required to be registered and a successor depositary is not appointed within 90 days of the notification to us or of our becoming aware of DTC's ceasing to be so registered, as the case may be;

​

•

we determine, in our sole discretion, not to have such securities represented by one or more global securities; or

​

•

an Event of Default has occurred and is continuing with respect to such series of securities,

​

we will prepare and deliver certificates for such securities in exchange for beneficial interests in the global securities. Any beneficial interest in a global security that is exchangeable under the circumstances described in the preceding sentence will be exchangeable for securities in definitive certificated form registered in the names that the depositary directs. It is expected that these directions will be based upon directions received by the depositary from its participants with respect to ownership of beneficial interests in the global securities.

Euroclear and Clearstream

If so provided in the applicable prospectus supplement, you may hold interests in a global security through Clearstream Banking S.A., which we refer to as "Clearstream," or Euroclear Bank S.A./N.V., as operator of the Euroclear System, which we refer to as "Euroclear," either directly if you are a participant in Clearstream or Euroclear or indirectly through organizations which are participants in Clearstream or Euroclear. Clearstream and Euroclear will hold interests on behalf of their respective participants through customers' securities accounts in the names of Clearstream and Euroclear, respectively, on the books of their respective U.S. depositaries, which in turn will hold such interests in customers' securities accounts in such depositaries' names on DTC's books.

Clearstream and Euroclear are securities clearance systems in Europe. Clearstream and Euroclear hold securities for their respective participating organizations and facilitate the clearance and settlement of securities transactions between those participants through electronic book-entry changes in their accounts, thereby eliminating the need for physical movement of certificates.

Payments, deliveries, transfers, exchanges, notices and other matters relating to beneficial interests in global securities owned through Euroclear or Clearstream must comply with the rules and procedures of those systems. Transactions between participants in Euroclear or Clearstream, on one hand, and other participants in DTC, on the other hand, are also subject to DTC's rules and procedures.

Investors will be able to make and receive through Euroclear and Clearstream payments, deliveries, transfers and other transactions involving any beneficial interests in global securities held through those systems only on days when those systems are open for business. Those systems may not be open for business on days when banks, brokers and other institutions are open for business in the United States.

Cross-market transfers between participants in DTC, on the one hand, and participants in Euroclear or Clearstream, on the other hand, will be effected through DTC in accordance with DTC's rules on behalf of Euroclear or Clearstream, as the case may be, by their respective U.S. depositaries; however, such cross-market transactions will require delivery of instructions to Euroclear or Clearstream, as the case may be, by the counterparty in such system in accordance with the rules and procedures and within the established deadlines (European time) of such system. Euroclear or Clearstream, as the case may be, will, if the transaction meets its settlement requirements, deliver instructions to its U.S. depositary to take action to effect final settlement on its behalf by delivering or receiving interests in the global securities through DTC, and making or receiving payment in accordance with normal procedures for same-day fund settlement. Participants in Euroclear or Clearstream may not deliver instructions directly to their respective U.S. depositaries.

Due to time zone differences, the securities accounts of a participant in Euroclear or Clearstream purchasing an interest in a global security from a direct participant in DTC will be credited, and any such crediting will be reported to the relevant participant in Euroclear or Clearstream, during the securities settlement processing day (which must be a business day for Euroclear or Clearstream) immediately following the settlement date of DTC. Cash received in Euroclear or Clearstream as a result of sales of interests in a global security by or through a participant in Euroclear or Clearstream to a direct participant in DTC will be received with value on the settlement date of DTC but will be available in the relevant Euroclear or Clearstream cash account only as of the business day for Euroclear or Clearstream following DTC's settlement date.

Other

The information in this section of this prospectus concerning DTC, Clearstream, Euroclear and their respective book-entry systems has been obtained from sources that we believe to be reliable, but we do not

PLAN OF DISTRIBUTION

We may sell the securities from time to time pursuant to underwritten public offerings, negotiated transactions, block trades, any method that is deemed an "at the market offering" as defined in Rule 415(a)(4) under the Securities Act, or a combination of these methods or through underwriters or dealers, through agents and/or directly to one or more purchasers. The securities may be distributed from time to time in one or more transactions:

•

at a fixed price or prices, which may be changed;

​

•

at market prices prevailing at the time of sale;

​

•

at prices related to such prevailing market prices; or

​

•

at negotiated prices.

​

Each time that we sell securities covered by this prospectus, we will provide a prospectus supplement or supplements that will describe the method of distribution and set forth the terms and conditions of the offering of such securities, including the offering price of the securities and the proceeds to us, if applicable.

Offers to purchase the securities being offered by this prospectus may be solicited directly. Agents may also be designated to solicit offers to purchase the securities from time to time. Any agent involved in the offer or sale of our securities will be identified in a prospectus supplement.

If a dealer is utilized in the sale of the securities being offered by this prospectus, the securities will be sold to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale.

If an underwriter is utilized in the sale of the securities being offered by this prospectus, an underwriting agreement will be executed with the underwriter at the time of sale and the name of any underwriter will be provided in the prospectus supplement that the underwriter will use to make resales of the securities to the public. In connection with the sale of the securities, we or the purchasers of securities for whom the underwriter may act as agent, may compensate the underwriter in the form of underwriting discounts or commissions. The underwriter may sell the securities to or through dealers, and those dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for which they may act as agent. Unless otherwise indicated in a prospectus supplement, an agent will be acting on a best efforts basis and a dealer will purchase securities as a principal, and may then resell the securities at varying prices to be determined by the dealer.

Any compensation paid to underwriters, dealers or agents in connection with the offering of the securities, and any discounts, concessions or commissions allowed by underwriters to participating dealers will be provided in the applicable prospectus supplement. Underwriters, dealers and agents participating in the distribution of the securities may be deemed to be underwriters within the meaning of the Securities Act, and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions. We may enter into agreements to indemnify underwriters, dealers and agents against civil liabilities, including liabilities under the Securities Act, or to contribute to payments they may be required to make in respect thereof and to reimburse those persons for certain expenses.

Any Common Stock will be listed on Nasdaq, but any other securities may or may not be listed on a national securities exchange. To facilitate the offering of securities, certain persons participating in the offering may engage in transactions that stabilize, maintain or otherwise affect the price of the securities. This may include over-allotments or short sales of the securities, which involve the sale by persons participating in the offering of more securities than were sold to them. In these circumstances, these persons would cover such over-allotments or short positions by making purchases in the open market or by exercising their over-allotment option, if any. In addition, these persons may stabilize or maintain the price of the securities by bidding for or purchasing securities in the open market or by imposing penalty bids, whereby selling concessions allowed to dealers participating in the offering may be reclaimed if securities sold by them are repurchased in connection with stabilization transactions. The effect of these transactions may be to stabilize

or maintain the market price of the securities at a level above that which might otherwise prevail in the open market. These transactions may be discontinued at any time.

We may engage in at the market offerings into an existing trading market in accordance with Rule 415(a)(4) under the Securities Act. In addition, we may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement so indicates, in connection with those derivatives, the third parties may sell securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by us or borrowed from us or others to settle those sales or to close out any related open borrowings of stock, and may use securities received from us in settlement of those derivatives to close out any related open borrowings of stock. The third party in such sale transactions will be an underwriter and, if not identified in this prospectus, will be named in the applicable prospectus supplement (or a post-effective amendment). In addition, we may otherwise loan or pledge securities to a financial institution or other third party that in turn may sell the securities short using this prospectus and an applicable prospectus supplement. Such financial institution or other third party may transfer its economic short position to investors in our securities or in connection with a concurrent offering of other securities.

The specific terms of any lock-up provisions in respect of any given offering will be described in the applicable prospectus supplement.

The underwriters, dealers and agents may engage in transactions with us, or perform services for us, in the ordinary course of business for which they receive compensation.

LEGAL MATTERS

Orrick, Herrington & Sutcliffe LLP, Boston, Massachusetts, will pass upon certain legal matters relating to the issuance and sale of the securities offered hereby on behalf of Deep Fission, Inc. Additional legal matters may be passed upon for us or any underwriters, dealers or agents, by counsel that we will name in the applicable prospectus supplement.

EXPERTS

The audited financial statements incorporated by reference in this prospectus and elsewhere in the registration statement have been so incorporated by reference in reliance upon the report of Grant Thornton LLP, independent registered public accountants, upon the authority of said firm as experts in accounting and auditing.

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. Other Expenses of Issuance and Distribution.

The following is an estimate of the expenses (all of which are to be paid by the registrant) that we may incur in connection with the securities being registered hereby.

​

*

These fees are calculated based on the securities offered and the number of issuances and accordingly cannot be defined at this time.

​

Item 15. Indemnification of Directors and Officers.

Subsection (a) of Section 145 of the DGCL ("Section 145"), empowers a corporation to indemnify any person who was or is a party or who is threatened to be made a party to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of the corporation) by reason of the fact that the person is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorneys' fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by the person in connection with such action, suit or proceeding if the person acted in good faith and in a manner the person reasonably believed to be in or not opposed to the best interests of the corporation, and, with respect to any criminal action or proceeding, had no reasonable cause to believe the person's conduct was unlawful.

Subsection (b) of Section 145 empowers a corporation to indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action or suit by or in the right of the corporation to procure a judgment in its favor by reason of the fact that the person acted in any of the capacities set forth above, against expenses (including attorneys' fees) actually and reasonably incurred by the person in connection with the defense or settlement of such action or suit if the person acted in good faith and in a manner the person reasonably believed to be in or not opposed to the best interests of the corporation, except that no indemnification shall be made in respect of any claim, issue or matter as to which such person shall have been adjudged to be liable to the corporation unless and only to the extent that the Court of Chancery or the court in which such action or suit was brought shall determine upon application that, despite the adjudication of liability but in view of all the circumstances of the case, such person is fairly and reasonably entitled to indemnity for such expenses which the Court of Chancery or such other court shall deem proper.

Section 145 further provides that to the extent a director or officer of a corporation has been successful on the merits or otherwise in the defense of any action, suit or proceeding referred to in subsections (a) and (b) of Section 145, or in defense of any claim, issue or matter therein, such person shall be indemnified

against expenses (including attorneys' fees) actually and reasonably incurred by such person in connection therewith; that indemnification provided for by Section 145 shall not be deemed exclusive of any other rights to which the indemnified party may be entitled; and the indemnification provided for by Section 145 shall, unless otherwise provided when authorized or ratified, continue as to a person who has ceased to be a director, officer, employee or agent and shall inure to the benefit of such person's heirs, executors and administrators. Section 145 also empowers the corporation to purchase and maintain insurance on behalf of any person who is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise against any liability asserted against such person and incurred by such person in any such capacity, or arising out of his status as such, whether or not the corporation would have the power to indemnify such person against such liabilities under Section 145.

Section 102(b)(7) of the DGCL provides that a corporation's certificate of incorporation may contain a provision eliminating or limiting the personal liability of a director to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, provided that such provision shall not eliminate or limit the liability of a director (i) for any breach of the director's duty of loyalty to the corporation or its stockholders, (ii) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (iii) under Section 174 of the DGCL, or (iv) for any transaction from which the director derived an improper personal benefit.

Any underwriting agreement or distribution agreement that the registrant enters into with any underwriters or agents involved in the offering or sale of any securities registered hereby may require such underwriters or dealers to indemnify the registrant, some or all of its directors and officers and its controlling persons, if any, for specified liabilities, which may include liabilities under the Securities Act of 1933, as amended.

We have entered into agreements with each of our directors and executive officers that provide for indemnification to the maximum extent permitted by law. In some cases, the provisions of these indemnification agreements may be broader than the specific indemnification provisions contained under the DGCL and any other applicable law.

Item 16. Exhibits.

​

*

To be filed by amendment or incorporated by reference in connection with the offering of the securities.

​

**

To be filed in accordance with the requirements of Section 305(b)(2) of the Trust Indenture Act of 1939 and Rule 5b-3 thereunder.

​

Item 17. Undertakings.

(a)

The undersigned registrant hereby undertakes:

​

(1)

To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

​

(i)

To include any prospectus required by Section 10(a)(3) of the Securities Act of 1933;

​

(ii)

To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the SEC pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20 percent change in the maximum aggregate offering price set forth in the "Calculation of Filing Fee Tables" in the effective registration statement; and

​

(iii)

To include any material information with respect to the plan of distribution not previously

​

disclosed in the registration statement or any material change to such information in this registration statement;

provided, however, that the undertakings set forth in paragraphs (a)(1)(i), (a)(1)(ii) and (a)(1)(iii) above do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the SEC by the registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is a part of the registration statement.

(2)

That, for the purpose of determining any liability under the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

​

(3)

To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

​

(4)

That, for the purpose of determining liability under the Securities Act of 1933 to any purchaser:

​

(i)

Each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

​

(ii)

Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5), or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii), or (x) for the purpose of providing the information required by section 10(a) of the Securities Act of 1933 shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

​

(5)

That, for the purpose of determining liability of the registrant under the Securities Act of 1933 to any purchaser in the initial distribution of the securities:

​

The undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i)

any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

​

(ii)

any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

​

(iii)

the portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

​

(iv)

any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

​

(b)

The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act of 1933, each filing of the registrant's annual report pursuant to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan's annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

​

(c)

Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions or otherwise, the registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

​

(d)

The undersigned registrant hereby undertakes to file an application for the purpose of determining the eligibility of the trustee to act under subsection (a) of Section 310 of the Trust Indenture Act (the "Act") in accordance with the rules and regulations prescribed by the SEC under Section 305(b)(2) of the Act.

​

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Santa Clara, State of California, on November 4, 2026.

DEEP FISSION, INC.

By:

/s/ Elizabeth Muller

​

​

Name: Elizabeth Muller
Title:  Chair, President and Chief Executive Officer

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints Elizabeth Muller and William (Mark) Schmitz, and each of them acting individually, as his or her true and lawful attorneys-in-fact and agents, with full power of each to act alone, with full powers of substitution and resubstitution in each of them, for him or her and in his or her name, place and stead, in any and all capacities, to sign the Registration Statement filed herewith and any and all amendments to said Registration Statement (including post-effective amendments and any related registration statements thereto filed pursuant to Rule 462 and otherwise), and file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, with full power of each to act alone, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully for all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or his or their substitutes, may lawfully do or cause to be done by virtue hereof. This power of attorney shall be governed by and construed with the laws of the State of Delaware and applicable federal securities laws.

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed by the following persons in the capacities and on the dates indicated: