CjkLineBreak [rule] v1.0.0

CJK (Chinese/Japanese/Korean) text must use language-aware line-breaking rules. CSS line-break and word-break properties have language-specific semantics that change which characters may start or end a line (kinsoku shori in Japanese).

Containers that may render CJK text MUST set lang correctly on the HTML element (lang='ja', 'zh-Hans', 'zh-Hant', 'ko') and use line-break: strict (or normal with explicit word-break: keep-all where words must not split). Never apply Latin-only word-break: break-all to CJK content — it produces grammatically broken lines that violate JIS X 4051 / GB/T 15834 rules. For mixed Latin+CJK, prefer overflow-wrap: anywhere on Latin tokens only or use <bdi> boundaries.

Applies To

• Any product surface that renders CJK content (zh, ja, ko)
• User-generated content (comments, posts) that may contain CJK
• Translation files containing CJK target locales
• Text in fixed-width containers (cards, table cells, sidebars)
• Email templates and PDF exports rendered with CSS

Implementation Checklist

• Root reflects active locale; switching languages updates lang attribute
• CJK locales set CSS line-break: strict and word-break: normal (NOT break-all)
• Mixed Latin+CJK tokens use overflow-wrap: anywhere only on Latin substrings via
• Test fixtures include lines ending in 「 and lines starting with 。 — visual regression must catch kinsoku violations
• Hyphenation (hyphens: auto) is meaningless for CJK; do not enable for CJK locales

Severity

warn

Counter Examples

• こんにちは、世界
  — breaks between any two characters including immediately before 、 and after 「, violating kinsoku.
• Missing lang attribute defaults to lang='en' even when content is Chinese — browser uses Latin breaking rules; no kinsoku enforcement.
• overflow-wrap: anywhere applied globally — Latin URL fragments break correctly, but CJK punctuation now appears at line starts.

CjkLineBreak [rule] v1.0.0

CJK (Chinese/Japanese/Korean) text must use language-aware line-breaking rules. CSS line-break and word-break properties have language-specific semantics that change which characters may start or end a line (kinsoku shori in Japanese).

Containers that may render CJK text MUST set lang correctly on the HTML element (lang='ja', 'zh-Hans', 'zh-Hant', 'ko') and use line-break: strict (or normal with explicit word-break: keep-all where words must not split). Never apply Latin-only word-break: break-all to CJK content — it produces grammatically broken lines that violate JIS X 4051 / GB/T 15834 rules. For mixed Latin+CJK, prefer overflow-wrap: anywhere on Latin tokens only or use <bdi> boundaries.

Applies To

• Any product surface that renders CJK content (zh, ja, ko)
• User-generated content (comments, posts) that may contain CJK
• Translation files containing CJK target locales
• Text in fixed-width containers (cards, table cells, sidebars)
• Email templates and PDF exports rendered with CSS

Implementation Checklist

• Root reflects active locale; switching languages updates lang attribute
• CJK locales set CSS line-break: strict and word-break: normal (NOT break-all)
• Mixed Latin+CJK tokens use overflow-wrap: anywhere only on Latin substrings via
• Test fixtures include lines ending in 「 and lines starting with 。 — visual regression must catch kinsoku violations
• Hyphenation (hyphens: auto) is meaningless for CJK; do not enable for CJK locales

Severity

warn

Counter Examples

• こんにちは、世界
  — breaks between any two characters including immediately before 、 and after 「, violating kinsoku.
• Missing lang attribute defaults to lang='en' even when content is Chinese — browser uses Latin breaking rules; no kinsoku enforcement.
• overflow-wrap: anywhere applied globally — Latin URL fragments break correctly, but CJK punctuation now appears at line starts.

Examples

• Japanese paragraph:

  — closing 」 stays glued to preceding character; opening 「 stays glued to following character.

• Simplified Chinese card: lang='zh-Hans'; word-break: normal; line-break: strict. Long English URL inside: wrap with .
• Korean (lang='ko'): same kinsoku rules apply; spaces between eojeol are honored — word-break: keep-all prevents breaking within a word.

Relations

enhances: @community/rule-intl-api-locale-formatting

Rationale

CJK has no inter-word spaces; line-breaking is character-by-character constrained by punctuation rules (kinsoku shori). Closing punctuation (。、」』) must NEVER start a line; opening punctuation (「『) must NEVER end a line. The CSS line-break: strict engine encodes JIS X 4051; loose is acceptable for narrow columns; anywhere is forbidden for body text. Browsers fall back to language-specific rules only when lang is set — defaulting to lang='en' produces visibly broken Japanese paragraphs.

Applies To

• Any product surface that renders CJK content (zh, ja, ko)
• User-generated content (comments, posts) that may contain CJK
• Translation files containing CJK target locales
• Text in fixed-width containers (cards, table cells, sidebars)
• Email templates and PDF exports rendered with CSS

Implementation Checklist

• Root reflects active locale; switching languages updates lang attribute
• CJK locales set CSS line-break: strict and word-break: normal (NOT break-all)
• Mixed Latin+CJK tokens use overflow-wrap: anywhere only on Latin substrings via
• Test fixtures include lines ending in 「 and lines starting with 。 — visual regression must catch kinsoku violations
• Hyphenation (hyphens: auto) is meaningless for CJK; do not enable for CJK locales

Severity

warn

Counter Examples

• こんにちは、世界
  — breaks between any two characters including immediately before 、 and after 「, violating kinsoku.
• Missing lang attribute defaults to lang='en' even when content is Chinese — browser uses Latin breaking rules; no kinsoku enforcement.
• overflow-wrap: anywhere applied globally — Latin URL fragments break correctly, but CJK punctuation now appears at line starts.

Enhances

@community/rule-intl-api-locale-formatting