And if it is an asset acquisition then you're technically still employed by your old company and you'd need to formally apply for a job at the new one.
These kind of details are exactly why you should hire a labour lawyer. Also, your 100% that if it is a share purchase (even if only a majority stake) that the old contract is simply still valid.
Acquisitions of any kind don't magically invalidate all the contracts the company has entered in over its lifespan.
Like I say depending on the jurisdiction the existing terms may have to be respected due to operation of law.
That's the case in the EU with the Acquired Rights Directive (and national implementations) which covers transfers of businesses/undertakings. Employees will automatically transfer, provided that in certain cases employer can update terms and conditions/make redundancies where justified (so called ‘economic, technical or organisational reasons’).
These kind of details are exactly why you should hire a labour lawyer. Also, your 100% that if it is a share purchase (even if only a majority stake) that the old contract is simply still valid.
Acquisitions of any kind don't magically invalidate all the contracts the company has entered in over its lifespan.