Birmingham midfielder Charlee Adams has signed a new one-year contract with the club.
Southampton are confident Jay Rodriguez will commit to a new long-term deal but the player will consider his options.
The Ghana World Cup player will spend this season on loan in Glasgow, and Celtic have the option to make it a permanent transfer next summer.
Wakaso, who has also played for Spanish clubs Espanyol, Villarreal and Elche, has 19 international caps and featured against Germany and Portugal in Brazil this summer.
The 24-year-old will be available for Saturday's Scottish Premiership trip to Dundee.