Prevent inline math input rule from replacing previous character

.changeset/yellow-bags-pump.md

@@ -0,0 +1,7 @@
+---
+'@tiptap/extension-mathematics': minor
+---
+
+Prevent inline math input rule from replacing previous character
+
+- Changed input rule to utilize negative lookbehind rather than regular character match to ensure preceding character is not consumed in final match. This ensures the range's `from` position is correctly at the start o the double `$` signs.

packages/extension-mathematics/src/extensions/InlineMath.ts

@@ -220,7 +220,7 @@ export const InlineMath = Node.create<InlineMathOptions>({
   addInputRules() {
     return [
       new InputRule({
-        find: /(^|[^$])(\$\$([^$\n]+?)\$\$)(?!\$)/,
+        find: /(?<!$)(\$\$([^$\n]+?)\$\$)(?!\$)/,
         handler: ({ state, range, match }) => {
           const latex = match[3]
           const { tr } = state