SEC Form 424B7 filed by CID HoldCo Inc.

Filed Pursuant to Rule 424(b)(7)

Registration No. 333-290052

Prospectus Supplement

(To Prospectus dated December 10, 2025)

CID HoldCo, Inc.

Up to 29,701,559 shares of Common Stock (for resale)

655,000 Warrants to Purchase shares of Common Stock (for resale)

Up to 14,999,983 shares of Common Stock Issuable upon Exercise of the Warrants (for issuance)

This prospectus supplement (“Prospectus Supplement”) updates and supplements the prospectus dated December 10, 2025 (as amended and supplemented, the “Prospectus”), which forms a part of our Post-Effective Amendment No. 1 to the Registration Statement on Form S-1 (Registration No. 333-290052) relating, in part, to the offer and sale from time to time of up to 29,701,559 shares of Common Stock (the “Total Resale Shares”). This Prospectus Supplement is being filed to supplement the information in the Prospectus related to the Selling Securityholders table and the selling securityholders identified therein (including their transferees, donees, pledgees and other successors-in-interest) (the “Selling Securityholders”) to reflect the assignment of certain shares of our common stock, par value $0.0001 per share (the “Common Stock”), by Fir Tree Credit Opportunity Master Fund, LP formerly known as Fir Tree Capital Opportunity Master Fund III, LP, which was identified as a Selling Securityholder in the Prospectus, to certain of its affiliates as herein identified. Capitalized terms used, but not otherwise defined herein, shall have the meanings ascribed thereto in the Prospectus.

We will not receive any proceeds from the sale of shares of our Common Stock or Warrants by the Selling Securityholders pursuant to the Prospectus, except with respect to amounts received by us upon exercise of the Public Warrants to the extent such Public Warrants are exercised for cash, which amount of aggregate proceeds, assuming the exercise of all Public Warrants for cash, could be up to approximately $172,499,805. We believe the likelihood that Public Warrant holders will exercise their Public Warrants, and therefore the amount of cash proceeds that we would receive, is dependent upon the market price of our Common Stock. If the market price for our Common Stock is less than $11.50 per share, we believe the Public Warrant holders will be less likely to exercise their Warrants. We will pay the expenses, other than underwriting discounts and commissions and expenses incurred by the Selling Securityholders for brokerage, accounting, tax or legal services or any other expenses incurred by the Selling Securityholders in disposing of the securities, associated with the sale of securities pursuant to this prospectus.

This Prospectus Supplement should be read in conjunction with and accompanied by the Prospectus and is qualified by reference to the Prospectus, except to the extent that the information in this Prospectus Supplement supersedes the information contained in the prospectus.

Our Common Stock and Public Warrants are traded on the Nasdaq Stock Market LLC under the symbol “DAIC” and “DAICW”, respectively. On December 29, 2025, the last reported sale price of our Common Stock on the Nasdaq Stock Market LLC was $0.3955 per share, and the closing price of our Public Warrants was $0.104 per Public Warrant.

We are an “emerging growth company” under federal securities laws and are subject to reduced public company reporting requirements.

Investing in our Common Stock involves a high degree of risk. See “Risk Factors” beginning on page 7 of the Prospectus.

Neither the Securities and Exchange Commission 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.

The date of this prospectus supplement is December 31, 2025

SELLING SECURITYHOLDERS

The Selling Securityholders listed in the table below may from time to time offer and sell any or all of the shares of Common Stock and Warrants set forth below pursuant to the Prospectus. When we refer to the “Selling Securityholders” in the Prospectus, we refer to the persons listed in the table below, and the pledgees, donees, permitted transferees, assignees, successors and others who later come to hold any of the Selling Securityholders’ interest in the shares of Common Stock after the date of this prospectus other than through a public sale.

The following table sets forth, as of the date of this prospectus:

Our registration of the shares of Common Stock does not necessarily mean that the Selling Securityholders will sell all or any of such Common Stock. A Selling Securityholder may sell all, some or none of such securities in this offering. See “Plan of Distribution” in the Prospectus.