Sam, who has captained England at U17 level, made his full debut for Newcastle’s U21s side during an EFL Trophy clash against League Two Harrogate Town in November 2025.
Reflecting on his full U21s bow earlier this month, Alabi said: "I've challenged myself at different levels this season so I think this is another step to what I want to pursue. I was very pleased to play the full game, especially against a League Two side.
"This is another milestone in my career so far. I've achieved many good things during my time at Newcastle so this was another; a very good opportunity and learning curve."
Sam was named in a senior matchday squad for the first time during November's UEFA Champions League group-phase clash away at Olympique de Marseille and targets a senior debut for Eddie Howe's side.
On his 17th birthday, Sam committed his future with the Magpies after putting pen to paper on a first professional contract.
