# EDGAR Filing Document

**Accession Number:** 0001918102
**File Stem:** 0001104659-25-120071
**Filing Date:** 2025-12
**Character Count:** 9692
**Document Hash:** d644dbfa6d1710bbb8c19045e1ff7d36
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-25-120071.hdr.sgml**: 20251211

**ACCESSION NUMBER**: 0001104659-25-120071

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 14

**CONFORMED PERIOD OF REPORT**: 20251209

**ITEM INFORMATION**: Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20251211

**DATE AS OF CHANGE**: 20251210

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** DEEP FISSION, INC.
- **CENTRAL INDEX KEY:** 0001918102
- **STANDARD INDUSTRIAL CLASSIFICATION:** ELECTRIC SERVICES [4911]
- **ORGANIZATION NAME:** 01 Energy & Transportation
- **EIN:** 874265302
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 000-56407
- **FILM NUMBER:** 251563160

**BUSINESS ADDRESS:**
- **STREET 1:** 2831 GARBER STREET
- **CITY:** BERKELEY
- **STATE:** CA
- **ZIP:** 94705
- **BUSINESS PHONE:** (707) 400-0778

**MAIL ADDRESS:**
- **STREET 1:** 2831 GARBER STREET
- **CITY:** BERKELEY
- **STATE:** CA
- **ZIP:** 94705

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Surfside Acquisition Inc.
- **DATE OF NAME CHANGE:** 20220317

?xml version='1.0' encoding='ASCII'?

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

**FORM 8-K**

**CURRENT REPORT**

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

**Date of Report (Date of earliest event reported): December 9, 2025**

**Deep Fission, Inc.**

(Exact name of registrant as specified in its charter)

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| | | |
|:---|:---|:---|
| **Delaware** | **000-56407** | **87-4265302** |
| (State or other jurisdiction<br> of incorporation) | (Commission File Number) | (IRS Employer<br> Identification No.) |

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| | |
|:---|:---|
| **2831 Garber Street**<br> **Berkeley, California** <br> (Address of principal executive offices) | **94705**<br> (Zip Code) |

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

N/A

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

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

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| |
|:---|
| Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) |
| Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) |
| Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) |
| Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) |

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

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

Emerging growth company ⌧

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

**Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.**

(e) On December 9, 2025, Deep Fission, Inc. entered into an offer letter with Elizabeth Muller, the Company's President and Chief Executive Officer and Chair of the Board. The agreement provides for an annual base salary of $475,000, an annual performance-based bonus opportunity with a target equal to 50% of base salary, and equity awards consisting of (i) an option to purchase 183,150 shares of the Company's common stock and (ii) 549,451 restricted stock units. Each equity award vests monthly over four years, with a one-year cliff. The offer letter also confirms Ms. Muller's eligibility under the Company's previously disclosed Executive Severance and Change in Control Policy. The terms of the offer letter were approved by the Company's Compensation Committee.

A copy of the offer letter is filed as Exhibit 10.1 to this Current Report.

**Item 9.01 Financial Statements and Exhibits**

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| | |
|:---|:---|
| **Exhibit No.** | **Description** |
| [**10.1**](tm2533117d1_ex10-1.htm) | [Offer Letter between Deep Fission, Inc. and Elizabeth Muller, dated December 9, 2025.](tm2533117d1_ex10-1.htm) |
| **104** | Cover Page Interactive Data File (Inline XBRL) |

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**SIGNATURE**

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

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| | |
|:---|:---|
|  | **DEEP FISSION, INC.** |
| Date: December 10, 2025 | /s/ Jon Gordon |
|  | Jon Gordon |
|  | General Counsel & Secretary |

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## Exhibit 10.1

**Exhibit 10.1**

![](tm2533117d1_ex10-1img001.jpg)

December 9, 2025

Elizabeth Muller

2831 Garber Street

Berkeley, CA94705

Dear Liz,

We are pleased to confirm your continuing employment as Deep Fission's President and Chief Executive Officer, as well as the Chair of our Board of Directors, on the following terms:

&nbsp;&nbsp;&nbsp;&nbsp;· **Base Salary**. Your annual base salary will be $475,000, paid in accordance with Deep Fission's
standard payroll practices, less required payroll deductions and withholdings, and subject to periodic review and adjustment by our Compensation
Committee.

&nbsp;&nbsp;&nbsp;&nbsp;· **Discretionary Performance Bonus**. You will be eligible for an annual performance-based bonus with
a target equal to 50% of your then-current base salary, based on performance goals established annually by our Compensation Committee.
Any bonus will be determined by the Committee in its discretion, based on Company and individual performance, and paid at the same time
bonuses are paid to other senior executives, provided that you must be employed by Deep Fission on the payment date to receive the bonus.

&nbsp;&nbsp;&nbsp;&nbsp;· **Equity Grant**. As approved by our Compensation Committee, you have been granted (a) an option to
purchase 183,150 shares of Deep Fission's common stock at an exercise price equal to the fair market value on the grant date and
(b) 549,451 restricted stock units. Both awards vest over four years with a one-year cliff and are subject to your continued employment
and to the terms of our Equity Incentive Plan, as amended, and applicable award agreements.

During your employment, you will be eligible to participate in Deep Fission's employee benefit plans on the same basis as other senior executives. Deep Fission maintains an unlimited paid-time-off policy under which time off does not accrue, carry over, or pay out upon separation. Statutory paid sick leave will be provided as required by applicable law. Deep Fission reserves the right to amend, suspend, or terminate its benefit plans from time to time.

You will also be eligible to participate in Deep Fission's Executive Severance and Change in Control Policy, which sets forth the terms and conditions under which severance payments, equity acceleration, and related benefits are provided. Any such payments or benefits will be subject to your execution of a separation agreement and release of claims, as well as the terms of that policy.

Your employment with Deep Fission is at will. This means that you may terminate your employment at any time and for any reason, and Deep Fission may terminate your employment with or without Cause at any time and for any reason, subject to any severance or change-in-control protections expressly provided in our Executive Severance and Change in Control Policy or any other written arrangement approved by the Board. The at-will nature of your employment may be modified only by a written agreement signed by you and an authorized officer of Deep Fission.

As a condition of your continued employment with Deep Fission, you must sign and comply with our Proprietary Information & Intellectual Property Agreement, pursuant to which all claims or disputes arising out of your employment will be subject to mandatory arbitration except as otherwise set forth in that agreement.

This offer letter, together with your Proprietary Information & Intellectual Property Agreement and our Equity Incentive Plan, Executive Severance and Change in Control Policy, and other applicable policies (each as amended from time to time), constitutes the entire agreement between you and Deep Fission and supersedes all prior agreements or understandings. Any accrued rights or obligations that remain outstanding as of the date of this offer letter (including vested equity awards and reimbursement rights) will survive in accordance with their terms. If any provision of this offer letter is held unenforceable, the remainder will remain in effect. This offer letter will be governed by the laws of the State of Delaware.

Thank you for your continued dedication to Deep Fission's mission to power humanity from a mile underground by delivering clean, reliable, and affordable energy. To accept this offer, please sign and date below and return this letter to my attention.

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| |
|:---|
| Sincerely, |
| **DEEP FISSION, INC.,** |
| /s/ Jonathon Angell |
| Jonathon Angell |
| Chair, Compensation Committee |
| Acknowledged and Agreed: |
| /s/ Elizabeth Muller |
| Elizabeth Muller |
| Date: December 9, 2025 |

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