Bug: Python 3.13 REPL on Windows drops first items in print loop when using end=' '

[Nataliya3112]

In Python 3.13.9 on Windows, the REPL intermittently fails to print the first elements of a loop when using print(..., end=' ').

Expected output: 1 2 3 4 5

Actual output: 3 4 5

The issue does not occur in IDLE, only in the terminal REPL.

Steps to Reproduce:
1)Run in Windows terminal:
for i in [1,2,3,4,5]:
print(i, end=' ')

2)Observed output: 3 4 5

Environment: Python: 3.13.9 (tags/v3.13.9:8183fa5, Oct 14 2025, 14:09:13) [MSC v.1944 64 bit (AMD64)]
Platform: win32
OS: Windows-10-10.0.19045-SP0

Installed via: py -3.13 launcher
Behavior NOT observed in Python 3.11 or in IDLE.

Notes

Reproducible consistently

Only affects REPL output

Likely related to stdout buffering / console IO changes in Python 3.13 on Windows

print(i) (with newline) works correctly