From 618199701e61e9915ef80142f981056d14b9cc51 Mon Sep 17 00:00:00 2001
From: cycanic <79452786+cycanic@users.noreply.github.com>
Date: Sat, 14 Nov 2026 16:50:24 +0400
Subject: [PATCH] fix: keep the curly apostrophe when folding a lookalike word
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The fold ran every character of an affected token through the confusables
map, including U+2019, whose prototype is ASCII "'". So "Ivа’s" (Cyrillic
а) normalized to "Iva's" instead of "Iva’s". The apostrophe is punctuation
the token admits, not a lookalike; leave it as typed. Detection is
unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 .changeset/keep-curly-apostrophe.md | 11 +++++++++++
 src/analyze.ts                      |  3 +++
 test/analyze.test.ts                |  8 ++++++++
 test/cases.data.ts                  |  7 +++++++
 4 files changed, 29 insertions(+)
 create mode 100644 .changeset/keep-curly-apostrophe.md

diff --git a/.changeset/keep-curly-apostrophe.md b/.changeset/keep-curly-apostrophe.md
new file mode 100644
index 0000000..5b97fd5
--- /dev/null
+++ b/.changeset/keep-curly-apostrophe.md
@@ -0,0 +1,11 @@
+---
+'@moderation-api/unicode-spoofing': patch
+---
+
+Keep the typographic apostrophe in `normalized` when a lookalike word is folded.
+
+`Ivа’s` (with a Cyrillic `а`) normalized to `Iva's`: the fold ran every
+character of the word through the confusables map, including U+2019, whose
+prototype is the ASCII `'`. Only the letters are lookalikes, so the apostrophe
+is now kept as typed and the word normalizes to `Iva’s`. Detection is
+unchanged.
diff --git a/src/analyze.ts b/src/analyze.ts
index cccee8e..3b2a83a 100644
--- a/src/analyze.ts
+++ b/src/analyze.ts
@@ -425,6 +425,9 @@ function analyzeToken(
           return '';
         if (zalgo && MARK_RE.test(ch)) return '';
         if (nfkcFold) return ch;
+        // The apostrophe is punctuation the token admits, not a lookalike:
+        // folding it would turn "Ivа’s" into "Iva's" rather than "Iva’s".
+        if (ch === '’') return ch;
         return foldLookalikes ? foldChar(ch) : ch;
       })
       .join('');
diff --git a/test/analyze.test.ts b/test/analyze.test.ts
index 4ad838f..62b8fb2 100644
--- a/test/analyze.test.ts
+++ b/test/analyze.test.ts
@@ -133,6 +133,14 @@ describe('analyze — legitimate content', () => {
     expect(r.signals.mixed_script).toBe(true);
   });
 
+  it('keeps the curly apostrophe when it folds a lookalike word', () => {
+    // Only the letters are lookalikes; the apostrophe is the author's own
+    // punctuation and survives normalization as typed.
+    expect(analyze('Ivа’s').normalized).toBe('Iva’s');
+    expect(analyze("Ivа's").normalized).toBe("Iva's");
+    expect(analyze('the boss’ НОТ’ deal').normalized).toBe('the boss’ HOT’ deal');
+  });
+
   // A word already written in Latin cannot be impersonating Latin, so the only
   // thing the skeleton test measures there is whether the fold happens to reach
   // ASCII — which it does for ordinary European letters, and arbitrarily: "æ"
diff --git a/test/cases.data.ts b/test/cases.data.ts
index 7e1b50e..cfd1473 100644
--- a/test/cases.data.ts
+++ b/test/cases.data.ts
@@ -64,6 +64,13 @@ export interface SpoofCase {
 }
 
 export const CASES: SpoofCase[] = [
+  {
+    category: 'confusable',
+    name: 'keeps the curly apostrophe of a folded word (Ivа’s → Iva’s)',
+    input: 'Ivа’s',
+    status: 'supported',
+    expect: { spoofed: true, signals: { mixed_script: true }, normalized: 'Iva’s' },
+  },
   {
     category: 'confusable',
     name: 'flags a Cyrillic whole-word lookalike and normalizes it (НОТ → HOT)',