[Feature Request] Add multi-language (i18n) support for CLI output, starting with Simplified Chi nese (zh-CN)

Feature Description

Currently, all CLI output, prompts, help documentation, and error messages in kimi-cli are in
English. While this is standard for many development tools, it creates a significant learning cu
rve and usability barrier for non-English speaking users, particularly the large community of Ch
inese-speaking developers.

Proposed Solution

I would like to propose adding internationalization (i18n) support to kimi-cli, with Sim
plified Chinese (zh-CN) as the first priority target language.

Implementation Suggestions:

1. Language Switching: Support runtime language switching via:

   • Environment variable: KIMI_CLI_LANG=zh_CN
   • Command-line flag: --lang zh_CN or -l zh_CN
   • Or automatically detect system locale (LANG / LC_ALL environment variables)

2. Scope of Localization: All user-facing strings should be translatable, including:

   • Command help text (kimi --help, subcommand help)
   • Interactive prompts and confirmations
   • Success / error / warning messages
   • Status indicators and progress messages
   • Menu titles and option labels

3. Translation Storage: Consider standard i18n frameworks or simple JSON/TOML translation fi
   les stored under a locales/ or i18n/ directory, allowing community contributions for additio
   nal languages over time.

Motivation / Use Case

As a CLI agent tool aiming to improve developer productivity, accessibility in the user's native
language greatly lowers the barrier to entry. Many successful CLI tools (e.g., npm, docker,
git in some distributions) provide localized output, which is especially helpful for:

• Beginners who are not fluent in English
• Teams who need to onboard members quickly
• Reducing cognitive load when reading error messages under time pressure

Example

Current behavior:

$ kimi --help
Usage: kimi [OPTIONS] [PROMPT]...

  Kimi Code CLI is your next CLI agent.

Options:
  --model, -m TEXT  Model to use
  --help            Show this message and exit.

Desired behavior (when KIMI_CLI_LANG=zh_CN or system locale is zh-CN):
$ kimi --help
用法: kimi [选项] [提示词]...

  Kimi Code CLI 是您的下一代命令行智能助手。

选项:
  --model, -m 文本  指定要使用的模型
  --help            显示此帮助信息并退出

Willingness to Contribute
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I and other community members would be happy to help provide and maintain the Simplified Chinese
translation files if the maintainers agree on the i18n architecture and direction.

Additional Context
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• Related keywords: i18n, l10n, internationalization, localization, 中文, Chinese, multilingual
• This request is about CLI output localization, not model language capabilities (the model alre
  y speaks Chinese perfectly).
Thank you for considering this feature request!

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Start with the kimi --help entry point and inventory how help text, prompts, errors, status messages, and option labels are produced. Resolve the language-selection mechanism and translation storage approach before implementing Simplified Chinese output; done means the stated user-facing CLI surfaces respond to KIMI_CLI_LANG=zh_CN, a language flag, or locale detection as agreed.