From 6c00077d3838c1996e361e577b0064214fc07027 Mon Sep 17 00:00:00 2001
From: Brooklyn Nicholson <brooklyn.bb.nicholson@gmail.com>
Date: Thu, 11 Jun 2026 21:04:38 -0500
Subject: [PATCH] feat(desktop): auto-detect RTL/bidi text direction in chat

Arabic/Hebrew/Persian/Urdu chat text rendered left-to-right and
left-aligned, and mixed RTL/English technical messages (the common case)
read backwards. Resolve each chat block's base direction from its own
first strong character (UAX#9) with pure CSS, scoped to the chat
surfaces only:

- `unicode-bidi: plaintext` + `text-align: start` on assistant prose
  blocks (p, h1-h6, li, blockquote), the user bubble's text lines, and
  both composers (main + edit share the composer-rich-input slot). RTL
  blocks read and right-align RTL; English stays LTR; mixed
  conversations resolve per block. `text-align: start` is required
  because the user bubble hardcodes `text-left`.
- Inline `code` and KaTeX are pinned `direction: ltr; unicode-bidi:
  isolate`, so the bidi first-strong heuristic skips them: a sentence
  that *starts* with a command (`./run.sh ...`) followed by Arabic
  still resolves RTL, and the command's own neutrals keep their order.
- Fenced code surfaces (code-card, user fences) are pinned LTR so they
  never mirror or right-align inside an RTL list item or blockquote.

`direction` is never forced, so app chrome, layout, and list indent
stay LTR per the issue's request not to flip the whole UI. English-only
content is byte-for-byte unchanged.

Salvaged and unified from #44065 and #44169; verified in Chromium that
isolate removes inline code from the paragraph direction vote (the
code-first case), making the JS dir-resolution in #44065 unnecessary.

Fixes #44150

Co-authored-by: Adolanium <Adolanium@users.noreply.github.com>
Co-authored-by: Adalsteinn Helgason <AIalliAI@users.noreply.github.com>
---
 .../assistant-ui/user-message-text.tsx        |  4 ++-
 apps/desktop/src/styles.css                   | 31 +++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/apps/desktop/src/components/assistant-ui/user-message-text.tsx b/apps/desktop/src/components/assistant-ui/user-message-text.tsx
index 9e0da646f29..4235f94bf69 100644
--- a/apps/desktop/src/components/assistant-ui/user-message-text.tsx
+++ b/apps/desktop/src/components/assistant-ui/user-message-text.tsx
@@ -127,7 +127,9 @@ const InlineSegmentView: FC<{ text: string }> = ({ text }) => {
   const nodes = useMemo(() => splitInlineCode(text), [text])
 
   return (
-    <span className="wrap-anywhere block whitespace-pre-line">
+    // styles.css bidi hook (#44150); whitespace-pre-line makes each line its own
+    // UAX#9 paragraph so it resolves direction independently.
+    <span className="wrap-anywhere block whitespace-pre-line" data-slot="aui_user-inline-text">
       {nodes.map((node, nodeIndex) =>
         node.kind === 'inline-code' ? (
           <code
diff --git a/apps/desktop/src/styles.css b/apps/desktop/src/styles.css
index 2bd7556d848..76b31331680 100644
--- a/apps/desktop/src/styles.css
+++ b/apps/desktop/src/styles.css
@@ -823,6 +823,37 @@ canvas {
    content's --message-text-indent). No extra prose indent — a single gutter
    reads cleaner than a ragged tool-vs-reply column. */
 
+/* RTL/bidi chat text (#44150): each block resolves its own base direction from
+   its first strong char (UAX#9 plaintext). text-align:start makes that resolved
+   direction drive alignment too — load-bearing, since the user bubble pins
+   text-left. direction is never set, so chrome/layout/list-indent stay LTR (the
+   issue asks not to flip the whole UI). Covers assistant prose, user lines, and
+   both composers (main + edit share composer-rich-input). */
+[data-slot='aui_assistant-message-content'] .aui-md :where(p, h1, h2, h3, h4, h5, h6, li, blockquote),
+[data-slot='aui_user-inline-text'],
+[data-slot='composer-rich-input'] {
+  unicode-bidi: plaintext;
+  text-align: start;
+}
+
+/* Inline code/KaTeX don't vote on direction and keep their own order: isolate
+   makes bidi treat each as one neutral, so a block that *starts* with `./run.sh`
+   then Arabic still resolves RTL, and the command's neutrals (dots/slashes)
+   aren't reordered by the surrounding RTL run. */
+[data-slot='aui_assistant-message-content'] .aui-md :where(:not(pre) > code),
+[data-slot='aui_user-inline-code'],
+[data-slot='aui_assistant-message-content'] .aui-md .katex {
+  direction: ltr;
+  unicode-bidi: isolate;
+}
+
+/* Fenced code stays LTR even inside an RTL list item/blockquote — never mirrors. */
+[data-slot='aui_assistant-message-content'] .aui-md [data-slot='code-card'],
+[data-slot='aui_user-fence'] {
+  direction: ltr;
+  text-align: left;
+}
+
 [data-slot='aui_user-message-root'] {
   top: var(--sticky-human-top);
 }