@@ -79,6 +79,8 @@ story("derives each block direction from the language it is mostly written in",
       "<p>سأستخدم React في المشروع</p>",
       "<p>React هو مكتبة واجهة برمجية.</p>",
       "<p>Use React in the project.</p>",
+      "<p>这是一个测试 مرحبا</p>",
+      "<p>यह एक परीक्षण है مرحبا</p>",
       "<p>سأستخدم <code>npm install</code> هنا</p>",
       "<ul><li>سأستخدم npm install في المشروع</li><li>Use the CLI</li></ul>",
       "<table><thead><tr><th>الاسم</th><th>القيمة</th></tr></thead></table>",
@@ -90,6 +92,8 @@ story("derives each block direction from the language it is mostly written in",
     '<p dir="rtl">سأستخدم React في المشروع</p>',
     '<p dir="rtl">React هو مكتبة واجهة برمجية.</p>',
     '<p dir="ltr">Use React in the project.</p>',
+    '<p dir="ltr">这是一个测试 مرحبا</p>',
+    '<p dir="ltr">यह एक परीक्षण है مرحبا</p>',
     '<p dir="rtl">سأستخدم <code>npm install</code> هنا</p>',
     '<ul dir="rtl"><li dir="rtl">سأستخدم npm install في المشروع</li><li dir="ltr">Use the CLI</li></ul>',
     '<table dir="rtl"><thead><tr><th dir="rtl">الاسم</th><th dir="rtl">القيمة</th></tr></thead></table>',
@@ -124,43 +128,20 @@ for (const streaming of [false, true]) {
       const paragraphs = markdown.locator("p")
       await expect(paragraphs).toHaveCount(3)
 
-      // The first logical word of a right-to-left paragraph sits right of the last one.
-      const layout = await paragraphs.evaluateAll((elements) =>
-        elements.map((element) => {
-          const walker = document.createTreeWalker(element, NodeFilter.SHOW_TEXT)
-          const words: { left: number; top: number }[] = []
-
-          for (let node = walker.nextNode(); node; node = walker.nextNode()) {
-            const text = node.nodeValue ?? ""
-            let offset = 0
-
-            for (const part of text.split(/(\s+)/)) {
-              if (part.trim()) {
-                const range = document.createRange()
-                range.setStart(node, offset)
-                range.setEnd(node, offset + part.length)
-                const box = range.getBoundingClientRect()
-                words.push({ left: box.left, top: box.top })
-              }
-
-              offset += part.length
-            }
-          }
-
-          const firstLine = words.filter((word) => Math.abs(word.top - words[0].top) < 10)
-
-          return {
-            dir: element.getAttribute("dir"),
-            direction: getComputedStyle(element).direction,
-            firstOnRight: firstLine[0].left > firstLine[firstLine.length - 1].left,
-          }
-        }),
+      // The direction each block computes decides how the bidi algorithm
+      // orders the words inside it.
+      const blocks = await markdown.locator("h2, p").evaluateAll((elements) =>
+        elements.map((element) => ({
+          dir: element.getAttribute("dir"),
+          direction: getComputedStyle(element).direction,
+        })),
       )
 
-      expect(layout).toEqual([
-        { dir: "rtl", direction: "rtl", firstOnRight: true },
-        { dir: "rtl", direction: "rtl", firstOnRight: true },
-        { dir: "ltr", direction: "ltr", firstOnRight: false },
+      expect(blocks).toEqual([
+        { dir: "ltr", direction: "ltr" },
+        { dir: "rtl", direction: "rtl" },
+        { dir: "rtl", direction: "rtl" },
+        { dir: "ltr", direction: "ltr" },
       ])
     },
   )
 
@@ -129,38 +129,27 @@ story("keeps patch file disclosures independent", async ({ mount }) => {
   await expect(deleted).toHaveAttribute("aria-expanded", "false")
 })
 
-story("keeps an Arabic prompt right-to-left when it starts with a Latin word", async ({ mount }) => {
+story("keeps each prompt line in the direction it is mostly written in", async ({ mount }) => {
   const root = await mount("current-session-timeline-rows--arabic-prompt")
-  const text = root.locator('[data-slot="user-message-text"]')
-  await expect(text).toHaveAttribute("dir", "rtl")
-  expect(await text.evaluate((element) => getComputedStyle(element).direction)).toBe("rtl")
-
-  // The first logical word of a right-to-left prompt sits right of the last one.
-  const order = await text.evaluate((element) => {
-    const walker = document.createTreeWalker(element, NodeFilter.SHOW_TEXT)
-    const words: { left: number; top: number }[] = []
-
-    for (let node = walker.nextNode(); node; node = walker.nextNode()) {
-      const value = node.nodeValue ?? ""
-      let offset = 0
-
-      for (const part of value.split(/(\s+)/)) {
-        if (part.trim()) {
-          const range = document.createRange()
-          range.setStart(node, offset)
-          range.setEnd(node, offset + part.length)
-          const box = range.getBoundingClientRect()
-          words.push({ left: box.left, top: box.top })
-        }
-
-        offset += part.length
-      }
-    }
-
-    const firstLine = words.filter((word) => Math.abs(word.top - words[0].top) < 10)
-
-    return { first: firstLine[0].left, last: firstLine[firstLine.length - 1].left }
-  })
-
-  expect(order.first).toBeGreaterThan(order.last)
+  const bubbles = root.locator('[data-slot="user-message-text"]')
+  await expect(bubbles).toHaveCount(2)
+
+  // The prompt opens with "React", so the first strong character is Latin while
+  // the sentence is mostly Arabic.
+  await expect(bubbles.first()).toHaveAttribute("dir", "rtl")
+  expect(await bubbles.first().evaluate((element) => getComputedStyle(element).direction)).toBe("rtl")
+
+  const lines = bubbles.nth(1).locator('[data-slot="user-message-line"]')
+  await expect(lines).toHaveCount(2)
+  expect(
+    await lines.evaluateAll((elements) =>
+      elements.map((element) => ({
+        dir: element.getAttribute("dir"),
+        direction: getComputedStyle(element).direction,
+      })),
+    ),
+  ).toEqual([
+    { dir: "ltr", direction: "ltr" },
+    { dir: "rtl", direction: "rtl" },
+  ])
 })
@@ -184,6 +184,10 @@
       transition: none;
     }
 
+    [data-slot="user-message-line"] {
+      unicode-bidi: isolate;
+    }
+
     [data-highlight="file"],
     [data-highlight="agent"] {
       color: inherit;
 
@@ -0,0 +1,27 @@
+import { describe, expect, test } from "bun:test"
+import { textDirection } from "./text-direction"
+
+describe("textDirection", () => {
+  test("follows the language most of the text is written in", () => {
+    expect(textDirection("React هو مكتبة واجهة برمجية")).toBe("rtl")
+    expect(textDirection("سأستخدم React في المشروع")).toBe("rtl")
+    expect(textDirection("Use React in the project")).toBe("ltr")
+  })
+
+  test("keeps left-to-right scripts outside the rtl set", () => {
+    expect(textDirection("这是一个测试 مرحبا")).toBe("ltr")
+    expect(textDirection("これはテストです مرحبا")).toBe("ltr")
+    expect(textDirection("यह एक परीक्षण है مرحبا")).toBe("ltr")
+    expect(textDirection("한국어 테스트 مرحبا")).toBe("ltr")
+  })
+
+  test("treats digits and punctuation as neutral", () => {
+    expect(textDirection("1234 (5%) -- 6.")).toBeUndefined()
+    expect(textDirection("مرحبا 1234")).toBe("rtl")
+  })
+
+  test("leaves a tie to the ambient direction", () => {
+    expect(textDirection("مرحبا hello")).toBeUndefined()
+    expect(textDirection("")).toBeUndefined()
+  })
+})
@@ -1,18 +1,21 @@
-// Right-to-left scripts: Hebrew, Arabic, Syriac, Thaana, NKo, Samaritan, Mandaic.
-const rightToLeftScript = /[\u0590-\u08ff\ufb1d-\ufdff\ufe70-\ufeff]/g
+// Letters decide direction; digits, punctuation and whitespace are neutral.
+const letter = /\p{L}/gu
 
-// Left-to-right scripts that carry letters: Latin, Greek, Cyrillic.
-const leftToRightScript = /[a-z\u00c0-\u00d6\u00d8-\u00f6\u00f8-\u02af\u0370-\u03ff\u0400-\u04ff\u1e00-\u1eff]/gi
+// Scripts written right to left. A letter in any other script reads left to right.
+const rightToLeft = /(?=[\p{Script=Arabic}\p{Script=Hebrew}\p{Script=Syriac}\p{Script=Thaana}\p{Script=Nko}\p{Script=Samaritan}\p{Script=Mandaic}\p{Script=Adlam}])\p{L}/gu
 
 /**
  * `dir="auto"` resolves from the first strong character, which flips a mostly
- * Arabic text that opens with an identifier such as "React". Counting both
+ * Arabic text that opens with an identifier such as "React". Counting the
  * scripts and keeping the majority holds the text in the language it is mostly
- * written in. Digits and punctuation are neutral and decide nothing.
+ * written in. Counting every letter rather than a list of left-to-right scripts
+ * keeps Chinese, Japanese, Korean, Devanagari and other left-to-right writing
+ * systems left to right when a single right-to-left word appears.
  */
 export function textDirection(text: string) {
-  const rtl = text.length - text.replace(rightToLeftScript, "").length
-  const ltr = text.length - text.replace(leftToRightScript, "").length
+  const letters = text.match(letter)?.length ?? 0
+  const rtl = text.match(rightToLeft)?.length ?? 0
+  const ltr = letters - rtl
 
   if (rtl === ltr) return
 
 
@@ -528,7 +528,9 @@ function CurrentHighlightedText(props: {
   files: PromptFileAttachment[]
   agents: PromptAgentAttachment[]
 }) {
-  const segments = createMemo(() => {
+  // A prompt can switch language line by line, so each line resolves its own
+  // direction instead of inheriting one answer for the whole message.
+  const lines = createMemo(() => {
     const references = [
       ...props.files.flatMap((file) =>
         file.mention ? [{ start: file.mention.start, end: file.mention.end, type: "file" as const }] : [],
@@ -538,30 +540,50 @@ function CurrentHighlightedText(props: {
       ),
     ].sort((a, b) => a.start - b.start)
 
-    const result: HighlightSegment[] = []
+    const segments: HighlightSegment[] = []
     let last = 0
     references.forEach((reference) => {
       if (reference.start < last) return
 
-      if (reference.start > last) result.push({ text: props.text.slice(last, reference.start) })
-      result.push({ text: props.text.slice(reference.start, reference.end), type: reference.type })
+      if (reference.start > last) segments.push({ text: props.text.slice(last, reference.start) })
+      segments.push({ text: props.text.slice(reference.start, reference.end), type: reference.type })
       last = reference.end
     })
 
-    if (last < props.text.length) result.push({ text: props.text.slice(last) })
+    if (last < props.text.length) segments.push({ text: props.text.slice(last) })
 
-    return result
+    return segments.reduce<HighlightSegment[][]>(
+      (lines, segment) => {
+        segment.text.split("\n").forEach((text, index) => {
+          if (index > 0) lines.push([])
+
+          if (text) lines[lines.length - 1].push({ text, type: segment.type })
+        })
+
+        return lines
+      },
+      [[]],
+    )
   })
 
   return (
-    <For each={segments()}>
-      {(segment) => (
-        <span data-highlight={segment.type}>
-          <Show when={segment.type && segment.text.startsWith("@")} fallback={segment.text}>
-            <span data-slot="user-message-mention-prefix">@</span>
-            {segment.text.slice(1)}
-          </Show>
-        </span>
+    <For each={lines()}>
+      {(line, index) => (
+        <>
+          {index() > 0 ? "\n" : ""}
+          <span data-slot="user-message-line" dir={textDirection(line.map((segment) => segment.text).join(""))}>
+            <For each={line}>
+              {(segment) => (
+                <span data-highlight={segment.type}>
+                  <Show when={segment.type && segment.text.startsWith("@")} fallback={segment.text}>
+                    <span data-slot="user-message-mention-prefix">@</span>
+                    {segment.text.slice(1)}
+                  </Show>
+                </span>
+              )}
+            </For>
+          </span>
+        </>
       )}
     </For>
   )
 
@@ -1112,6 +1112,7 @@ export const arabicPromptDocument = document([
     completed: 92_500,
     content: [{ type: "text", text: "تمام. سأشرح الخطوات بالترتيب." }],
   }),
+  user("msg_user_multiline", "Fix the login bug please\nمرحبا كيف حالك؟ سأراجع الكود الآن.", 93_000),
 ])
 
 export const attachmentsAndCommentsPresentation = {