Every string the window, the panel and the menus have in Chinese now has a Japanese one too: 2917 entries in I18N.ja, translated to one glossary (プロバイダ, エージェント, ゲートウェイ, ルーティンググループ, 使用量, サインイン…), each keeping its {placeholders}, tags and leading spaces. Language takes "ja" (settings.Langs); System picks ja when navigator.language starts with ja, and <html lang> is ja-JP so CJK text draws in Japanese glyphs. Dates and numbers format through intlLang() (zh-CN or ja-JP) where they said zh-CN only. The tray menu, the quota alerts (7 日枠を 80% 使用、明日 14:30 にリセット) and the restart-to-update item have Japanese of their own (trayLang reads ja from the setting or a ja_JP/ja-JP system). Release notes stay English for ja, as the site has them in en and zh. The 万/亿 units option stays Chinese only.
Looked at in the Omarchy VM (magpie web, tokyo-night, ?locale=ja): Agents, Providers' Add sheet, a link's import, Routing, Usage, Gateway, Settings and the panel read in Japanese with nothing cut or overflowing. gui-ja.test.cjs (every zh key has a ja one with the same placeholders and tags; ja picked, a ja-JP system, en and zh systems, on WebKit and Chromium) and the ja cases in TestTrayMenuLabels and TestAlertText fail on the old code. On WebKit the other GUI tests fail as on the base but mobile-web's desktop comparison with origin/main, whose Settings now has a fourth language. go vet, builds (darwin, GOOS=linux nogui, GOOS=windows) and go test -tags nogui -count=1 ./... under a temp HOME pass.