He moves to the National League side on a short-term deal until 4 January 2026.
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Johnson, 20, spent the latter part of the 2024-25 season on loan at Sky Bet League Two outfit Notts County.
Sunderland academy manager Robin Nicholls said: “This presents Zak with a great opportunity to build on his minutes in senior football.
"Having already spent time with Hartlepool, Dundalk, and most recently Notts County, this is a further chance for him to showcase his ability at a competitive level. We look forward to monitoring him closely in the National League.”