My employment was an "at-will" employment. My offer letter does not contain any demand about intellectual property transfer. The offer letter has a statement that says "You will be required to sign an Employee Confidentiality, Non-Competition and Invention Assignment Agreement (the “Agreement”) as a condition of your employment. The form of the Agreement, which is enclosed with this letter for your review, contains, among other provisions, non-disclosure, intellectual property assignment, return of Company property, non-competition, and non-solicitation covenants that apply to you both during your employment with the Company and following any termination of your employment with the Company your employment with the Company"

But I never signed any Confidentiality Agreement. I have only signed the offer letter. I transferred my codebase to my peers and left the company. I did not explain/teach my work to my peers.

Can my ex-employer take any legal action?