Aug 2023 or Aug 2022?
If PD was Aug 8 2023, was approved Dec 8, 2023, and he turned 19 on Sept 1, 2023 (for example), then his CSPA age will be 21 in Jan 1, 2026.
If PD was Aug 8, 2022, was approved Dec 8, 2023, and he turned 19 on July 1, 2023 (for 2nd example), then his CSPA age 21 will be Nov 1, 2026.
Basically, his age minus the time it took to approve the I-130. USCIS did him no favors by approving the I-130 quickly.
Currently F2A final action date is Feb 2019. If the PD is Aug 2022, there is a small chance it will be current by Nov 2026 in the 2nd example above.
If the PD is Aug 2023, he will age out.