fix: resolve math formula display abnormal after editing report

This fix addresses the issue where math formulas become corrupted or
incorrectly displayed after editing the generated report in the editor.

**Root Cause:**
The issue occurred due to incompatibility between markdown processing
in the display component and the Tiptap editor:
1. Display component used \[\] and \(\) LaTeX delimiters
2. Tiptap Mathematics extension expects $ and 70868 delimiters
3. tiptap-markdown didn't have built-in math node serialization
4. Math syntax was lost/corrupted during editor save operations

**Solution Implemented:**
1. Created MathematicsWithMarkdown extension that adds markdown
   serialization support to Tiptap's Mathematics nodes
2. Added math delimiter normalization functions:
   - normalizeMathForEditor(): Converts LaTeX delimiters to $/70868
   - normalizeMathForDisplay(): Standardizes all delimiters to 70868
3. Updated Markdown component to use new normalization
4. Updated ReportEditor to normalize content before loading

**Changes:**
- web/src/components/editor/math-serializer.ts (new)
- web/src/components/editor/extensions.tsx
- web/src/components/editor/index.tsx
- web/src/components/deer-flow/markdown.tsx
- web/src/core/utils/markdown.ts
- web/tests/markdown-math-editor.test.ts (new)
- web/tests/markdown-katex.test.ts

**Testing:**
- Added 15 comprehensive tests for math normalization round-trip
- All tests passing (math editor + existing katex tests)
- Verified TypeScript compilation and linting

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

web/src/components/deer-flow/markdown.tsx

@@ -14,7 +14,7 @@ import "katex/dist/katex.min.css";
 import { Button } from "~/components/ui/button";
 import { rehypeSplitWordsIntoSpans } from "~/core/rehype";
 import { katexOptions } from "~/core/markdown/katex";
-import { autoFixMarkdown } from "~/core/utils/markdown";
+import { autoFixMarkdown, normalizeMathForDisplay } from "~/core/utils/markdown";
 import { cn } from "~/lib/utils";
 
 import Image from "./image";
@@ -70,7 +70,7 @@ export function Markdown({
         {...props}
       >
         {autoFixMarkdown(
-          dropMarkdownQuote(processKatexInMarkdown(children ?? "")) ?? "",
+          dropMarkdownQuote(normalizeMathForDisplay(children ?? "")) ?? "",
         )}
       </ReactMarkdown>
       {enableCopy && typeof children === "string" && (
@@ -112,20 +112,7 @@ function CopyButton({ content }: { content: string }) {
   );
 }
 
-function processKatexInMarkdown(markdown?: string | null) {
-  if (!markdown) return markdown;
 
-  const markdownWithKatexSyntax = markdown
-    .replace(/\\\\\[/g, "$$$$") // Replace '\\[' with '$$'
-    .replace(/\\\\\]/g, "$$$$") // Replace '\\]' with '$$'
-    .replace(/\\\\\(/g, "$$$$") // Replace '\\(' with '$$'
-    .replace(/\\\\\)/g, "$$$$") // Replace '\\)' with '$$'
-    .replace(/\\\[/g, "$$$$") // Replace '\[' with '$$'
-    .replace(/\\\]/g, "$$$$") // Replace '\]' with '$$'
-    .replace(/\\\(/g, "$$$$") // Replace '\(' with '$$'
-    .replace(/\\\)/g, "$$$$"); // Replace '\)' with '$$';
-  return markdownWithKatexSyntax;
-}
 
 function dropMarkdownQuote(markdown?: string | null): string | null {
   if (!markdown) return null;

web/src/components/editor/extensions.tsx

@@ -10,7 +10,6 @@ import {
   GlobalDragHandle,
   HighlightExtension,
   HorizontalRule,
-  Mathematics,
   Placeholder,
   StarterKit,
   TaskItem,
@@ -31,6 +30,7 @@ import { TableRow } from "@tiptap/extension-table-row";
 import { TableCell } from "@tiptap/extension-table-cell";
 import { cx } from "class-variance-authority";
 import { common, createLowlight } from "lowlight";
+import { MathematicsWithMarkdown } from "./math-serializer";
 
 //TODO I am using cx here to get tailwind autocomplete working, idk if someone else can write a regex to just capture the class key in objects
 const aiHighlight = AIHighlight;
@@ -132,7 +132,7 @@ const twitter = Twitter.configure({
   inline: false,
 });
 
-const mathematics = Mathematics.configure({
+const mathematics = MathematicsWithMarkdown.configure({
   HTMLAttributes: {
     class: cx("text-foreground rounded p-1 hover:bg-accent cursor-pointer"),
   },

web/src/components/editor/index.tsx

@@ -31,6 +31,7 @@ import GenerativeMenuSwitch from "./generative/generative-menu-switch";
 import { uploadFn } from "./image-upload";
 import { TextButtons } from "./selectors/text-buttons";
 import { slashCommand, suggestionItems } from "./slash-command";
+import { normalizeMathForEditor } from "~/core/utils/markdown";
 // import { defaultEditorContent } from "./content";
 
 import "~/styles/prosemirror.css";
@@ -45,7 +46,13 @@ export interface ReportEditorProps {
 }
 
 const ReportEditor = ({ content, onMarkdownChange }: ReportEditorProps) => {
-  const [initialContent, setInitialContent] = useState<Content>(() => content);
+  const [initialContent, setInitialContent] = useState<Content>(() => {
+    // Normalize math delimiters for editor consumption
+    if (typeof content === "string") {
+      return normalizeMathForEditor(content);
+    }
+    return content;
+  });
   const [saveStatus, setSaveStatus] = useState("Saved");
 
   const [openNode, setOpenNode] = useState(false);

web/src/components/editor/math-serializer.ts

@@ -0,0 +1,34 @@
+// Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+// SPDX-License-Identifier: MIT
+
+import { Mathematics } from "novel";
+
+/**
+ * Extended Mathematics extension with markdown serialization support
+ * Handles both inline math ($...$) and block/display math ($$...$$)
+ */
+export const MathematicsWithMarkdown = Mathematics.extend({
+  addStorage() {
+    return {
+      markdown: {
+        serialize(state: any, node: any) {
+          const latex = node.attrs?.latex || "";
+          const isBlock = node.attrs?.display === true;
+          
+          if (isBlock) {
+            // Block/display math: $$...$$
+            state.write("$$");
+            state.write(latex);
+            state.write("$$");
+            state.closeBlock(node);
+          } else {
+            // Inline math: $...$
+            state.write("$");
+            state.write(latex);
+            state.write("$");
+          }
+        },
+      },
+    };
+  },
+});

web/src/core/utils/markdown.ts

@@ -2,6 +2,48 @@ export function autoFixMarkdown(markdown: string): string {
   return autoCloseTrailingLink(markdown);
 }
 
+/**
+ * Normalize math delimiters for editor consumption
+ * Converts display delimiters (\[...\], \\[...\\]) to $$ format
+ * Converts inline delimiters (\(...\), \\(...\\)) to $ format
+ * This ensures consistent format before loading into Tiptap editor
+ */
+export function normalizeMathForEditor(markdown: string): string {
+  let normalized = markdown;
+  
+  // Convert display math - handle double backslash first to avoid conflicts
+  normalized = normalized
+    .replace(/\\\\\[([^\]]*)\\\\\]/g, (_match, content) => `$$${content}$$`)  // \\[...\\] → $$...$$
+    .replace(/\\\[([^\]]*)\\\]/g, (_match, content) => `$$${content}$$`);  // \[...\] → $$...$$
+  
+  // Convert inline math - handle double backslash first to avoid conflicts
+  normalized = normalized
+    .replace(/\\\\\(([^)]*)\\\\\)/g, (_match, content) => `$${content}$`)  // \\(...\\) → $...$
+    .replace(/\\\(([^)]*)\\\)/g, (_match, content) => `$${content}$`);    // \(...\) → $...$
+  
+  return normalized;
+}
+
+/**
+ * Normalize math delimiters for display consumption
+ * Ensures all math delimiters are in $$ format for remarkMath/rehypeKatex
+ * This is used by the Markdown display component
+ */
+export function normalizeMathForDisplay(markdown: string): string {
+  let normalized = markdown;
+  
+  // Convert all LaTeX-style delimiters to $$
+  // Both display and inline math use $$ for display component (remarkMath handles both)
+  // Handle double backslash first to avoid conflicts
+  normalized = normalized
+    .replace(/\\\\\[([^\]]*)\\\\\]/g, (_match, content) => `$$${content}$$`)  // \\[...\\] → $$...$$
+    .replace(/\\\[([^\]]*)\\\]/g, (_match, content) => `$$${content}$$`)      // \[...\] → $$...$$
+    .replace(/\\\\\(([^)]*)\\\\\)/g, (_match, content) => `$$${content}$$`)   // \\(...\\) → $$...$$
+    .replace(/\\\(([^)]*)\\\)/g, (_match, content) => `$$${content}$$`);       // \(...\) → $$...$$
+  
+  return normalized;
+}
+
 function autoCloseTrailingLink(markdown: string): string {
   // Fix unclosed Markdown links or images
   let fixedMarkdown: string = markdown;