Exhibit 3.1

CERTIFICATE OF FOURTH AMENDMENT TO THE

AMENDED AND RESTATED

CERTIFICATE OF INCORPORATION

OF

GIGCAPITAL5, INC.

GigCapital5, Inc., a corporation organized and existing under the by virtue of the General Corporation Law of the State of Delaware (the “DGCL”), does hereby certify:

1. The name of the corporation is GigCapital5, Inc. The corporation was originally incorporated pursuant to the DGCL on January 19, 2021, under the name of GigCapital5, Inc.

2. The date of filing of the corporation’s original Certificate of Incorporation with the Secretary of State of the State of Delaware was January 19, 2021, and the date of filing the corporation’s Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware was September 23, 2021. Certificates of Amendment to the Amended and Restated Certificate of Incorporation were filed with the Secretary of State of the State of Delaware on each of September 23, 2022, March 28, 2023, and September 28, 2023.

3. The Board of Directors of the corporation has duly adopted resolutions setting forth proposed amendments to the Certificate of Incorporation of the corporation (as amended and restated prior to the date hereof), declaring said amendment to be advisable and in the best interests of the corporation and its stockholders and authorizing the appropriate officers of the corporation to solicit the consent of the stockholders therefor, which resolutions setting forth the proposed amendment are substantially as follows:

RESOLVED, that Section 9.1(b) of Article IX of the Amended and Restated Certificate of Incorporation of the corporation is amended and restated to read in its entirety as follows:

“Immediately after the Offering, a certain amount of the net offering proceeds received by the Corporation in the Offering (including the proceeds of any exercise of the underwriters’ over-allotment option) and certain other amounts specified in the Corporation’s registration statement on Form S-1, as initially filed with the Securities and Exchange Commission on March 9, 2021, as amended (the “Registration Statement”), shall be deposited in a trust account (the “Trust Account”), established for the benefit of the Public Stockholders (as defined below) pursuant to a trust agreement described in the Registration Statement. Except for the payment of deferred underwriting commissions and the withdrawal of interest to pay taxes, none of the funds held in the Trust Account (including the interest earned on the funds held in the Trust Account) will be released from the Trust Account until the earliest to occur of (i) the completion of the initial Business Combination, (ii) the redemption of 100% of the Offering Shares (as defined below) if the Corporation is unable to complete its initial Business Combination before March 31, 2024, and (iii) the redemption of shares in connection with a vote seeking to amend any provisions of the Amended and Restated Certificate relating to the Corporation’s pre-initial Business Combination activity and related stockholders’ rights (as described in Section 9.7). Holders of shares of Common Stock included as part of the units sold in the Offering (the “Offering Shares”) (whether such Offering Shares were purchased in the Offering or in the secondary market following the Offering and whether or not such holders are Founders (as such term is defined in the Registration Statement), officers or directors of the Corporation, or affiliates of any of the foregoing) are referred to herein as “Public Stockholders. The gross proceeds from the issuance of such promissory notes pursuant to subpart (ii) above of this Section 9.1(b) will be added to the proceeds from the Offering to be held in the Trust Account and shall be used in accordance with this Article IX to fund the redemption of the Offering Shares that have not been previously redeemed.”

4. That thereafter, said amendment was duly adopted in accordance with the provisions of Section 242 of the DGCL by written consent of stockholders holding the requisite number of shares required by statute given in accordance with and pursuant to Section 228 of the DGCL.

IN WITNESS WHEREOF, the corporation has caused this Certificate of Amendment to be signed this day of December 28, 2023.

Exhibit 10.1

FIFTH AMENDMENT

TO THE

INVESTMENT MANAGEMENT TRUST AGREEMENT

This Amendment No. 5 (this “Amendment”), dated as of December 28, 2023, to the Investment Management Trust Agreement (as defined below) is made by and between GigCapital5, Inc., a Delaware corporation (the “Company”), having its principal office located at 1731 Embarcadero Rd., Suite 200, Palo Alto, CA 94303, and Continental Stock Transfer & Trust Company, as trustee (“Trustee”). All terms used but not defined herein shall have the meanings assigned to them in the Trust Agreement.

WHEREAS, the Company and the Trustee entered into an Investment Management Trust Agreement dated as of September 23, 2021, as amended by that certain Amendment No. 1, dated September 23, 2022, Amendment No. 2, dated March 28, 2023, Amendment No. 3, dated September 28, 2023, and Amendment No. 4, dated December 7, 2023 (collectively, the “Trust Agreement”);

WHEREAS, Section 1(i) of the Trust Agreement sets forth the terms that govern the liquidation of the Trust Account under the circumstances described therein;

WHEREAS, at a special meeting of the Company held on December 28, 2023, the Company’s stockholders approved (i) a proposal to amend the Company’s amended and restated certificate of incorporation (the “A&R COI”) extending the date by which the Company has to consummate a business combination one (1) time, from December 31, 2023 to the date for completion of an initial business combination set forth in the Company’s Amended and Restated Certificate of Incorporation, as filed with the Secretary of State of the State of Delaware (as amended, the “Amended and Restated Certificate”), without depositing any additional amounts in the Trust Account; and

NOW THEREFORE, IT IS AGREED:

1. Section 1(i) of the Trust Agreement is hereby amended and restated in its entirety as follows:

“(i) Commence liquidation of the Trust Account only after and promptly after (x) receipt of, and only in accordance with, the terms of a letter from the Company (“Termination Letter”) in a form substantially similar to that attached hereto as either Exhibit A or Exhibit B signed on behalf of the Company by the Chief Executive Officer or Chief Financial Officer of the Company or by the Executive Chairman of the Board of Directors of the Company (the “Board”) or other authorized officer of the Company, and, in the case of a Termination Letter in a form substantially similar to the attached hereto as Exhibit A, acknowledged and agreed to by the Representatives, and complete the liquidation of the Trust Account and distribute the Property in the Trust Account, including interest (less up to $100,000 of interest that may be released to the Company to pay dissolution expenses in the case of a Termination Letter in the form of Exhibit B hereto and which interest shall be net of any taxes payable), only as directed in the Termination Letter and the other documents referred to therein, or (y) the date which is the later of (i) the final date for completion of an initial business combination set forth in the Company’s Amended and Restated Certificate of Incorporation, as filed with the Secretary of State of the State of Delaware (as amended, the “Amended and Restated Certificate”); and (ii) such later date as may be approved by the Company’s stockholders in accordance with the Company’s Amended and Restated Certificate if a Termination Letter has not been received by the Trustee prior to such date, in which case the Trust Account shall be liquidated in accordance with the procedures set forth in the form of letter attached hereto as Exhibit B and the Property in the Trust Account, including interest (less up to $100,000 of interest that may be released to the Company to pay dissolution expenses in the case of a Termination Letter in the form of Exhibit B hereto and which interest shall be net of any taxes payable), shall be distributed to the Public Stockholders of record as of such date; provided, however, that in the event the Trustee receives a Termination Letter in a form substantially similar to Exhibit B hereto, or if the Trustee begins to liquidate the Property because it has received no such Termination Letter by the date specified in clause (y) of this Section 1(i), the Trustee shall keep the Trust Account open until twelve (12) months following the date the Property has been distributed to the Public Stockholders;”

4. All other provisions of the Trust Agreement shall remain unaffected by the terms hereof.

5. This Amendment may be signed in any number of counterparts, each of which shall be an original and all of which shall be deemed to be one and the same instrument, with the same effect as if the signatures thereto and hereto were upon the same instrument. A facsimile signature or electronic signature shall be deemed to be an original signature for purposes of this Amendment.

6. This Amendment is intended to be in full compliance with the requirements for an Amendment to the Trust Agreement as required by Section 6(c) of the Trust Agreement, and every defect in fulfilling such requirements for an effective amendment to the Trust Agreement is hereby ratified, intentionally waived and relinquished by all parties hereto.

7. This Amendment shall be governed by and construed and enforced in accordance with the laws of the State of New York, without giving effect to conflicts of law principles that would result in the application of the substantive laws of another jurisdiction.

[signature page follows]

IN WITNESS WHEREOF, the parties have duly executed this Amendment to the Investment Management Trust Agreement as of the date first written above.

Exhibit 99.1

GigCapital5, Inc. Announces Stockholder Approval of Extension Amendment to the Amended and Restated

Certificate of Incorporation and Investment Management Trust Agreement

Palo Alto, CA – December 29, 2023 – GigCapital5, Inc. (“GigCapital5” or the “Company”) (NASDAQ: GIA), a blank check company, also commonly referred to as a special purpose acquisition company, or SPAC, formed for the purpose of entering into a merger, capital stock exchange, asset acquisition, stock purchase reorganization or similar business combination with one or more businesses or entities, today announced that on December 28, 2023, its stockholders approved an extension of the date by which it has to consummate a business combination, allowing the Company to extend such date one (1) time from December 28, 2023 until March 31, 2024 (the extension, the “Extension”).

About GigCapital5

GigCapital5 is a blank check company, also commonly referred to as a special purpose acquisition company, or SPAC, formed for the purpose of entering into a merger, capital stock exchange, asset acquisition, stock purchase reorganization or similar business combination with one or more businesses or entities. While GigCapital5’s efforts to identify a target business may span many industries, the focus of GigCapital5’s search is for prospects within the technology, media and telecommunications, aerospace and defense, advanced medical equipment, intelligent automation and sustainable industries. GigCapital5 was sponsored by GigAcquisitions5, LLC, which was founded by GigFounders, LLC, each a member entity of GigCapital Global, and formed for the purpose of entering into a merger, share exchange, asset acquisition, stock purchase, recapitalization, reorganization, or similar business combination with one or more businesses.

On December 8, 2022, GigCapital5 entered into a Business Combination Agreement (as amended, the “Business Combination Agreement” or “BCA”) with QTI Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of GigCapital5 (“Merger Sub”), and QT Imaging (the transactions contemplated by the Business Combination Agreement, the “Business Combination”). Pursuant to the terms of the Business Combination Agreement, Merger Sub will merge with and into QT Imaging (the “Merger”), with QT Imaging as the surviving company in the Merger (the “Surviving Corporation”), and after giving effect to the Merger, the Surviving Corporation will be a wholly owned subsidiary of GigCapital5, which will be renamed as QT Imaging Holdings, Inc. (“QTI Holdings”).

Additional Information and Where to Find It

In connection with the proposed Business Combination, GigCapital5 filed with the Securities and Exchange Commission (the “SEC”) a registration statement on Form S-4 (together with all amendment to such registration statement, the “Registration Statement”), which includes a preliminary proxy statement/prospectus (the “BCA Proxy Statement”) to be distributed to holders of GigCapital5 Common Stock in connection with GigCapital5’s solicitation of proxies for the vote by GigCapital5’s stockholders with respect to the Business Combination and the other matters as described in the Registration Statement and a prospectus relating to the offer of the securities to be issued to the stockholders of QT Imaging in connection with the Business Combination. After the Registration Statement has been filed and declared effective, GigCapital will mail a definitive BCA Proxy Statement, when available, to its stockholders. Investors and security holders and other interested parties are urged to read the BCA Proxy Statement, any amendments thereto and any other documents filed with the SEC carefully and in their entirety when they become available because they will contain important information about GigCapital5, QT Imaging and the proposed Business Combination. Such persons can also read GigCapital5’s Annual Report on Form 10-K and Current Reports on Form 8-K for more information on the security holdings of its officers and directors and their respective interests as security holders in the consummation of the Transactions described in this Current Report. The BCA Proxy Statement, Registration Statement, the Extension Proxy Statement, and GigCapital5’s other reports can be obtained, without charge, at the SEC’s web site (www.sec.gov) and on GigCapital5’s website at www.gigcapital5.com.

Participants in the Solicitation

GigCapital5, QT Imaging, and their respective directors, executive officers and other members of their management and employees, under SEC rules, may be deemed to be participants in the solicitation of proxies of GigCapital5 stockholders in connection with the extension of the business combination period until March 31, 2023 and approval of the proposed Business Combination. Investors and security holders may obtain more detailed information regarding the names, affiliations and interests of GigCapital5’s directors and officers in its Annual Report on Form 10-K for the fiscal year ended December 31, 2022, which was filed with the SEC on June 15, 2023. Information regarding the persons who may, under SEC rules, be deemed participants in the solicitation of proxies to GigCapital5’s stockholders in connection with the extension of the business combination period is set forth in the Extension Proxy Statement and approval of the proposed Business Combination is set forth in the BCA Proxy Statement for the proposed Business Combination. Information concerning the interests of GigCapital5’s and QT Imaging’s equity holders and participants in the solicitation, which may, in some cases, be different than those of GigCapital5’s and QT Imaging’s equity holders generally, is set forth in the Extension Proxy Statement relating to the extension of the business combination period. GigCapital5 stockholders, potential investors and other interested persons should read the Extension Proxy Statement and the BCA Proxy Statement carefully before making any voting or investment decisions.

Forward-Looking Statements:

This Current Report includes “forward-looking statements” within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995. The expectations, estimates, and projections of the businesses of GigCapital5 and QT Imaging may differ from their actual results and consequently, you should not rely on these forward-looking statements as predictions of future events. Words such as “expect,” “estimate,” “project,” “budget,” “forecast,” “anticipate,” “intend,” “plan,” “may,” “will,” “could,” “should,” “believes,” “predicts,” “potential,” “continue,” and similar expressions are intended to identify such forward-looking statements. These forward-looking statements include, without limitation, expectations of the management of QT Imaging with respect to the business and prospects of QT Imaging and the QTscan^® and other products of QT Imaging, the benefits of the proposed Business Combination, the plans, expectations and intentions of QT Imaging and GigCapital5, the satisfaction of the closing conditions to the proposed Business Combination, the timing of the completion of the proposed Business Combination and the future performance of QT Imaging, including the anticipated impact of the proposed Business Combination on this performance, the completion of the financing with Yorkville or the ability to raise any other financing in connection with the Business Combination, and the GigCapital5 ability to maintain its listing on any stock exchange following the September 2023 Meeting. These forward-looking statements involve significant risks and uncertainties that could cause the actual results to differ materially from the expected results. Most of these factors are outside of the control of GigCapital5 and QT Imaging and are difficult to predict. Factors that may cause such differences include, but are not limited to: (1) the ability of GigCapital5, QT Imaging and QTI Holdings to issue equity or equity-linked securities in connection with the proposed Business Combination or in the future, (2) the outcome of any legal proceedings that may be instituted against the parties following the announcement of the proposed Business Combination and the BCA; (3) the inability to complete the proposed Business Combination, including the risk that any regulatory approvals or the SEC’s declaration of the effectiveness of the BCA Proxy Statement are not obtained, are delayed or are subject to unanticipated conditions that could adversely affect QTI Holdings or the expected benefits of the proposed Business Combination or due to failure to obtain approval of the stockholders of GigCapital5 and QT Imaging or other conditions to closing; (4) the amount of redemption requests made by GigCapital5’s stockholders; (5) the impact of the COVID-19 pandemic on (x) the parties’ ability to consummate the proposed Business Combination and (y) the business of QT Imaging and QTI Holdings; (6) the receipt of an unsolicited offer from another party for an alternative business transaction that could interfere with the proposed Business Combination; (7) the inability to obtain or maintain the listing of GigCapital5 on the Nasdaq Stock Exchange or any other Exchange following the September 2023 Meeting or the listing of QTI Holdings’ common stock on the Nasdaq Stock Exchange or any other Exchange following the proposed Business Combination; (8) the risk that the proposed Business Combination disrupts current plans and operations as a result of the announcement and consummation of the proposed Business Combination; (9) the ability to recognize the anticipated benefits of the proposed Business Combination, which may be affected by, among other things, competition, the ability of QTI Holdings to grow and manage growth profitably and retain its key employees; (10) costs related to the proposed Business Combination; (11) changes in applicable laws or regulations; (12) the demand for QT Imaging’s and QTI Holdings’ services together with the possibility that QT Imaging or QTI Holdings may be adversely affected by other economic, business, and/or competitive factors; (13) risks and uncertainties related to QT Imaging’s business, including, but not limited to, the ability of QT Imaging to increase sales of its output products in accordance with its plan; (14) risks related to the rollout of QT Imaging’s business and the timing of expected business milestones; (15) the effects of competition on QT Imaging’s business; (16) changes

in domestic and foreign business, market, financial, political, and legal conditions; (17) the inability to close on the Yorkville SEPA or obtain any other financing to support the closing of the Business Combination and cover operating needs of QTI Holdings, and (18) other risks and uncertainties included in (x) the “Risk Factors” sections of the most recent Annual Report on Form 10-K and Quarterly Reports on Form 10-Q filed with the SEC by GigCapital5 and (y) other documents filed or to be filed with the SEC by GigCapital5. The foregoing list of factors is not exclusive. You should not place undue reliance upon any forward-looking statements, which speak only as of the date made. GigCapital5 and QT Imaging do not undertake or accept any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements to reflect any change in their expectations or any change in events, conditions, or circumstances on which any such statement is based.

No Offer or Solicitation

This Current Report will not constitute a solicitation of a proxy, consent or authorization with respect to any securities or in respect of the Business Combination. This Current Report will also not constitute an offer to sell or the solicitation of an offer to buy any securities, nor will there be any sale of securities in any states or jurisdictions in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities will be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act or an exemption therefrom.

GigCapital5, Inc. Contact:

Brian Ruby, ICR, [email protected]