Form 8-K

8-K — ADTRAN Holdings, Inc.

Accession: 0001193125-26-342359

Filed: 2026-08-10

Period: 2026-08-10

CIK: 0000926282

SIC: 3661 (TELEPHONE & TELEGRAPH APPARATUS)

Item: Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers

Item: Financial Statements and Exhibits

Documents

8-K — adtn-20260810.htm (Primary)

EX-10.1 (adtn-ex10_1.htm)

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8-K

8-K (Primary)

Filename: adtn-20260810.htm · Sequence: 1

8-K

0000926282false00009262822026-08-102026-08-10

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): August 10, 2026

ADTRAN Holdings, Inc.

(Exact name of Registrant as Specified in Its Charter)

Delaware

001-41446

87-2164282

(State or Other Jurisdiction

of Incorporation)

(Commission File Number)

(IRS Employer

Identification No.)

901 Explorer Boulevard

Huntsville, Alabama

35806-2807

(Address of Principal Executive Offices)

(Zip Code)

Registrant’s Telephone Number, Including Area Code: (256) 963-8000

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading

Symbol(s)

Name of each exchange on which registered

Common Stock, Par Value $0.01 per share

ADTN

Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On August 10, 2026, Adtran Networks SE (“Adtran Networks”), a majority-owned subsidiary of ADTRAN Holdings, Inc. (the “Company”), entered into an amendment (the “Amendment”) to its employment agreement with Christoph Glingener, the Company’s Chief Technology Officer (“CTO”) and the CTO and a member of the management board of Adtran Networks. The Amendment provides that the term of Dr. Glingener’s employment agreement remains in force through December 31, 2026 and affirms that Dr. Glingener’s annual base salary remains €400,000.

The Amendment further provides that Dr. Glingener will continue to be eligible to receive an annual grant of an incentive cash bonus award tied to the Company’s total revenue and adjusted earnings before interest and taxes, with the targeted size of the grant to equal 60% of Dr. Glingener’s base salary. Additionally, Dr. Glingener remains eligible to receive annual grants of time-based restricted stock units (“RSUs”), with the target size of the annual RSU grant to equal 75% of Dr. Glingener’s base salary. The RSUs are subject to a cap of €903,729.

Additionally, the Amendment provides that Dr. Glingener shall receive an award of three-year financial plan performance stock units (the “long-term financial plan PSU awards”) with a target grant size amount of €903,729, which grant shall be divided into three separate annual tranches. The performance objective of the long-term financial plan PSU awards is based upon the Company’s Adjusted EBIT over the performance period of January 1, 2026 through December 31, 2028, subject to adjustment based on the Company’s relative total shareholder return over such performance period. Dr. Glingener’s long-term financial plan PSU awards are subject to a cap of €2,000,000. As previously disclosed, the Compensation Committee of the Board of Directors of the Company (the “Compensation Committee”) does not intend to grant annual PSU awards tied to the performance objective of the Company’s relative total shareholder return (referred to as market-based PSUs in the Company’s definitive proxy statement filed with the SEC on March 27, 2026) to any of the named executive officers going forward.

Consistent with the terms of the Amendment, grants of time-based RSUs and long-term financial plan PSUs were issued to Dr. Glingener on August 10, as approved by the Compensation Committee.

Finally, the Amendment provides that Dr. Glingener’s total annual remuneration remains capped at €2,800,000.

The foregoing descriptions of the Amendment, the time-based RSUs and the long-term financial plan PSU awards are not complete and are qualified in their entirety by the Amendment, the form of Restricted Stock Unit Agreement and the form of 2026 3-Year Performance Shares Agreement, respectively, which are attached hereto as Exhibits 10.1, 10.2 and 10.3 and are incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits.

Exhibit Number

Description

10.1

Twenty-First Amendment to Employment Agreement, dated August 10, 2026, by and between Adtran Networks SE and Christoph Glingener

10.2

Form of 2026 Restricted Stock Unit Agreement under the ADTRAN Holdings, Inc. 2024 Employee Stock Incentive Plan (incorporated by reference to Exhibit 10.4 to the Company’s Form 10-Q filed May 5, 2026)

10.3

Form of 2026 3-Year Performance Shares Agreement under the ADTRAN Holdings, Inc. 2024 Employee Stock Incentive Plan (incorporated by reference to Exhibit 10.2 to the Company’s Form 8-K filed April 7, 2026)

104

Cover Page Interactive Data File – the cover page iXBRL tags are embedded within the Inline XBRL document

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

ADTRAN Holdings, Inc.

Date:

August 10, 2026

By:

/s/ Timothy Santo

Timothy Santo

Senior Vice President of Finance and Chief

Financial Officer

EX-10.1

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EX-10.1

Amendment to Officer's Employment AgreemeRt- Dienstvertragsanderung fur Vorstandsmitglied

Exhibit 10.1

AMENDMENT TO OFFICER'S EMPLOYMENT AGREEMENT

DIENSTVERTRAGSANDERUNG VORSTANDSMITGLIED

Adtran Networks SE, Martinsried/Meiningen

- hereinafter the "Company" -

represented by the Supervisory Board

- im Folgenden die "Gesellschaft" -

vertreten durch den Aufsichtsrat

•

And und

Mr./Herrn

Dr. Christoph Glingener

Sandweg 7 26349Jade

- hereinafter: the "Officer" -

Preamble

- im Folgenden: das "Vorstandsmitglied" -

Praambel

The Officer has been a member of the management-' board of the Company· since January 1, 2007. The current Officer's Employment Agreement remains in full force and effect and continues until December 31, 2026.

The current Officer's Employment Agreement was extended the last time on December 9, 2025, until December 31, 2026, and unless expressly modified hereinafter remains in full force and effect and continues until December 31, 2026.

On June 15, 2026, the Annual General Meeting of the Company approved a new remuneration system for the members of the Management Board of the Company ("Remuneration System'').

The parties enter into this Amendment for the purpose of aligning the Officer's remuneration with the Remuneration System only for the calendar year 2026.

Intentionally left blank

Amendment to Officer's Employment Agreement - Dienstvertragsanderung fur Vorstandsmitglied

Das Vorstandsmitglied ist seit 1. Januar 2007 Mitglied des Vorstands der Gesellschaft. Der bestehende Dienstvertrag mit dem Vorstandsmitglied ist befristet und endet mit Ablauf des 31. Dezember 2026.

Der bestehende Dienstvertrag mit dem Vorstandsmitglied wurde zuletzt am 9. Dezember 2025 bis zum 31. Dezember 2026 verlangert, und bleibt so weit nicht nachfolgend ausdrucklich geandert bis zum Ablauf des 31. Dezember 2026 unverandert in Kraft.

Die Hauptversammlung der Gesellschaft hat am 15. Juni 2026 ein neues Vergutungssystem fur die Mitglieder des Vorstands der Gesellschaft (,,Vergutungssystem'') gebilligt.

Die Parteien schlieBen diesen Nachtrag, um die Vergutung des Vorstandsmitglieds an das Vergutungssystem nur fur das Kalenderjahr 2026 anzupassen.

Absichtlich freibleibend

Adtran Confidential

•

Remuneration System .

The Officer's remuneration shall be governed by the Remuneration System, as specified in the attached Exhibit 1.

Miscellaneous

4.1

Nothing in the Employment Agreement, as amended, shall be construed to prohibit the Officer from having reported or reporting possible violations of federal law or regulation or having filed or filing a charge or complaint with any governmental agency or entity, including, but not limited to the Department of Justice, Equal Employment Opportunity Commission, National Labor Relations Board, the Occupational Safety and Health Administration, the Securities and Exchange Commission, Congress, the Inspector General or any federal, state or local governmental agency or commission (each, a "Government Agency"). This Employment Agreement does not limit the Officer's ability to communicate with any Government Agency or otherwise participate in any investigation or proceeding that may be conducted by any Government Agency, including providing documents or other information, without notice to the Company.

4.2

In addition to the Adtran Holdings, Inc. ("Adtran") Policy for the Recovery of Erroneously Awarded Compensation agreed on November 27, 2023 / December 4, 2023, the malus and clawback clauses provided in Section 5 of the Management Board remuneration system approved by

Amendment to Officer's Employment AgreemeRt- Dienstvertragsanderung fur Vorstandsmitglied

Vergutungssystem

Die Vergutung des Vorstandsmitglieds richtet sich nach dem Vergutungssystem, wie in der beigefugten Anlage 1 naher festgelegt.

Sonstiges

4.1

Keine Bestimmung des Dienstvertrages in seiner geanderten Fassung ist so auszulegen, dass sie es dem Vorstandsmitglied verbietet, mogliche VerstoBe gegen Bundesgesetze oder - vorschriften zu melden oder eine Anzeige oder Beschwerde bei einer Regierungsbehorde oder -stelle einzureichen, einschlieBlich, aber nicht beschrankt auf das Justizministerium, die Equal Employment Opportunity Commission, das National Labor Relations Board, die Occupational Safety and Health Administration, die Securities and Exchange Commission, den Kongress, den Generalinspektor oder eine Regierungsbehorde oder -kommission auf Bundes-, Landes- oder Kommunalebene Qeweils eine "Regierungsbehorde"). Dieser Dienstvertrag schrankt die Fahigkeit des Vorstandsmitglieds nicht ein, mit einer Regierungsbehorde zu kommunizieren oder anderweitig an einer Untersuchung oder einem Verfahren teilzunehmen, das von einer Regierungsbehorde durchgefuhrt wird, einschlieBlich der Bereitstellung von Dokumenten oder anderen lnformationen, ohne dass die Gesellschaft davon in Kenntnis gesetzt wird.

4.2

Neben der am 27. November 2023 / 4. Dezember 2023 vereinbarten Adtran Holdings, Inc. ("Adtran") Policy for the Recovery of Erroneously Awarded Compensation gelten auch die in Ziff. 5 des Vorstandsvergutungssystems, das von der Hauptversammlung am 15. Juni 2026 gebilligt warden ist ("Vergutungssystem"),

the Annual General Meeting on June 15, 2026 ("Remuneration System") also apply.

vorgesehenen Einbehaltungs-Ruckforderungsklauseln.

und

4.3

In the event of termination of the Officer's Employment Agreement, the principles set out in Section 8 of the Remuneration System must be observed with regard to severance payments.

4.4

All other provisions of the existing Employ-ment Agreement, including all subsequent amendments, shall apply without change.

4.5

Modifications of this Agreement require written form. This shall also apply to the amendment of this clause requiring written form.

•

4.6

The German version will be authoritative for the interpretation of this Amendment.

4.3

4.4

Im Obrigen findet der bestehende Dienstvertrag einschlieBlich aIler nachfolgenden Anderungen und Erganzungen unverandert Anwendung.

4.5

Anderungen dieses Vertrages bedurfen der Schriftform. Dies gilt auch fur die Abanderungen dieser Schriftformklausel.

4.6

Fur die Auslegung dieses Vertrages ist die deutsche Fassung maBgeblich.

Amendment to Officer's Employment Agreement - Dienstvertragsanderung fur Vorstandsmitglied

[Signature Page follows}

Adtran Confidential

Amendment to Officer's Employment AgreemeRt- Dienstvertragsanderung fur Vorstandsmitglied

Munchen, 10.8.2026 2026 Munchen, 5.8.26 2026

/s/ Dr. Eduard Scheiterer /s/ Dr. Christoph Glingener

Dr. Eduard Scheiterer Dr. Christoph Glingener

Chairman of the Supervisory Board

. .

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