Form 424B3 Arxis, Inc.

Filed Pursuant to Rule 424(b)(3)
Registration No. 333-299412

PROSPECTUS SUPPLEMENT NO. 2

(To Prospectus dated October 22, 2026)

13,351,964 Shares

Class A Common Stock

This Prospectus Supplement No. 2 supplements the prospectus dated October 22, 2026 (as supplemented to date, the “Prospectus”), which forms a part of our Registration Statement on Form S-1 (Registration Statement No. 333-299412). The Prospectus and this prospectus supplement relate to the disposition from time to time of up to 13,351,964 shares of Arxis Class A common stock, par value $0.01 (“Class A common stock”), which are held or may be held by the selling stockholders named in the Prospectus (the “Holders”). We are not selling any common stock under this prospectus and will not receive any of the proceeds from the sale of shares by the Holders.

This prospectus supplement should be read in conjunction with the Prospectus, which is to be delivered with this prospectus supplement. This prospectus supplement updates, amends and supplements the information included or incorporated by reference in the Prospectus. If there is any inconsistency between the information in the Prospectus and this prospectus supplement, you should rely on the information in this prospectus supplement.

This prospectus supplement is not complete without, and may not be delivered or utilized except in connection with, the Prospectus, including any amendments or supplements to it.

Current Report on Form 8-K

On October 29, 2026, we filed a Current Report on Form 8-K with the Securities and Exchange Commission. The text of such Form 8-K is attached hereto.

Investing in our Class A common stock involves a high degree of risk. See “Risk Factors” beginning on page 13 of the Prospectus.

Neither the Securities and Exchange Commission (“SEC”) nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Prospectus supplement dated October 29, 2026

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

FORM 8-K/A

(Amendment No. 1)

CURRENT REPORT

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

ARXIS, INC.

(Exact name of Registrant as Specified in Its Charter)

(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:

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

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. ☐

Explanatory Note

On August 18, 2026, Arxis, Inc. (the “Company”) filed a Current Report on Form 8-K (the "Initial 8-K") with the Securities and Exchange Commission (the "SEC") disclosing that on August 17, 2026, the Company closed on the transactions contemplated by the Agreement and Plan of Merger (the “Merger”) with Orion Merger Sub, Inc., a Minnesota corporation and a wholly owned subsidiary of Arxis (the “Merger Sub”), Omnetics Connector Corporation, a Minnesota corporation (“Omnetics”), and Gary Jacobs, President of Omnetics, in his capacity as shareholder representative (the “Shareholder Representative”), entered into on May 29, 2026 (the "Merger Agreement"). The aggregate consideration for the Merger was based on an agreed enterprise value, which was $770.0 million, subject to customary closing adjustments. At closing, the Company issued 13,351,964 shares of the Company’s Class A common stock, par value $0.01 per share (“Class A common stock”), to the former shareholders of Omnetics and funded $8.0 million of cash escrow accounts pursuant to the Merger Agreement. The issuance of the Company’s Class A common stock was made pursuant to an exemption from registration under Section 4(a)(2) of the Securities Act of 1933.

This Amendment No. 1 (this “Amendment”) amends the Initial 8-K to file the financial statements and pro forma financial information required by Items 9.01(a) and (b) of Form 8-K to be filed by amendment no later than 71 calendar days after the date on which the Initial 8-K was required to be filed. This Amendment should be read in conjunction with the Initial 8-K and the Company’s other filings with the SEC. Except as stated herein, this Amendment does not reflect events occurring after the filing of the Initial 8-K with the SEC on August 18, 2026 and no attempt has been made in this Amendment to modify or update other information as disclosed in the Initial 8-K.

Item 9.01 Financial Statements and Exhibits.

(a) Financial statements of business acquired.

(b) Pro forma financial information.

The unaudited pro forma combined statements of income of the Company for the nine months ended September 30, 2026 and for the year ended December 31, 2025, giving pro forma effect to the Company's acquisition of all outstanding equity securities of Omnetics, and the notes related thereto are filed as Exhibit 99.4 hereto and are incorporated herein by reference.

(d) Exhibits.

__________________________

* Previously filed.

** Filed herewith.

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.