I’d suggest spending the time to read the common opensource licenses and their CLAs if you haven’t already picked one, and think about what happens after the initial code is published, maybe prepare some internal documentation guides for how you’re expected to continue working on it after that.
Do you happen to have legal council at your company who deal with this? Does your company have prior experience doing this sort of thing.
In general, at large companies that have plenty of lawyers taking care of patents and copyrights and intellectual property, there is usually a clause put in the employment contract when employees are hired that stipulates that the company owns everything you develop 24/7, using whatever resources. Whether or not this is enforceable in practice in all jurisdictions and to what extent remains to be seen, what it does in practice is ensure that the company has “first dibs” on anything you develop, because any sane individual would like to avoid litigation in this case.
In these cases, there’s two ways to opensource code as an individual, one is for the company to do intellectual property reassignment into the employee. This means that the company hands over the ownership of the project to the individual code, patents and the lot, and from there on it has nothing to do with it. You’re free to attach a license and publish, what happens with the project afterwards is up to you.
This also usually serves to insulate the company by helping to limit their liability somewhat for employees hobby projects.
The other way is to assign a copyright license to the code and publish it. In which case company still owns all the IP, or it owns parts and has been previously licensed to publish the remainder.
In either case there needs to be a document trail leading up to someone who has power of attorney to act on behalf of the company in these matters.
If there’s not, an argument can be made that the employee is acting as an agent of the company at the time, but opposite argument can be made too, making the employee liable (to repeat, any sane person would avoid dealing with lawyers as much as possible).
After publishing the code - what do you do with third party contributions, and how do you handle continued development. You can move all development in the open, or you can periodically republish from internal repos. Typically, when you get pull requests from third parties, you’d ask the committers to sign CLAs, contributor license agreements, where they assign the copyright containing the lines of code to the company and provide patent licenses to any user of the code (common with Apache), or they license anyone to transitively use it under license conditions patents be damned (common with GPL), or they reassign the IP to the company (random CLAs out there).
If you have any unclean development practices of copy pasting code from different projects under various licenses (e.g. from stack overflow); that would now be done in the open, and the company would assume the responsibility for it.
Read the licenses, think about the future.