Highest ODI score on debut?

[Ausathon]

Im well into the 2025/26 season on my England career and a young gun 24-year-old called Tom Treanor just slammed 146 in his first ODI match.

Is this some kind of record? Surely not. Is there anybody out there who has bettered this?

[Cam]

I had a bloke score 246 on debut in a test and 154 in the 2nd innings... which is a world record, (going by the current test records)
However, i was dumb enough not to save the file, i remember it coz i wanted to look it up!