fix: detect Claude Code 2.1+ session title requests for optimization skip

Expand is_title_generation_request to match sentence-case/JSON title prompts
in addition to legacy new-conversation-topic copy. Add unit test for the
current session-title system text shape.

api/detection.py

@@ -31,11 +31,24 @@ def is_title_generation_request(request_data: MessagesRequest) -> bool:
 
     Title generation requests are detected by a system prompt containing
     title extraction instructions, no tools, and a single user message.
+
+    Matches both legacy phrasing and Claude Code 2.1+ session title prompts
+    (JSON \"title\" field, sentence-case title instructions, etc.).
     """
     if not request_data.system or request_data.tools:
         return False
     system_text = extract_text_from_content(request_data.system).lower()
-    return "new conversation topic" in system_text and "title" in system_text
+    if "title" not in system_text:
+        return False
+    return (
+        "new conversation topic" in system_text
+        or "sentence-case title" in system_text
+        or (
+            "return json" in system_text
+            and "field" in system_text
+            and ("coding session" in system_text or "this session" in system_text)
+        )
+    )
 
 
 def is_prefix_detection_request(request_data: MessagesRequest) -> tuple[bool, str]:

tests/api/test_request_utils.py

@@ -151,6 +151,20 @@ class TestTitleGenerationRequest:
 
         assert is_title_generation_request(req) is False
 
+    def test_title_generation_claude_code_session_title_prompt(self):
+        """Claude Code 2.1+ session title JSON (sentence-case) is detected."""
+        block = MagicMock()
+        block.text = (
+            "Generate a concise, sentence-case title (3-7 words) that captures the "
+            "main topic or goal of this coding session. Return JSON with a single "
+            '"title" field.'
+        )
+        req = MagicMock(spec=MessagesRequest)
+        req.system = [block]
+        req.tools = None
+
+        assert is_title_generation_request(req) is True
+
 
 class TestExtractCommandPrefix:
     """Tests for extract_command_prefix function."""