feat(tui): RTL/Bidi support for Persian, Arabic, Hebrew, and Urdu text

ui-tui/src/__tests__/text.test.ts

@@ -9,6 +9,7 @@ import {
   estimateTokensRough,
   fmtK,
   hasAnsi,
+  isRtl,
   isToolTrailResultLine,
   lastCotTrailIndex,
   parseToolTrailResultLine,
@@ -254,3 +255,47 @@ describe('estimateRows', () => {
     expect(estimateRows(snake, w)).toBe(estimateRows(plain, w))
   })
 })
+
+describe('isRtl', () => {
+  it('returns false for empty string', () => {
+    expect(isRtl('')).toBe(false)
+  })
+
+  it('returns false for LTR English text', () => {
+    expect(isRtl('Hello world')).toBe(false)
+  })
+
+  it('returns false for LTR Chinese text', () => {
+    expect(isRtl('你好世界')).toBe(false)
+  })
+
+  it('detects Persian text', () => {
+    expect(isRtl('سلام دنیا')).toBe(true)
+  })
+
+  it('detects Arabic text', () => {
+    expect(isRtl('مرحبا بالعالم')).toBe(true)
+  })
+
+  it('detects Hebrew text', () => {
+    expect(isRtl('שלום עולם')).toBe(true)
+  })
+
+  it('detects Urdu text (Arabic script)', () => {
+    expect(isRtl('ہیلو دنیا')).toBe(true)
+  })
+
+  it('detects RTL after leading whitespace', () => {
+    expect(isRtl('   مرحبا')).toBe(true)
+  })
+
+  it('returns false for LTR text with trailing RTL', () => {
+    // First strong character is LTR
+    expect(isRtl('Hello مرحبا')).toBe(false)
+  })
+
+  it('strips ANSI before detection', () => {
+    // \x1b[31m is red color ANSI code — the first real char is Arabic
+    expect(isRtl('\x1b[31mمرحبا\x1b[0m')).toBe(true)
+  })
+})

ui-tui/src/components/messageLine.tsx

@@ -13,6 +13,7 @@ import {
   compactPreview,
   hasAnsi,
   isPasteBackedText,
+  isRtl,
   sanitizeAnsiForRender,
   stripAnsi
 } from '../lib/text.js'
@@ -193,6 +194,7 @@ export const MessageLine = memo(function MessageLine({
   // segments) keep a blank line on both sides so the patch doesn't butt up
   // against the prose around it.
   const isDiffSegment = msg.kind === 'diff'
+  const rtl = isRtl(msg.text)
 
   return (
     <Box
@@ -226,14 +228,23 @@ export const MessageLine = memo(function MessageLine({
         </Box>
       )}
 
-      <Box>
-        <NoSelect flexShrink={0} fromLeftEdge width={gutterWidth}>
+      <Box flexDirection={rtl ? 'row-reverse' : 'row'}>
+        <NoSelect
+          flexShrink={0}
+          {...(rtl ? {} : { fromLeftEdge: true })}
+          width={gutterWidth}
+        >
           <Text bold={msg.role === 'user'} color={prefix}>
             {glyph}{' '}
           </Text>
         </NoSelect>
 
-        <Box width={transcriptBodyWidth(cols, msg.role, t.brand.prompt, TERMUX_TUI_MODE)}>{content}</Box>
+        <Box
+          width={transcriptBodyWidth(cols, msg.role, t.brand.prompt, TERMUX_TUI_MODE)}
+          alignItems={rtl ? 'flex-end' : 'flex-start'}
+        >
+          {content}
+        </Box>
       </Box>
     </Box>
   )

ui-tui/src/lib/text.ts

@@ -364,3 +364,29 @@ export const pick = <T>(a: T[]) => a[Math.floor(Math.random() * a.length)]!
 
 export const isPasteBackedText = (text: string) =>
   /\[\[paste:\d+(?:[^\n]*?)\]\]|\[paste #\d+ (?:attached|excerpt)(?:[^\n]*?)\]/.test(text)
+
+/**
+ * First-strong-character RTL detection (matches CSS direction: auto behaviour).
+ * Returns true when the first non-whitespace code point falls in an RTL
+ * script range: Hebrew (0590–05FF), Arabic/Persian (0600–06FF),
+ * Arabic Supplement (0750–077F), Arabic Extended-A (08A0–08FF),
+ * Arabic Presentation Forms (FB50–FDFF, FE70–FEFF).
+ */
+export const isRtl = (text: string): boolean => {
+  if (!text) return false
+  const clean = stripAnsi(text)
+  for (let i = 0; i < clean.length; i++) {
+    const cp = clean.codePointAt(i)!
+    // Skip whitespace / control chars
+    if (cp <= 0x20 || (cp >= 0x09 && cp <= 0x0D)) continue
+    return (
+      (cp >= 0x0590 && cp <= 0x05FF) ||
+      (cp >= 0x0600 && cp <= 0x06FF) ||
+      (cp >= 0x0750 && cp <= 0x077F) ||
+      (cp >= 0x08A0 && cp <= 0x08FF) ||
+      (cp >= 0xFB50 && cp <= 0xFDFF) ||
+      (cp >= 0xFE70 && cp <= 0xFEFF)
+    )
+  }
+  return false
+}