The Brazil international's agent, Kia Joorabchian, revealed on Tuesday's White and Jordan show that Coutinho was called by new Barca boss Koeman the day after Bayern Munich won the Champions League to be told he would be in his squad for the 2020/21 campaign.
Coutinho spent last season on loan in Bavaria, winning a treble, and he even scored twice in Bayern's 8-2 thrashing of his parent club in the European Cup.
The former Liverpool ace was expected to leave Camp Nou on a permanent basis this summer following the expiration of his loan in Germany, with Arsenal, Tottenham and Leicester all linked with bringing Coutinho back to the Premier League
But he was contacted by Koeman - who replaced Quique Setien as Barca manager - to be told he is remaining in Catalonia, and he's fit and raring to go with Barcelona beginning their LaLiga campaign later this month.
Asked if Coutinho will stay at Barcelona this summer, super agent Joorabchian told talkSPORT host Jim White: "Yeah.
"Koeman called him right after the Champions League victory with Bayern, the following day, and told him he's very much in his plans and would like him to return.
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"He was due to return on September 7 but actually he returned at the beginning of September because he didn't want to lose his momentum and fitness, and he's been training with Barcelona.
"All signs point to the fact Barcelona have changed quite dramatically, the way their philosophy of how they wanted to move forward from last year and the players they've brought in, like Coutinho, Dembele and Griezmann they're all going to be part of the squad this year."
Asked if Coutinho is gutted he scored to help knock the Catalans out the Champions League on the way to Bayern's European triumph, Joorabchian added: "Well, you've got to do your job and he did his job perfectly, and it's probably the reason why Barcelona want him back so badly."
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It appears Philippe Coutinho will not be sealing a Premier League return this summer as he is part of Ronald Koeman's Barcelona plans, talkSPORT has been told.