Vistra files 8-K: entry into a material agreement, other material event

Item 1.01. Entry into a Material Definitive Agreement.

On September 24, 2026, Vistra Operations Company LLC (“Vistra Operations”), an indirect, wholly owned subsidiary of Vistra Corp. (“Vistra”), completed its underwritten public offering of $850,000,000 aggregate principal amount of its 7.000% Series A Junior Subordinated Notes due 2057 (the “Series A Notes”) and $650,000,000 aggregate principal amount of its 7.250% Series B Junior Subordinated

Notes due 2057 (the “Series B Notes” and, together with the Series A Notes, the “Notes”), in each case irrevocably and unconditionally guaranteed by Vistra (the “Guarantee” and, together with the Notes, the “Securities”). The Securities were issued pursuant to the Indenture, dated as of September 24, 2026 (the “Base Indenture”), among Vistra Operations, as issuer, Vistra, as guarantor, and Wilmington Trust, National Association, as trustee (the “Trustee”), as supplemented by the First

Supplemental Indenture, dated as of September 24, 2026 (together with the Base Indenture, the “Indenture”), among Vistra Operations, Vistra and the Trustee. The Indenture and the terms of the Securities are further described under “Description of the Notes” in the prospectus supplement of Vistra Operations and Vistra dated September 10, 2026, together with the related prospectus dated September 8, 2026, as filed with the Securities and Exchange Commission under Rule 424(b)(2) of the

Securities Act of 1933 on September 14, 2026, which descriptions are incorporated herein by reference. The sale of the Securities was registered under Vistra’s and Vistra Operations’ registration statement on Form S-3 filed on September 8, 2026 (File Nos. 333-298811 and 333-298811-01) (the “Registration Statement”).

Copies of the Base Indenture, the First Supplemental Indenture and the forms of the Notes of each series have been filed as Exhibits 4.1, 4.2, 4.3 and

4.4, respectively, to this report and are incorporated herein by reference and into the Registration Statement. The foregoing description of the Indenture and the Securities does not purport to be complete and is qualified in its entirety by reference to such exhibits.

Item 8.01. Other Events.

The Securities were sold pursuant to an Underwriting Agreement, dated September 10, 2026 (the “Underwriting Agreement”), among Vistra Operations, Vistra and Barclays Capital Inc., BofA Securities, Inc., Mizuho Securities USA LLC, MUFG Securities Americas Inc. and Truist Securities, Inc., as representatives of the several underwriters named in Schedule A to the Underwriting Agreement. A copy of the Underwriting Agreement has been filed as Exhibit 1.1 to this report and is incorporated herein by reference and into the Registration Statement. Additionally, the legal opinion of Sidley Austin LLP issued in connection with the offering of the Securities is attached hereto as Exhibit 5.1 and is incorporated herein by reference and into the Registration Statement.