From 7b4f6fc0d0c135c1f94524c0a007b77d757cc47a Mon Sep 17 00:00:00 2001
From: Talha Shafeeq <51529912+TalhaHunter101@users.noreply.github.com>
Date: Fri, 2 Oct 2026 03:55:18 +0500
Subject: [PATCH] fix(compat/truncate): escape string separator in RegExp
 (#2129)

---
 src/compat/string/truncate.spec.ts | 11 +++++++++++
 src/compat/string/truncate.ts      |  3 ++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/compat/string/truncate.spec.ts b/src/compat/string/truncate.spec.ts
index e64dafad3..621eb3b7e 100644
--- a/src/compat/string/truncate.spec.ts
+++ b/src/compat/string/truncate.spec.ts
@@ -121,4 +121,15 @@ describe('truncate', () => {
   it('should return base string with omission when separator is not found in truncated string', () => {
     expect(truncate('hello world test', { length: 10, separator: 'xyz' })).toEqual('hello w...');
   });
+
+  it('should support string separators containing RegExp special characters', () => {
+    expect(truncate('hello world? how are you doing?', { length: 20, separator: '?' })).toBe('hello world...');
+    expect(truncate('section [1] details and notes', { length: 20, separator: '[' })).toBe('section ...');
+    expect(truncate('part (A) overview notes', { length: 20, separator: '(' })).toBe('part ...');
+    expect(truncate('a + b + c + d + e', { length: 12, separator: '+' })).toBe('a + b ...');
+    expect(truncate('one*two*three*four', { length: 12, separator: '*' })).toBe('one*two...');
+    expect(truncate('hello.world.foo.bar', { length: 15, separator: '.' })).toBe('hello.world...');
+    expect(truncate('hello world foo bar', { length: 15, separator: '.' })).toBe('hello world ...');
+    expect(truncate('path\\to\\nested\\file', { length: 15, separator: '\\' })).toBe('path\\to...');
+  });
 });
diff --git a/src/compat/string/truncate.ts b/src/compat/string/truncate.ts
index 9ff6ac886..4fe57b977 100644
--- a/src/compat/string/truncate.ts
+++ b/src/compat/string/truncate.ts
@@ -1,3 +1,4 @@
+import { escapeRegExp } from '../../string/escapeRegExp.ts';
 import { regexMultiByte } from '../_internal/regexMultiByte.ts';
 import { isObject } from '../predicate/isObject.ts';
 
@@ -81,7 +82,7 @@ export function truncate(string?: string, options?: TruncateOptions): string {
   }
 
   // Further truncate the string to the last separator using unicode regex
-  const search = separator instanceof RegExp ? separator.source : separator;
+  const search = separator instanceof RegExp ? separator.source : escapeRegExp(separator);
   const flags = 'u' + (separator instanceof RegExp ? separator.flags.replace('u', '') : '');
   const withoutSeparator = new RegExp(`(?<result>.*(?:(?!${search}).))(?:${search})`, flags).exec(base);