cap-gap extension

I have a question regarding the cap-gap extension. Let's assume I am working at employer A and my H-1B petition filed by employer B is approved, making me eligible for the cap-gap extension. Since H-1B goes into effect from 1st October, can I continue to work at Employer A till 30th September using the cap-gap extension and start with Employer B from 1st October on H-1B? Is the cap-gap extension tied to an employer like H-1B or, is it similar to OPT and STEM-OPT, allowing a student to work for any valid employers till 09/30? #workvisa #h1b #opt #stemopt