Hi,

TAM might either :

a)Transport you internationally to GRU and consider the second flight an internal domestic flight; This way you are expected to do customs & immigration at GRU. I belive this is the most reasonable procedure. You get your luggage in Sao Paulo and recheck it at TAM counters where they also stamp your boarding pass for GRU access.

b)Consider both flghts internationals; The only way for them to consider the second flight international is that it might be the continuation of an arrival flight that ends in Rio, thus departs from the international sector. This way your luggage would be tagged all the way to Rio and would not be sent to customs in Sao Paulo. Customer is expected to clear customs in Rio.

Either way luggage should fly on the flight it has been tagged to, according to your ticket.

In option a) once you clear customs & immigration at GRU you are free to do whatever in Sao Paulo until departure later in the day.

If option b) and want to leave the airport you might, due to such a lengthier connection, clear immigration in Sao Paulo so you can leave the airport. Later in the evening you need to visit a TAM check-in counter for them to validate your boarding pass with a local GRU stamp that enables you to reenter the international area. Immigration officers would check your passport and boarding pass to Rio thus reasonably authorize you to fly to Rio without any more stamps on the passport.

Beware that if option b) you need TAM to stamp your boarding pass, otherwise you will not be able to enter the gates area. Technically they might want to assess a local GRU tax for originating pax but I believe you might convince them that it is not reasonable to stay 12 hours in an area where there is no restaurant, to say the least, thus a) either stamp the boarding pass for free or b) escort you in to the gates in the international area.