Fix missing extracted classes in mdx files (#19711)

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Allow trailing dash in functional utility names for backwards compatibility ([#19696](https://github.com/tailwindlabs/tailwindcss/pull/19696))
+- Fix missing extracted classes in mdx files containing `.` ([#19711](https://github.com/tailwindlabs/tailwindcss/pull/19711))
 
 ## [4.2.0] - 2026-02-18
 

crates/oxide/src/extractor/pre_processors/markdown.rs

@@ -9,6 +9,7 @@ impl PreProcessor for Markdown {
         let len = content.len();
         let mut result = content.to_vec();
         let mut cursor = cursor::Cursor::new(content);
+        let mut bracket_stack = vec![];
 
         let mut in_directive = false;
 
@@ -18,11 +19,17 @@ impl PreProcessor for Markdown {
                     result[cursor.pos] = b' ';
                     in_directive = true;
                 }
+                (true, b'(' | b'[' | b'{' | b'<') => {
+                    bracket_stack.push(cursor.curr());
+                }
+                (true, b')' | b']' | b'}' | b'>') if !bracket_stack.is_empty() => {
+                    bracket_stack.pop();
+                }
                 (true, b'}') => {
                     result[cursor.pos] = b' ';
                     in_directive = false;
                 }
-                (true, b'.') => {
+                (true, b'.') if bracket_stack.is_empty() => {
                     result[cursor.pos] = b' ';
                 }
                 _ => {}
@@ -60,4 +67,17 @@ mod tests {
             Markdown::test(input, expected);
         }
     }
+
+    #[test]
+    fn test_nested_classes_keep_the_dots() {
+        for (input, expected) in [
+            (
+                r#"{<div class="px-2.5"></div>}"#,
+                r#" <div class="px-2.5"></div> "#,
+            ),
+            (r#"{content-['example.js']}"#, r#" content-['example.js'] "#),
+        ] {
+            Markdown::test(input, expected);
+        }
+    }
 }