Speculators turned net long yen for the first time since February.
The positioning swing was abrupt: more than 92,000 net short contracts became 10,796 net long in one week.
A stronger yen matters outside Japan because it is deeply embedded in global carry trades; sustained appreciation can force leveraged investors to unwind positions elsewhere.
CFTC data show a dramatic weekly reversal from more than 92,000 net short contracts to 10,796 net long.