Capital World Investors holds 5.72M ATI shares (NYSE: ATI)

Rhea-AI Filing Summary

ATI Inc. Schedule 13G/A discloses that Capital World Investors reports beneficial ownership of 5,719,812 shares of ATI common stock, representing 4.2% of 136,462,390 shares outstanding as of 03/31/2026. The filing states CWI has sole voting and dispositive power over these shares.

Insights

Institutional Ownership Analyst

Large institutional holder reports a 4.2% stake in ATI.

Capital World Investors is disclosed as beneficial owner of 5,719,812 shares with sole voting and dispositive power. The filing identifies the investor as a division of Capital Research and Management Company and its related investment management entities.

Holder size is notable for monitoring potential voting influence; subsequent filings may show changes. The filing does not state any planned transactions or cash‑flow treatment.

Key Figures

Shares beneficially owned: 5,719,812 shares Percent of class: 4.2% Shares outstanding (reported): 136,462,390 shares

3 metrics

Shares beneficially owned 5,719,812 shares Beneficial ownership reported by Capital World Investors

Percent of class 4.2% Percentage of <b>136,462,390</b> shares outstanding as of <date>03/31/2026</date>

Shares outstanding (reported) 136,462,390 shares Shares believed to be outstanding as stated in the filing

Key Terms

Schedule 13G/A, Beneficial owner, Sole dispositive power, Sole voting power

4 terms

Schedule 13G/A regulatory

"Item 1. (a) Name of issuer: ATI Inc.; form header shows Amendment No. 1"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

Beneficial owner financial

"Item 4. Ownership (a) Amount beneficially owned: 5,719,812"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

Sole dispositive power financial

"Item 4. (c)(iii) Sole power to dispose or to direct the disposition of: 5,719,812"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

Sole voting power financial

"Item 4. (c)(i) Sole power to vote or to direct the vote: 5,719,812"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

ATI Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

01741R102

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 01741R102

1

Names of Reporting Persons

Capital World Investors

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 5,719,812.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 5,719,812.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

5,719,812.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

4.2 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: ATI Inc.
(b)	Address of issuer's principal executive offices: 2021 MCKINNEY AVENUE, DALLAS, TX 75201
Item 2.
(a)	Name of person filing: Capital World Investors
(b)	Address or principal business office or, if none, residence: 333 SOUTH HOPE STREET, 55TH FLOOR, LOS ANGELES, CALIFORNIA 90071
(c)	Citizenship: N/A
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 01741R102
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 5,719,812 ** **Capital World Investors ("CWI") is a division of Capital Research and Management Company ("CRMC"), as well as its investment management subsidiaries and affiliates Capital Bank and Trust Company, Capital International, Inc., Capital International Limited, Capital International Sarl, Capital International K.K., Capital Group Private Client Services, Inc., and Capital Group Investment Management Private Limited (together with CRMC, the "investment management entities"). CWI's divisions of each of the investment management entities collectively provide investment management services under the name "Capital World Investors." CWI is deemed to be the beneficial owner of 5,719,812 shares or 4.2% of the 136,462,390 shares believed to be outstanding.
(b)	Percent of class: 4.2 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 5,719,812
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 5,719,812
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Capital World Investors

Signature:	Jae Won Chung
Name/Title:	Senior Vice President and Associate General Counsel, Capital Research and Management Company
Date:	05/13/2026

FAQ

What does the ATI (ATI) Schedule 13G/A filed by Capital World Investors show?

It shows Capital World Investors beneficially owns 5,719,812 shares of ATI, representing 4.2% of 136,462,390 shares outstanding as of 03/31/2026. The filing reports sole voting and dispositive power.

Does the Schedule 13G/A indicate Capital World Investors plans to sell or buy ATI shares?

No transaction plan is stated. The filing discloses beneficial ownership and voting/dispositive power only; it does not report any proposed purchases, sales, or changes in holdings.

Who is the reporting entity on the ATI Schedule 13G/A?

The reporting entity is Capital World Investors, a division of Capital Research and Management Company and affiliated investment management entities, as detailed in the filing's ownership disclosure.

What voting power does Capital World Investors have over ATI shares?

The filing reports sole voting power of 5,719,812 shares and sole dispositive power of 5,719,812 shares, with zero shared voting or dispositive power listed.

How significant is a 4.2% stake in ATI reported on this filing?

A 4.2% stake is a material institutional holding but below common 5% reporting thresholds for other forms; the filing classifies this as ownership of 5 percent or less of a class.