diff --git a/commit_check/ai_signatures_data.py b/commit_check/ai_signatures_data.py
index 2924eea9..d247a405 100644
--- a/commit_check/ai_signatures_data.py
+++ b/commit_check/ai_signatures_data.py
@@ -89,6 +89,14 @@ def _body_marker(pattern: str, description: str = "") -> AiSignaturePattern:
             r"|\d+\+Claude@users\.noreply\.github\.com)>)?",
             "``Co-authored-by: Claude`` trailer",
         ),
+        # Any co-author name with the Anthropic noreply email — catches
+        # model-name variants such as "Claude Opus 4.5 (1M context)" that
+        # the pattern above misses.
+        _trailer(
+            "Co-authored-by",
+            r"[^<\n]*<noreply@anthropic\.com>",
+            "``Co-authored-by`` with Anthropic noreply email",
+        ),
         # Assisted-by trailer (Linux kernel style, with optional tool list)
         _trailer(
             "Assisted-by",
@@ -223,6 +231,16 @@ def _body_marker(pattern: str, description: str = "") -> AiSignaturePattern:
             r"(?:claude|gpt|gemini)[\w.]*-[\w.-]+(?:\s*<[^>]*>)?",
             "``Co-authored-by`` with AI model name",
         ),
+        # Catch space-separated AI model identifiers in Co-authored-by
+        # (e.g. "Claude Opus 4.5", "Gemini 2.5 Pro", "GPT 4 Turbo").
+        # A purely numeric version token is required so human names with
+        # ordinals ("Claude Dubois 3rd") are NOT flagged.
+        _trailer(
+            "Co-authored-by",
+            r"(?:claude|gpt|gemini)(?:\s+[a-z]+)*\s+\d+(?:\.\d+)*(?!\w)"
+            r"(?:\s+[a-z]+)*(?:\s*\([^)]*\))?(?:\s*<[^>]*>)?",
+            "``Co-authored-by`` with space-separated AI model name",
+        ),
         # Catch Assisted-by trailer (Linux kernel style) regardless of agent,
         # with optional trailing tool list.
         _trailer(
diff --git a/tests/ai_signatures_test.py b/tests/ai_signatures_test.py
index 4a755e25..ba3b1931 100644
--- a/tests/ai_signatures_test.py
+++ b/tests/ai_signatures_test.py
@@ -47,6 +47,35 @@ def test_human_claude_with_personal_email_ignored(self):
         claude_hits = [s for s in result if s["tool"] == "Claude Code"]
         assert len(claude_hits) == 0
 
+    @pytest.mark.benchmark
+    def test_claude_model_name_with_noreply_email(self):
+        """Model-name co-author with anthropic noreply is detected."""
+        message = (
+            "feat: add feature\n\n"
+            "Co-authored-by: Claude Opus 4.5 (1M context) <noreply@anthropic.com>"
+        )
+        result = detect_ai_signatures(message)
+        assert any(s["tool"] == "Claude Code" for s in result)
+
+    @pytest.mark.benchmark
+    def test_space_separated_model_name_detected(self):
+        """Space-separated model names with a version are detected."""
+        for trailer in (
+            "Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>",
+            "Co-authored-by: Gemini 2.5 Pro <gemini@example.com>",
+            "Co-authored-by: GPT 4 Turbo",
+        ):
+            message = f"feat: add feature\n\n{trailer}"
+            assert has_ai_signature(message), trailer
+
+    @pytest.mark.benchmark
+    def test_human_name_with_ordinal_ignored(self):
+        """A human name with an ordinal suffix is NOT detected."""
+        message = (
+            "feat: add feature\n\nCo-authored-by: Claude Dubois 3rd <claude@gmail.com>"
+        )
+        assert not has_ai_signature(message)
+
     @pytest.mark.benchmark
     def test_copilot_with_noreply_email(self):
         """Co-authored-by: Copilot with GitHub noreply is detected."""