DEEP FISSION, INC.

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LETTER FROM THE CEO AND CO-FOUNDER

Dear Fellow Shareholders,

We are excited to file our first Annual Report as a public company, and I wanted to share this letter to highlight some of the key priorities that are discussed in more detail elsewhere in this report.

Foremost, I believe the biggest barrier to nuclear energy isn’t new reactor technology; it’s time.

For decades, many in our industry have followed the same, tired playbook: design a reactor, show it works on paper, then try to figure out how to commercialize the design. Each step typically adds years and can cost hundreds of millions (or potentially even billions) of dollars, waiting until the final step to determine whether the technology is viable to generate and sell electricity. By that time, the commercial opportunity may have already passed.

I think there’s a better way. Deep Fission’s goal is to focus on commercial deployment from the start.

At Deep Fission, we’re not trying to invent a new type of reactor. The technology we are utilizing, pressurized water reactors (PWRs), has been deployed for decades in commercial power generation, and uses readily-available low-enriched uranium (LEU) fuel. As of 2025, there are 64 safely operating PWRs in the United States, generating about 12% of our nation’s electricity. Due to this legacy of continuous operation, criticality is not our primary technical proof point.

Our difference is our deployment model.

From the beginning, we have prioritized deployment over invention. Our Gravity Nuclear Reactor leverages existing capabilities developed in the oil, gas, and geothermal industries to deploy established PWR technology in a new way. This involves novel emplacement of PWRs in mile-deep boreholes underground, utilizing the rock itself to provide structural confinement and shielding, along with pressure from a mile-long column of water on top of the reactor in the borehole. This reduces the need for large surface infrastructure associated with conventional nuclear power plants, allowing us to streamline deployment of a technology we already understand.

As our business has begun to mature, we are now sharing our phased plan for commercial viability in the next three years.

In December 2025 we broke ground in Parsons, Kansas, in furtherance of participation in the Department of Energy’s (“DOE”) Reactor Pilot Program. We have already drilled our first data acquisition well to gather real-world data up to 6,000 feet deep. Next, we will demonstrate our ability to drill a commercial-scale borehole and safely deploy a prototype reactor. We’re aiming to complete this drilling, engineering, and emplacement validation phase in the coming months.

The balance of this year and into early 2027 will be focused on delivery of key components for full-system installation, including well casing, our reactor canister, and heat exchanger, as well as LEU fabrication and loading. Pending DOE authorization, we plan to demonstrate our system and apply for a commercial license in the first half of 2027, converting the same pilot reactor to commercial operation. We are targeting as early as that same year to seek high-volume commercial licensing for deployment of multiple boreholes and subsequently, at multiple sites.

Deep Fission is prioritizing validation of the hardest and most differentiated parts of our system, to reduce risk earlier and move more directly toward a commercial outcome. We are working closely with both the DOE and the Nuclear Regulatory Commission to align demonstration and licensing, aiming to move these efforts forward in parallel.

Our goal is to bring new nuclear capacity online faster and more predictably, on pace with modern infrastructure and AI-driven demand. Nuclear can help meet the need for more electricity, but only if we build it in a way that works in the real world. We are starting with planned sites in Kansas, Texas, and Utah, inviting people, partners, and the public to build with us.

We encourage you to read the rest of our Annual Report for additional information regarding our business, including our key priorities.

Sincerely,

Elizabeth Muller

Chair, President and Chief Executive Officer of Deep Fission, Inc.

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EXPLANATORY NOTE

Restatement Background

As previously announced in our Current Report on Form 8-K filed with the Securities and Exchange Commission (the “SEC”) on April 9, 2026, on April 9, 2026, the Audit Committee (the “Audit Committee”) of the board of directors, in consultation with management, concluded that the audited consolidated financial statements for the fiscal year ended December 31, 2024 and for the period from July 17, 2023 (inception) through December 31, 2023, and the unaudited condensed consolidated financial statements for the six month periods ended June 30, 2024 and 2025, and the three- and nine-month periods ended September 30, 2024 and 2025 of Deep Fission, Inc. (“Deep Fission,” the “Company,” “we,” “our,” or “us”) could no longer be relied upon as a result of material accounting errors identified by management subsequent to the issuance of the Company’s unaudited interim condensed consolidated financial statements as of and for the fiscal quarter ended September 30, 2025.

This Annual Report on Form 10-K for the fiscal year ended December 31, 2025 (this “Annual Report”) includes audited consolidated financial statements of the Company for the fiscal years ended December 31, 2025 and 2024. The consolidated financial statements for the year ended December 31, 2024 and the unaudited condensed consolidated financial information for the six-month periods ended June 30, 2024 and 2025, and the three- and nine-month periods ended September 30, 2024 and 2025 included in this Annual Report have been restated to reflect the correction of identified errors (the “Misstatements”) related to valuations of Simple Agreement for Future Equity (“SAFE Notes”) and stock-based compensation expense (the “Restatement”) (refer to Note 2. Restatement of Previously Issued Consolidated Financial Statements and Note 12. Quarterly Financial Data (Unaudited) to our financial statements included in Part II, Item 8 of this Annual Report for additional information).

All material restatement information that relates to the Misstatements is included in this Annual Report, and we do not intend to separately amend other documents that the Company has previously filed with the SEC. As a result, the financial statements of the Company included in any documents that the Company has previously filed with the SEC should no longer be relied upon.

Control Considerations

Although management did not conduct a formal assessment of internal control over financial reporting as of December 31, 2025, in accordance with Section 215.02 of the SEC Division of Corporation Finance’s Regulation S-K Corporation Finance Interpretations, as a result of the errors described above and the related restatement, the Company identified certain material weaknesses in its internal control over financial reporting. As a result of the material weaknesses in internal control over financial reporting, our disclosure controls and procedures were not effective at a reasonable assurance level as of June 30, 2024, September 30, 2024, December 31, 2024, June 30, 2025, September 30, 2025, and December 31, 2025. Management will be implementing changes to strengthen our internal controls and remediate the material weaknesses. See Item 9A, “Controls and Procedures” for additional information related to the material weaknesses in internal control over financial reporting and our related remediation activities.

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CAUTIONARY NOTE ON FORWARD-LOOKING STATEMENTS

This Annual Report contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and is intended to qualify for the safe harbor from liability established by the Private Securities Litigation Reform Act of 1995. All statements contained in this Annual Report other than statements of historical fact are forward-looking statements.

Forward-looking statements generally relate to future events or our future financial or operating performance. In some cases, you can identify forward-looking statements because they contain words such as “may,” “should,” “expect,” “intend,” “plan,” “anticipate,” “believe,” “estimate,” “predict,” “project,” “target,” “potential,” “continue,” “could,” “will,” “would,” or similar expressions, or the negative of these terms or similar expressions, although not all forward-looking statements contain these identifying words.

Forward-looking statements contained in this Annual Report include, but are not limited to, statements regarding our future results of operations and financial condition; business strategy; plans; objectives and expectations for our business; operations and technology; risks related to the restatement of our consolidated financial statements included in this Annual Report and for other periods impacted by the restatement as identified in our Current Report on Form 8-K filed with the SEC on April 9, 2026, and any potential litigation or investigation related to such restatement; our ability to maintain effective internal control over financial reporting and disclosure controls and procedures, including our ability to remediate any existing material weaknesses in our internal control over financial reporting and the timing of any such remediation, as well as to reestablish effective disclosure controls and procedures at a reasonable assurance level; and the assumptions underlying or relating to any of the foregoing. These forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to differ materially from those expressed or implied by the forward-looking statements.

Important factors that could cause actual results to differ materially from those in the forward-looking statements in this Annual Report include, among other things, the factors summarized below:

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The foregoing does not represent an exhaustive list of factors that could impact the forward-looking statements contained herein or the risk factors that we are faced with. Moreover, we operate in a highly regulated, capital-intensive and evolving industry, and new risks and uncertainties may emerge from time to time that could affect our business, prospects, results of operations, or financial condition.

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Forward-looking statements in this Annual Report are based on management’s current expectations, estimates, forecasts, projections, beliefs and assumptions and on information available to us as of the date of this Annual Report. Although we believe that the expectations reflected in these forward-looking statements are reasonable, we cannot assure you that such expectations will prove to be correct. Forward-looking statements are inherently subject to known and unknown risks, uncertainties and other factors, many of which are beyond our control, that could cause our actual results, performance, developments or achievements to differ materially from those expressed in or implied by the forward-looking statements.

Accordingly, you should not place undue reliance on forward-looking statements. Forward-looking statements speak only as of the date of this Annual Report. Except as required by applicable law, we undertake no obligation to update or revise any forward-looking statements to reflect events or circumstances after the date of this Annual Report or to reflect the occurrence of unanticipated events.

Implications of Being an Emerging Growth Company and a Smaller Reporting 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 (“JOBS Act”). An emerging growth company may take advantage of reduced reporting requirements that are otherwise applicable to public companies. These provisions include, but are not limited to:

We may use these provisions until the last day of our fiscal year in which the fifth anniversary of the first sale of our common stock pursuant to an effective registration statement occurs. However, if certain events occur prior to the end of such five-year period, including if we become a “large accelerated filer,” our annual gross revenues exceed $1.235 billion or we issue more than $1.00 billion of non-convertible debt in any three-year period, we will cease to be an emerging growth company prior to the end of such five-year period.

We have elected to take advantage of certain of the reduced disclosure obligations in this Annual Report 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 other public reporting companies.

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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, until those standards apply to private companies. We have elected to take advantage of the benefits of this extended transition period and, therefore, we will not be subject to the same new or revised accounting standards as other public companies that are not emerging growth companies, until these standards apply to private companies. Our financial statements may therefore not be comparable to those of companies that comply with such new or revised accounting standards. Until the date that we are no longer an emerging growth company or affirmatively and irrevocably opt out of the exemption provided by Section 7(a)(2)(B) of the Securities Act upon issuance of a new or revised accounting standard that applies to our financial statements and that has a different effective date for public and private companies, we will disclose the date on which we will adopt the recently issued accounting standard. We are also a “smaller reporting company,” as defined in the Exchange Act, meaning that the market value of our stock held by non-affiliates was less than $700 million and our annual revenue was less than $100 million during the most recently completed fiscal year. We will continue to be a smaller reporting company until the last day of the fiscal year in which either (i) the market value of our stock held by non-affiliates is more than $250 million measured on the last business day of our second fiscal quarter or (ii) our annual revenue is more than $100 million during the most recently completed fiscal year and the market value of our stock held by non-affiliates is more than $700 million measured on the last business day of our second fiscal quarter. 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 have chosen, and may in the future 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. Likewise, if we are an emerging growth company at the time we cease to be a smaller reporting company, we may continue to rely on exemptions from certain disclosure requirements that are available to emerging growth companies.

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 (the “Merger Closing Date”), 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 principal executive offices are located at 2001 Addison St., Suite 300, Berkeley, California 94704. Our telephone number is (707) 400-0778. Our website address is*www.deepfission.com.*The information contained on, or accessible through, our website is not incorporated by reference into this Annual Report, and the references to our website are intended to be inactive textual references only.

All trademarks, service marks and trade names appearing in this Annual Report are the property of their respective holders. Use or display by us of other parties’ trademarks, trade dress, or products in this Annual Report is not intended to, and does not, imply a relationship with, or endorsements or sponsorship of, us by the trademark or trade dress owners.

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