Does fasting become invalidated if someone who intended to fast then slept before the Adhan?

For the fast to be valid, the intention must be decisive, meaning the intention to fast without hesitation. So, whoever intends to fast conditionally, such as intending to fast tomorrow if it is Ramadan, their fast is not valid due to the lack of decisiveness. The questioner's pre-dawn meal (suhoor) and waiting for the Fajr adhan are indications of their intention to fast, and their previous intention to break the fast if they slept does not harm them. Furthermore, verbalizing the intention is not a condition; rather, a mere resolve to fast in the heart is sufficient. The pre-dawn meal (suhoor) for the sake of fasting is proof that the intention has been formed.