Form of Restricted Stock Unit Award Agreement for grants under the Amentum Holdings, Inc. 2024 Stock Incentive Plan

Amentum Holdings, Inc. (the “Company”) has awarded to you (the “Participant”) the number of Restricted Stock Units specified and on the terms set forth below in consideration of your services (the “RSU Award”). Your RSU Award is subject to all of the terms and conditions as set forth herein and in the Company’s 2024 Stock Incentive Plan (the “Plan”) and the attached Award Agreement (the “Agreement”), which are incorporated herein in their entirety. Capitalized terms not explicitly defined herein but defined in the Plan or the Agreement shall have the meanings set forth in the Plan or the Agreement.

Participant:    [    ]

Date of Grant:    [    ]

Vesting Commencement Date:    [    ]

Number of Restricted Stock Units:    [    ]

The Restricted Stock Units subject to the RSU Award will vest in three substantially equal annual installments on the first three anniversaries of the Vesting Commencement Date, subject to the Participant’s employment or service with the Company or any Related Company through each applicable vesting date, or as otherwise provided in Schedule B attached to the Plan.

Issuance Schedule:    One share of Common Stock will be issued for each Restricted Stock Unit which vests, at the time set forth in Section 5 of the Agreement.

Participant Acknowledgements: By your signature below or by electronic acceptance or authentication in a form authorized by the Company, you understand and agree that:

•The RSU Award is governed by this RSU Award Grant Notice (the “Grant Notice”), and the provisions of the Plan and the Agreement, all of which are made a part of this document. Unless otherwise provided in the Plan, this Grant Notice and the Agreement (together, the “RSU Award Agreement”) may not be modified, amended or revised except in a writing signed by you and a duly authorized officer of the Company.

•You have read and are familiar with the provisions of the Plan, the RSU Award Agreement and the prospectus prepared for the Plan (the “Prospectus”). In the event of any conflict between the provisions in the RSU Award Agreement, or the Prospectus and the terms of the Plan, the terms of the Plan shall control.

•The RSU Award Agreement sets forth the entire understanding between you and the Company regarding the acquisition of Common Stock and supersedes all prior oral and written agreements, promises and/or representations on that subject with the exception of: (i) other equity awards previously granted to you, and (ii) any written employment agreement, offer letter, severance agreement, written severance plan or policy,

or other written agreement between the Company and you in each case that specifies the terms that should govern this RSU Award.

•Counterparts may be delivered via facsimile, electronic mail (including pdf or any electronic signature complying with the U.S. federal ESIGN Act of 2000, Uniform Electronic Transactions Act or other applicable law) or other transmission method, and any counterpart so delivered will be deemed to have been duly and validly delivered and be valid and effective for all purposes.

As reflected by your Restricted Stock Unit Grant Notice (“Grant Notice”), Amentum Holdings, Inc. (the “Company”) has granted you an RSU Award under its 2024 Stock Incentive Plan (the “Plan”) for the number of Restricted Stock Units as indicated in your Grant Notice (the “RSU Award”). The terms of your RSU Award as specified in this Award Agreement for your RSU Award (the “Agreement”) and the Grant Notice constitute your “RSU Award Agreement”. Defined terms not explicitly defined in this Agreement but defined in the Grant Notice or the Plan shall have the same definitions as in the Grant Notice or Plan, as applicable.

The general terms applicable to your RSU Award are as follows:

1.Governing Plan Document. Your RSU Award is subject to all the provisions of the Plan. Your RSU Award is further subject to all interpretations, amendments, rules and regulations, which may, from time to time, be promulgated and adopted pursuant to the Plan. In the event of any conflict between the RSU Award Agreement and the provisions of the Plan, the provisions of the Plan shall control.

2.Grant of the RSU Award. This RSU Award represents your right to be issued on a future date the number of shares of Common Stock that is equal to the number of Restricted Stock Units indicated in the Grant Notice, subject to your satisfaction of the vesting conditions set forth therein. Any additional Restricted Stock Units that become subject to the RSU Award pursuant to a Change in Capitalization as set forth in the Plan and the provisions of Section 3 below, if any, shall be subject, in a manner determined by the Board, to the same forfeiture restrictions, restrictions on transferability, and time and manner of delivery as applicable to the other Restricted Stock Units covered by your RSU Award.

3.Dividends. As described in Section 8(d) of the Plan, you shall be entitled to a Dividend Equivalent Right with respect to each Restricted Stock Unit subject to the RSU Award.

4.Withholding Obligations.

(a)Regardless of any action taken by the Company or, if different, the Related Company to which you provide service (the “Service Recipient”) with respect to any income tax, social insurance, payroll tax, fringe benefits tax, payment on account or other tax-related items associated with the grant, vesting, or settlement of the RSU Award or sale of the underlying Common Stock or other tax-related items related to your participation in the Plan and legally applicable to you (the “Tax Liability”), you hereby acknowledge and agree that the Tax Liability is your ultimate responsibility and may exceed the amount, if any, actually withheld by the Company or the Service Recipient. You further acknowledge that the Company and the Service Recipient (i) make no representations or undertakings regarding any Tax Liability in connection with any aspect of this RSU Award, including, but not limited to, the grant or vesting of the RSU Award, the issuance of Common Stock pursuant to such vesting, the subsequent sale of shares of Common Stock, and the payment of any dividends on the Common Stock; and (ii) do not commit to, and are under no obligation to, structure the terms of the grant or any aspect of the RSU Award to reduce or eliminate your Tax Liability or achieve a particular tax result. Further, if you are subject to Tax Liability in more than one jurisdiction, you acknowledge that the Company and/or the Service Recipient (or former service recipient, as applicable) may be required to withhold or account for Tax Liability in more than one jurisdiction.

issued or otherwise issuable to you in connection with the Award; provided, however, that to the extent necessary to qualify for an exemption from application of Section 16(b) of the Exchange Act, if applicable, such share withholding procedure will be subject to the express prior approval of the Board or the Company’s Compensation Committee; (iv) permitting or requiring you to enter into a “same day sale” commitment, if applicable, with a broker-dealer that is a member of the Financial Industry Regulatory Authority (a “FINRA Dealer”), pursuant to this authorization and without further consent, whereby you irrevocably elect to sell a portion of the shares of Common Stock to be delivered in connection with your Restricted Stock Units to satisfy the Tax Liability and whereby the FINRA Dealer irrevocably commits to forward the proceeds necessary to satisfy the Tax Liability directly to the Company or the Service Recipient; and/or (v) any other method determined by the Company to be in compliance with applicable law. Furthermore, you agree to pay the Company or the Service Recipient any amount the Company or the Service Recipient may be required to withhold, collect, or pay as a result of your participation in the Plan or that cannot be satisfied by the means previously described. In the event it is determined that the amount of the Tax Liability was greater than the amount withheld by the Company and/or the Service Recipient (as applicable), you agree to indemnify and hold the Company and/or the Service Recipient (as applicable) harmless from any failure by the Company or the applicable Service Recipient to withhold the proper amount.

5.Date of Issuance.

(a)The issuance of shares in respect of the Restricted Stock Units is intended to comply with, or be exempt from the application of, Section 409A of the Code and the RSU Award Agreement will be construed and administered consistent with that intent. Subject to the satisfaction of the Tax Liability withholding obligation, if any, in the event one or more Restricted Stock Units vests, the Company shall issue to you, on such date (or as soon as administratively practicable thereafter), one (1) share of Common Stock for each vested, but unsettled, Restricted Stock Unit. Each issuance date determined by this paragraph is referred to as an “Original Issuance Date.”

Units were no longer subject to a “substantial risk of forfeiture” within the meaning of U.S. Treasury Regulations Section 1.409A-1(d).

6.Transferability. Except as otherwise provided in the Plan, your RSU Award is not transferable, except by will or by the applicable laws of descent and distribution.

7.Change in Control. Your RSU Award is subject to the terms of any agreement governing a Change in Control involving the Company, including, without limitation, a provision for the appointment of a stockholder representative that is authorized to act on your behalf with respect to any escrow, indemnities and any contingent consideration.

8.No Liability for Taxes. As a condition to accepting the RSU Award, you hereby (a) agree to not make any claim against the Company, or any of its officers, directors, employees or Affiliates related to tax liabilities arising from the RSU Award or other Company compensation and (b) acknowledge that you were advised to consult with your own personal tax, financial and other legal advisors regarding the tax consequences of the RSU Award and have either done so or knowingly and voluntarily declined to do so.

9.Severability. If any part of this Agreement or the Plan is declared by any court or governmental authority to be unlawful or invalid, such unlawfulness or invalidity will not invalidate any portion of this Agreement or the Plan not declared to be unlawful or invalid. Any Section of this Agreement (or part of such a Section) so declared to be unlawful or invalid will, if possible, be construed in a manner which will give effect to the terms of such Section or part of a Section to the fullest extent possible while remaining lawful and valid.

10.Other Documents. You hereby acknowledge receipt of or the right to receive a document providing the information required by Rule 428(b)(1) promulgated under the Securities Act, which includes the Prospectus. In addition, you acknowledge receipt of the Company’s trading policy.

11.Questions. If you have questions regarding these or any other terms and conditions applicable to your RSU Award, including a summary of the applicable federal income tax consequences please see the Prospectus.