Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 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 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * Foster James Robert 2. Issuer Name and Ticker or Trading Symbol ATI INC [ATI] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) SVP, Finance and CFO (Last) (First) (Middle) C/O ATI INC., 2021 MCKINNEY AVENUE 3. Date of Earliest Transaction (Month/Day/Year) 01/05/2026 (Street) DALLAS, TX 75201 4. If Amendment, Date 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 (City) (State) (Zip) 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, par value $0.10 per share 01/05/2026 A 3,127(1) A $ 0 (2) 32,749 D Common Stock, par value $0.10 per share 01/05/2026 M 42,265 A $ 0 (3) 75,014 D Common Stock, par value $0.10 per share 01/05/2026 F 18,453(4) D $121.08(5) 56,561 D Common Stock, par value $0.10 per share 01/05/2026 A 6,517(6) A $ 0 (2) 63,078 D Common Stock, par value $0.10 per share 01/05/2026 F 2,835(7) D $121.08(5) 60,243 D Common Stock, par value $0.10 per share 01/05/2026 F 2,256(8) D $121.08(5) 57,987 D

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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 Underlying Securities (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 of Derivative Security: 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

Performance Stock Unit

$ 0 (3)

01/05/2026

M

25,641

12/31/2026(3)

12/31/2026(3)

Common Stock, par value $0.10 per share

70,442

$ 0 (3)

25,641

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Foster James Robert C/O ATI INC. 2021 MCKINNEY AVENUE DALLAS, TX 75201			SVP, Finance and CFO

Signatures

/s/ Amanda J. Skov, Attorney-in-Fact for James Robert Foster		01/23/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	Award of restricted stock units, which are settled in shares of stock upon vesting. The award vests in three equal annual installments on each of the first three anniversaries of the grant date.
(2)	Awarded under the Issuer's 2022 Incentive Plan.
(3)	Settlement of one-half of certain Performance Stock Units awarded in 2022 ("2022 Breakout Performance Units"), each of which represented a contingent right to receive shares of the Issuer's Common Stock if the Issuer's Common Stock achieved specified target market prices (based on a 20-trading day average) on the New York Stock Exchange ("NYSE") for at least 20 consecutive trading days (the "20-day Average Market Price") prior to December 31, 2025, up to a maximum of three shares per Unit. The shares underlying one-half of the 2022 Breakout Performance Units became payable as of January 5, 2026 following certification of the Issuer's achievement of the relevant performance criteria by the Compensation and Leadership Development Committee of the Company's Board of Directors (the "CLDC"). The remaining half of the 2022 Breakout Performance Units are scheduled by their terms to become payable in early 2027.
(4)	Shares withheld for the payment of taxes in connection with the settlement of 2022 Breakout Performance Units.
(5)	Represents the average of the high and low trading prices for one share of the Issuer's Common Stock on the NYSE on January 5, 2026.
(6)	Settlement of performance-vested restricted stock units that were granted in 2023, the vesting of which was contingent on the Issuer's total shareholder return relative to a specified peer group during the period from January 1, 2023 through December 31, 2025 (the "2023-2025 PSUs"). The shares underlying the 2023-2025 PSUs became payable as of January 5, 2026 following certification of the Issuer's achievement of the relevant performance criteria by the CLDC.
(7)	Shares withheld for the payment of taxes in connection with the settlement of the 2023-2025 PSUs.
(8)	Shares withheld for payment of taxes on restricted stock units awarded in 2023, 2024 and 2025. One third of each such award vested by the terms thereof on January 5, 2026.

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