@@ -56,7 +56,9 @@ int _cellCount(String row) {
 }
 
 final _fenceMarker = RegExp(r'^(`{3,}|~{3,})');
+// Each blank run has one place to go, so a long run followed by a stray
+// character fails in linear time instead of retrying every split.
 final _delimiterRow = RegExp(
-  r'^ {0,3}\|?\s*:?-+:?\s*(?:\|\s*:?-+:?\s*)*\|?\s*$',
+  r'^ {0,3}\|?\s*:?-+:?\s*(?:\|\s*:?-+:?\s*)*(?:\|\s*)?$',
 );
 final _unescapedPipe = RegExp(r'(?<!\\)\|');
@@ -0,0 +1,19 @@
+import 'package:buzz/features/channels/message_content/markdown_tables.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  test('separates a table from its caption', () {
+    expect(
+      separateMarkdownTables('Results:\n| a | b |\n|---|:-:|\n| 1 | 2 |'),
+      'Results:\n\n| a | b |\n|---|:-:|\n| 1 | 2 |',
+    );
+  });
+
+  test('a long blank run in a delimiter row takes linear time', () {
+    // Overlapping blank runs retried every split: about a second at 20,000.
+    final content = 'caption\n| a |\n|---${' ' * 200000}x|';
+    final timer = Stopwatch()..start();
+    expect(separateMarkdownTables(content), content);
+    expect(timer.elapsedMilliseconds, lessThan(500));
+  });
+}