[FEATURE] i18n / localization support for CLI UI strings (permission prompts, menus)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet (only stale-closed ones exist — see Additional Context)
• [x] This is a single feature request (not multiple features)

Problem Statement

I configure Claude Code to respond in Japanese via my CLAUDE.md, and the model side works perfectly. However, the CLI's built-in UI — permission prompts, confirmation dialogs, menu options like "Yes / Yes, and don't ask again / No, and tell Claude what to do differently" — remains English-only.

This creates a confusing mixed-language experience: the model speaks fluent Japanese, but the interface that asks me critical permission questions speaks only English.

For non-native English speakers this is more than an annoyance:

• Each permission prompt requires mental translation, slowing the workflow
• There is a real risk of clicking the wrong option because the difference between options like "Yes, and don't ask again for X" vs "No, and tell Claude what to do differently" is subtle and easy to miss in a foreign language
• The prompts grant permissions — getting them wrong has security implications

This noticeably impacts daily productivity for users working primarily in non-English languages.

Proposed Solution

Add i18n support for CLI UI strings:

1. Locale setting in ~/.claude/settings.json, e.g. "locale": "ja"
2. Auto-detection from the LANG environment variable as a fallback
3. Phased rollout — start with the highest-impact strings (permission dialogs, confirmation prompts) and expand to menus, status messages, and the rest of the TUI
4. Provide official translations for at least: Japanese (ja), Simplified Chinese (zh-CN), Traditional Chinese (zh-TW), Korean (ko), Spanish (es), French (fr), German (de)
5. Open the translation strings to community contribution (e.g. via Crowdin or simple JSON files in the repo)

Alternative Solutions

• The community has built claude-code-i18n (https://github.com/joshchaotang/claude-code-i18n), a client-side patcher for zh-TW / zh-CN. The fact that this exists is itself evidence of demand. However:
• It does not support Japanese
• Client-side patching is fragile across Claude Code versions
• Official support would be more reliable, discoverable, and accessible to all non-English users

• Current personal workaround: I have to mentally translate every permission prompt, or pre-allowlist domains/commands to avoid the prompt entirely — but the latter reduces the safety value of the prompts.

Priority

High - Significant impact on productivity

Feature Category

Interactive mode (TUI)

Use Case Example

A concrete daily scenario from a Japanese user:

1. My CLAUDE.md instructs Claude to respond in Japanese — Claude speaks fluent Japanese
2. Claude needs to fetch a URL (e.g. a README from raw.githubusercontent.com)
3. Claude Code shows the prompt:

Fetch
  https://raw.githubusercontent.com/.../README.md
  Claude wants to fetch content from raw.githubusercontent.com

Do you want to allow Claude to fetch this content?
> 1. Yes
  2. Yes, and don't ask again for raw.githubusercontent.com
  3. No, and tell Claude what to do differently (esc)

1. The user — who is otherwise comfortable using Claude in Japanese — has to mentally translate this every time. Subtle distinctions (e.g. between options 2 and 3) require careful reading
2. After dozens of these per day, the friction is significant. And if the user misclicks, they may grant a permission they did not intend, or reject one they meant to allow

A localized prompt would look like:

取得
  https://raw.githubusercontent.com/.../README.md
  Claude が raw.githubusercontent.com からコンテンツの取得を求めています

このコンテンツの取得を許可しますか？
> 1. はい
  2. はい、raw.githubusercontent.com には今後確認しない
  3. いいえ、別の方法を Claude に指示する (esc)

This single change would meaningfully improve the experience for the entire non-English user base.

Additional Context

This feature has been requested at least five times before, and every single one was closed by the stale bot due to inactivity — not rejected on merits:

| # | Title | Closed reason |
|---|-------|---------------|
| #33329 | Feature request: i18n support for permission prompts and UI messages | stale (April 2026) |
| #43934 | Feature Request: i18n / Localization support for UI strings | duplicate of #33329 |
| #34381 | Feature Request: i18n/Localization support for CLI UI strings | duplicate |
| #22386 | Feature Request: i18n support for built-in UI elements | duplicate |
| #18362 | Feature Request: Add localization/i18n support for UI messages | duplicate |

The closing comment on #33329 from github-actions explicitly says:

Closing for now — inactive for too long. Please open a new issue if this is still relevant.

I am opening this fresh issue per that guidance. The recurring submissions over more than three months indicate a persistent and growing community need.

Related community work:

• claude-code-i18n: https://github.com/joshchaotang/claude-code-i18n (client-side translation patches for zh-TW / zh-CN — proves the demand and approach)

Thank you for considering this. I am happy to help test localizations or contribute Japanese translations once a translation pipeline exists.