kimi web crashes at startup on Windows when stdout is redirected: UnicodeEncodeError (gbk) in print_banner

Bug description

kimi web crashes immediately at startup on Chinese-locale Windows when its stdout is redirected (pipe/file) or when it is launched by a parent process that captures stdout. The crash happens while printing the startup banner: the ➜ (U+279C) character cannot be encoded with the locale codec (GBK / cp936), and the unhandled UnicodeEncodeError kills the whole process before the HTTP server binds its port.

As a result, the web server never starts, and a Web UI page already open in the browser shows repeated "实时连接出错 / WebSocket error" toasts because nothing is listening.

Environment

• OS: Windows 11 (10.0.26100), Simplified Chinese locale (ANSI codepage 936 / GBK)
• Kimi Code CLI: v0.28.1, native win32-x64 build (bundled with VS Code extension moonshot-ai.kimi-code, kimi_cli 1.43.0, PyInstaller / Python 3.14)

Steps to reproduce

1. On a Chinese-locale Windows machine, redirect stdout, e.g.:

   kimi.exe web --port 58627 --no-open > web.log 2>&1
   

   (or launch kimi web from any parent process that pipes stdout)
2. The process exits immediately; the port is never bound.

Actual behavior

Traceback (most recent call last):
  ...
  in web:70
  in run_web_server:437
  in print_banner:118
UnicodeEncodeError: 'gbk' codec can't encode character '➜' in position 4:
illegal multibyte sequence
[PYI-xxxxx:ERROR] Failed to execute script '__main__' due to unhandled exception!

Expected behavior

Banner printing should never crash the server. Please make print_banner encoding-safe (e.g. write with errors="replace", force UTF-8, or drop non-encodable characters) so kimi web starts regardless of stdout encoding / console availability.

What does NOT help

chcp 65001, PYTHONUTF8=1, and PYTHONIOENCODING=utf-8 all fail to prevent the crash when stdout is redirected (verified on v0.28.1).

Workaround

Run kimi web attached to a real console window (cmd / PowerShell / Windows Terminal) and keep that window open — console I/O uses UTF-8 (PEP 528), so the banner prints fine and the server starts normally.

Start by locating the print_banner entry point mentioned in the traceback and trace how it is called from run_web_server. Reproduce kimi web with stdout redirected under a non-UTF-8 Windows locale, then verify that the banner no longer raises UnicodeEncodeError and the server binds its port.