From f4e967bf220d6deba7cf63028def8b2f00bcc030 Mon Sep 17 00:00:00 2001
From: Marco Beretta <81851188+berry-13@users.noreply.github.com>
Date: Sat, 5 Sep 2026 14:16:17 +0200
Subject: [PATCH] =?UTF-8?q?=F0=9F=A9=B9=20fix:=20Restore=20the=20Client=20?=
 =?UTF-8?q?Build=20by=20Parsing=20Single-Dollar=20Math=20via=20Micromark?=
 =?UTF-8?q?=20(#15638)?=
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`markdownToHtml` (#15087) imported `preprocessLaTeX` from `client/src/utils/latex.ts`,
but #15181 replaced that preprocessing pass with the currency-safe `singleDollarMath`
micromark construct and removed the function. The symbol exists nowhere in the repo, so
`dev` fails `tsc --noEmit` with TS2305 and the Vite build with
`[MISSING_EXPORT] "preprocessLaTeX" is not exported by "src/utils/latex.ts"`, which reds
out the client typecheck, the build verification, and every job downstream of the client
build on `dev` and on every open pull request.

Register `singleDollarMath` in the extension list when `mode.latex` is set instead. That
is exactly what the message renderers do — `markdownConfig.ts` adds `remarkSingleDollarMath`
only when `latexParsing` is on, and that plugin does nothing but push `singleDollarMath`
into `micromarkExtensions` — so clipboard HTML keeps mirroring the rendered message, which
is the parity this helper is built around. `markdownToHtml` parses with `fromMarkdown`
directly rather than through unified, so the extension array is the equivalent seam.

Both specs already pinned the intended behavior and pass unchanged: `$E=mc^2$` becomes
inline math under `latex: true`, `$5 to $10` stays currency. Their titles said
"preprocesses", which no longer names a mechanism that exists; they now say "parses".
---
 client/src/utils/richtext.spec.ts |  4 ++--
 client/src/utils/richtext.ts      | 18 ++++++++++--------
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/client/src/utils/richtext.spec.ts b/client/src/utils/richtext.spec.ts
index 7ca85bc184..4752094b1c 100644
--- a/client/src/utils/richtext.spec.ts
+++ b/client/src/utils/richtext.spec.ts
@@ -113,14 +113,14 @@ describe('markdownToHtml', () => {
     );
   });
 
-  it('renders single-dollar math when the renderer preprocesses LaTeX', () => {
+  it('renders single-dollar math when the renderer parses LaTeX', () => {
     expect(markdownToHtml('Energy is $E=mc^2$ inline.', { variant: 'full', latex: true })).toBe(
       '<p>Energy is E=mc^2 inline.</p>',
     );
     expect(markdownToHtml('Energy is $E=mc^2$ inline.')).toBe('<p>Energy is $E=mc^2$ inline.</p>');
   });
 
-  it('still leaves currency alone with LaTeX preprocessing on', () => {
+  it('still leaves currency alone with LaTeX parsing on', () => {
     expect(markdownToHtml('Costs rose from $5 to $10.', { variant: 'full', latex: true })).toBe(
       '<p>Costs rose from $5 to $10.</p>',
     );
diff --git a/client/src/utils/richtext.ts b/client/src/utils/richtext.ts
index e54269740b..b4304cbd6e 100644
--- a/client/src/utils/richtext.ts
+++ b/client/src/utils/richtext.ts
@@ -20,7 +20,7 @@ import type {
 import type { Extension as MicromarkExtension } from 'micromark-util-types';
 import { mcpUIResourcePlugin } from '~/components/MCPUIResource/plugin';
 import { remarkApproxTilde } from './tilde';
-import { preprocessLaTeX } from './latex';
+import { singleDollarMath } from './latex';
 
 /**
  * Which message renderer this copy has to match. `Markdown` (assistant turns)
@@ -404,10 +404,11 @@ function serializeChildren(nodes: readonly SerializableNode[], context: Serializ
  * the clipboard as `text/html`. Paste targets that ignore Markdown (Teams,
  * Outlook, Word) strip stylesheets, so every visual cue has to be inline.
  *
- * Parsing mirrors the message renderers: the same LaTeX preprocessing, the same
- * micromark extensions with `singleDollarTextMath` off so currency such as
- * `$5 to $10` stays currency, then the same `remarkApproxTilde` and
- * `remark-supersub` transforms they apply to the parsed tree.
+ * Parsing mirrors the message renderers: the same currency-safe single-dollar
+ * math extension, the same `micromark-extension-math` with `singleDollarTextMath`
+ * off so currency such as `$5 to $10` stays currency, then the same
+ * `remarkApproxTilde` and `remark-supersub` transforms they apply to the parsed
+ * tree.
  */
 export function markdownToHtml(
   markdown: string,
@@ -417,10 +418,11 @@ export function markdownToHtml(
   if (mode.variant === 'full') {
     extensions.push(directive());
   }
+  if (mode.latex) {
+    extensions.push(singleDollarMath);
+  }
 
-  const source = mode.latex ? preprocessLaTeX(markdown) : markdown;
-
-  const tree = fromMarkdown(source, {
+  const tree = fromMarkdown(markdown, {
     extensions,
     mdastExtensions: [gfmFromMarkdown(), directiveFromMarkdown(), mathFromMarkdown()],
   });