The bot-chat delivery child is guaranteed UTF-8 on Windows (hermes_cli
reconfigures its streams via hermes_bootstrap even under
PYTHONIOENCODING=cp1252), but the gateway parent is not started in UTF-8
mode — its env overlay sets only PYTHONIOENCODING, which rebinds the
parent's own streams but does not change the locale codec text=True picks.
The delivery pipes were therefore decoded with the ANSI code page (cp1252):
an accented reply came back mojibake'd, and bytes undefined in cp1252
killed the reader thread, losing the captured reply and the failure
diagnostic while the delivery still booked as delivered (#115894).
Pin encoding='utf-8' on the win32 branch only — on POSIX the child keeps
the locale codec, so the locale default stays correct there (#66566) —
mirroring the win32 branch of the no_agent script lane (#45099).
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