Equity awards vest for Amentum Holdings (AMTM) Chief Legal Officer

Rhea-AI Filing Summary

Amentum Holdings, Inc. Chief Legal Officer & GC Michele T. St. Mary reported equity award activity tied to restricted stock units on February 17, 2026. 7,080 restricted stock units vested and converted into the same number of common shares, and 2,308 common shares were withheld to cover taxes. Following these transactions, she directly owned 27,043 shares of common stock and 14,162 restricted stock units.

Insider Trade Summary

7,080 shares exercised/converted

Mixed 3 txns

Insider St. Mary Michele T

Role Chief Legal Officer & GC

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units	7,080	$0.00	--
Exercise	Common Stock	7,080	$0.00	--
Tax Withholding	Common Stock	2,308	$30.05	$69K

Holdings After Transaction: Restricted Stock Units — 14,162 shares (Direct); Common Stock — 29,351 shares (Direct)

Footnotes (1)

1. Represents distribution of AMTM common stock upon vesting of restricted stock units. Represents number of shares of AMTM common stock tendered for tax withholding upon vesting of restricted stock units. Each restricted stock unit represents a contingent right to receive one share of AMTM common stock. The restricted stock units awarded vested on February 17, 2026.

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

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

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

St. Mary Michele T

(Last) (First) (Middle)

C/O AMENTUM HOLDINGS, INC.

4800 WESTFIELDS BOULEVARD, SUITE 400

(Street)

CHANTILLY VA 20151

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Amentum Holdings, Inc. [ AMTM ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Legal Officer & GC

3. Date of Earliest Transaction (Month/Day/Year)
02/17/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	02/17/2026		M		7,080	A	(1)	29,351	D
Common Stock	02/17/2026		F		2,308(2)	D	$30.05	27,043	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Restricted Stock Units	(3)	02/17/2026		M(1)			7,080	(4)	(4)	Common Stock	7,080	$0	14,162	D

Explanation of Responses:

1. Represents distribution of AMTM common stock upon vesting of restricted stock units.

2. Represents number of shares of AMTM common stock tendered for tax withholding upon vesting of restricted stock units.

3. Each restricted stock unit represents a contingent right to receive one share of AMTM common stock.

4. The restricted stock units awarded vested on February 17, 2026.

Remarks:

	/s/ Indira Lall, Attorney-in-fact	02/18/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transactions did Amentum (AMTM) report for Michele T. St. Mary?

Michele T. St. Mary reported vesting of 7,080 restricted stock units that converted into 7,080 shares of Amentum common stock, plus withholding of 2,308 shares for taxes tied to that vesting event.

How many Amentum (AMTM) restricted stock units vested in this Form 4?

The filing shows 7,080 restricted stock units vested, each representing a contingent right to receive one share of Amentum common stock. These units vested and distributed as shares on February 17, 2026, according to the reported footnotes.

Were any Amentum (AMTM) shares sold on the open market in this Form 4?

The Form 4 reports a disposition of 2,308 Amentum shares coded as “F,” which represents shares tendered for tax withholding upon RSU vesting, rather than an open-market sale transaction by the insider.

What is Michele T. St. Mary’s Amentum (AMTM) share ownership after these transactions?

After the reported transactions, Michele T. St. Mary directly owned 27,043 shares of Amentum common stock and 14,162 restricted stock units, as disclosed in the post-transaction ownership fields in the Form 4 data.

What date did the Amentum (AMTM) restricted stock units vest for Michele T. St. Mary?

The footnotes state that the restricted stock units awarded to Michele T. St. Mary vested on February 17, 2026, triggering distribution of Amentum common stock and related tax-withholding share tendering.

How does the Form 4 describe the nature of Amentum (AMTM) tax-withholding shares?

The filing explains that 2,308 Amentum shares represent stock tendered for tax withholding upon vesting of restricted stock units, consistent with transaction code F for payment of tax liability using securities.