diff --git a/MastodonSDK/Sources/MastodonUI/Scene/ComposeContent/Helper/MastodonRegex.swift b/MastodonSDK/Sources/MastodonUI/Scene/ComposeContent/Helper/MastodonRegex.swift
index 76df541249..70dab7d5f1 100644
--- a/MastodonSDK/Sources/MastodonUI/Scene/ComposeContent/Helper/MastodonRegex.swift
+++ b/MastodonSDK/Sources/MastodonUI/Scene/ComposeContent/Helper/MastodonRegex.swift
@@ -11,7 +11,7 @@ public enum MastodonRegex {
     /// mention,  hashtag.
     /// @...
     /// #...
-    public static let highlightPattern = "(?:@([a-zA-Z0-9_]+)(@[a-zA-Z0-9_.-]+)?|#([^\\s.]+))"
+    public static let highlightPattern = "(?:@([\\p{L}\\p{M}\\p{N}_]+)(@[\\p{L}\\p{M}\\p{N}_.-]+)?|#([^\\s.]+))"
     /// emoji
     /// :shortcode:
     /// accept ^\B: or \s: but not accept \B: to force user input a space to make emoji take effect
@@ -21,7 +21,7 @@ public enum MastodonRegex {
     /// @…
     /// #…
     /// :…
-    public static let autoCompletePattern = "(?:@([a-zA-Z0-9_]+)(@[a-zA-Z0-9_.-]+)?|#([^\\s.]+))|(^\\B:|\\s:)([a-zA-Z0-9_]+)"
+    public static let autoCompletePattern = "(?:@([\\p{L}\\p{M}\\p{N}_]+)(@[\\p{L}\\p{M}\\p{N}_.-]+)?|#([^\\s.]+))|(^\\B:|\\s:)([a-zA-Z0-9_]+)"
 
     public enum Search {
         public static let username = "^@?[a-z0-9_-]+(@[\\S]+)?$"
diff --git a/MastodonTests/MastodonRegexTests.swift b/MastodonTests/MastodonRegexTests.swift
new file mode 100644
index 0000000000..cfceac4de0
--- /dev/null
+++ b/MastodonTests/MastodonRegexTests.swift
@@ -0,0 +1,180 @@
+//
+//  MastodonRegexTests.swift
+//  MastodonTests
+//
+//  Created by Assistant on 2025-11-02.
+//
+
+import XCTest
+@testable import Mastodon
+import MastodonUI
+
+final class MastodonRegexTests: XCTestCase {
+
+    func testExample() throws {
+        XCTAssertTrue(true)
+    }
+
+    func testUnicodeRegexPatterns() throws {
+        // Test that our regex patterns correctly match Unicode characters with combining marks
+        let highlightPattern = MastodonRegex.highlightPattern
+        let autoCompletePattern = MastodonRegex.autoCompletePattern
+
+        let testCases = [
+            "@café@examplë.com",
+            "@unikonstanz@bawü.social",
+            "@user@täst.de",
+            "@björn@exämple.com"
+        ]
+
+        // Test highlight pattern
+        let highlightRegex = try NSRegularExpression(pattern: highlightPattern, options: [])
+        for testCase in testCases {
+            let nsString = testCase as NSString
+            let range = NSRange(location: 0, length: nsString.length)
+            let matches = highlightRegex.matches(in: testCase, options: [], range: range)
+
+            XCTAssertEqual(matches.count, 1, "Highlight pattern should match \(testCase)")
+        }
+
+        // Test autocomplete pattern
+        let autoCompleteRegex = try NSRegularExpression(pattern: autoCompletePattern, options: [])
+        for testCase in testCases {
+            let nsString = testCase as NSString
+            let range = NSRange(location: 0, length: nsString.length)
+            let matches = autoCompleteRegex.matches(in: testCase, options: [], range: range)
+
+            XCTAssertEqual(matches.count, 1, "Autocomplete pattern should match \(testCase)")
+        }
+    }
+
+    func testHighlightPatternWithUnicodeCharacters() throws {
+        let highlightPattern = MastodonRegex.highlightPattern
+        let regex = try NSRegularExpression(pattern: highlightPattern, options: [])
+
+        // Test cases with unicode characters
+        let testCases = [
+            "@unikonstanz@bawü.social",
+            "@user@täst.de",
+            "@björn@exämple.com",
+            "@用户@example.com",
+            "@example@例え.テスト",
+            "@café@examplë.com"  // Test with combining marks
+        ]
+
+        for testCase in testCases {
+            let nsString = testCase as NSString
+            let range = NSRange(location: 0, length: nsString.length)
+            let matches = regex.matches(in: testCase, options: [], range: range)
+
+            // Should find exactly one match
+            XCTAssertEqual(matches.count, 1, "Failed to match \(testCase)")
+
+            if let match = matches.first {
+                // The full match should cover the entire string
+                XCTAssertEqual(match.range.location, 0)
+                XCTAssertEqual(match.range.length, nsString.length)
+
+                // The first capture group should be the username part
+                let usernameRange = match.range(at: 1)
+                if usernameRange.location != NSNotFound {
+                    let username = nsString.substring(with: usernameRange)
+                    XCTAssertTrue(username.count > 0, "Username capture group is empty for \(testCase)")
+                }
+
+                // The second capture group should be the domain part (if present)
+                let domainRange = match.range(at: 2)
+                if domainRange.location != NSNotFound {
+                    let domain = nsString.substring(with: domainRange)
+                    XCTAssertTrue(domain.count > 0, "Domain capture group is empty for \(testCase)")
+                }
+            }
+        }
+    }
+
+    func testAutoCompletePatternWithUnicodeCharacters() throws {
+        let autoCompletePattern = MastodonRegex.autoCompletePattern
+        let regex = try NSRegularExpression(pattern: autoCompletePattern, options: [])
+
+        // Test cases with unicode characters
+        let testCases = [
+            "@unikonstanz@bawü.social",
+            "@user@täst.de",
+            "@björn@exämple.com",
+            "@用户@example.com",
+            "@example@例え.テスト",
+            "@café@examplë.com"  // Test with combining marks
+        ]
+
+        for testCase in testCases {
+            let nsString = testCase as NSString
+            let range = NSRange(location: 0, length: nsString.length)
+            let matches = regex.matches(in: testCase, options: [], range: range)
+
+            // Should find exactly one match
+            XCTAssertEqual(matches.count, 1, "Failed to match \(testCase)")
+
+            if let match = matches.first {
+                // The full match should cover the entire string
+                XCTAssertEqual(match.range.location, 0)
+                XCTAssertEqual(match.range.length, nsString.length)
+            }
+        }
+    }
+
+    func testHighlightPatternWithAsciiCharacters() throws {
+        let highlightPattern = MastodonRegex.highlightPattern
+        let regex = try NSRegularExpression(pattern: highlightPattern, options: [])
+
+        // Test cases with ASCII characters (should still work)
+        let testCases = [
+            "@user@example.com",
+            "@test@domain.org",
+            "@simple@site.net",
+            "@café@example.com"  // Test with combining marks
+        ]
+
+        for testCase in testCases {
+            let nsString = testCase as NSString
+            let range = NSRange(location: 0, length: nsString.length)
+            let matches = regex.matches(in: testCase, options: [], range: range)
+
+            // Should find exactly one match
+            XCTAssertEqual(matches.count, 1, "Failed to match \(testCase)")
+
+            if let match = matches.first {
+                // The full match should cover the entire string
+                XCTAssertEqual(match.range.location, 0)
+                XCTAssertEqual(match.range.length, nsString.length)
+            }
+        }
+    }
+
+    func testAutoCompletePatternWithAsciiCharacters() throws {
+        let autoCompletePattern = MastodonRegex.autoCompletePattern
+        let regex = try NSRegularExpression(pattern: autoCompletePattern, options: [])
+
+        // Test cases with ASCII characters (should still work)
+        let testCases = [
+            "@user@example.com",
+            "@test@domain.org",
+            "@simple@site.net",
+            "@café@example.com"  // Test with combining marks
+        ]
+
+        for testCase in testCases {
+            let nsString = testCase as NSString
+            let range = NSRange(location: 0, length: nsString.length)
+            let matches = regex.matches(in: testCase, options: [], range: range)
+
+            // Should find exactly one match
+            XCTAssertEqual(matches.count, 1, "Failed to match \(testCase)")
+
+            if let match = matches.first {
+                // The full match should cover the entire string
+                XCTAssertEqual(match.range.location, 0)
+                XCTAssertEqual(match.range.length, nsString.length)
+            }
+        }
+    }
+}
\ No newline at end of file