A title call that could not survive a model that thinks

Reported: chat names never regenerate after the first reply. They were
regenerating; the request was being made and the answer thrown away.

`complete()` returns `message.content` verbatim, and a model that emits
`<think>` inline puts its thinking in exactly the field the title is read from.
So the title came back as "<think>Okay, the user wants a short title for" --
or, once the too-long guard caught that, as the first prompt trimmed, which is
indistinguishable from titling never having run. That is what was being seen.

Underneath it, `max_tokens: 24`. Ample for six words, and nowhere near enough
for a model that reasons first: the budget goes on thinking and the content
field comes back empty or holding an unclosed tag. Too small is not a shorter
title, it is no title at all.

Both fixed: the reply goes through `reasoning.strip_reasoning`, and the budget
is `TITLE_MAX_TOKENS` with room to think. Reproduced first against the four
shapes an endpoint actually answers with -- three of them were broken -- and
the tests are written from those.

What I did *not* do is ask for a low reasoning effort on the call, which would
make it much cheaper and was the obvious move. `reasoning_effort` and
`chat_template_kwargs` appear only where somebody has opted in, so that a
provider strict about unknown parameters sees exactly the request it always
did. An LLMError here is caught and turned into a fallback title -- so a 400
would be titling silently switching itself off, which is the failure this
commit exists to fix. The token budget makes the room instead.

The shipped prompt now asks for a leading emoji, as requested. Asked for rather
than assumed: a model that ignores it gives a title without one, and an
administrator who does not want them clears the word.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/test_chat.py

@@ -156,6 +156,106 @@ async def test_the_title_prompt_carries_the_exchange(mock_http):
     assert seen == ["Name this: What is lembas? / Waybread. / {{nonsense}}"]
 
 
+async def test_a_title_from_a_model_that_thinks_first(mock_http):
+    """The bug: a reasoning model puts `<think>` in the very field the title is
+    read from, so every chat on one was named "<think>Okay, the user wants a
+    short title for" -- or, once the guard caught that as too long, fell back to
+    the first prompt and looked as though titling had never run at all."""
+
+    def handler(_request: httpx.Request) -> httpx.Response:
+        return httpx.Response(
+            200,
+            json={
+                "choices": [
+                    {
+                        "message": {
+                            "content": "<think>Six words, an emoji</think>\n"
+                            "🌳 Mallorn trees explained"
+                        }
+                    }
+                ]
+            },
+        )
+
+    mock_http(handler)
+    title = await chat_service.generate_title(
+        Endpoint("http://x.test", "", {}),
+        "m",
+        "What is a mallorn?",
+        "A golden tree.",
+        template="Name this: {{question}}",
+    )
+    assert title == "🌳 Mallorn trees explained"
+
+
+async def test_the_title_call_leaves_room_to_think(mock_http):
+    """24 tokens is ample for six words and nowhere near enough for a model that
+    reasons first: the budget went on thinking and the content came back empty.
+    Too small is not a shorter title, it is no title."""
+    seen: list[dict] = []
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        seen.append(json.loads(request.content))
+        return httpx.Response(200, json={"choices": [{"message": {"content": "A name"}}]})
+
+    mock_http(handler)
+    await chat_service.generate_title(
+        Endpoint("http://x.test", "", {}), "m", "q", "a", template="Name this: {{question}}"
+    )
+    assert seen[0]["max_tokens"] == chat_service.TITLE_MAX_TOKENS
+    assert seen[0]["max_tokens"] >= 256
+
+
+async def test_the_title_call_sends_no_reasoning_effort(mock_http):
+    """Tempting, and wrong. Those two fields appear only when somebody has opted
+    in, so a provider strict about unknown parameters sees the request it always
+    did -- and a 400 here is caught and turned into a fallback title, which is
+    titling silently switching itself off."""
+    seen: list[dict] = []
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        seen.append(json.loads(request.content))
+        return httpx.Response(200, json={"choices": [{"message": {"content": "A name"}}]})
+
+    mock_http(handler)
+    await chat_service.generate_title(
+        Endpoint("http://x.test", "", {}), "m", "q", "a", template="Name this: {{question}}"
+    )
+    assert "reasoning_effort" not in seen[0]
+    assert "chat_template_kwargs" not in seen[0]
+
+
+async def test_a_title_that_is_only_thinking_falls_back(mock_http):
+    """Nothing but reasoning means nothing to name it with. The first prompt is
+    a better title than an empty one."""
+
+    def handler(_request: httpx.Request) -> httpx.Response:
+        return httpx.Response(
+            200, json={"choices": [{"message": {"content": "<think>still deciding"}}]}
+        )
+
+    mock_http(handler)
+    title = await chat_service.generate_title(
+        Endpoint("http://x.test", "", {}),
+        "m",
+        "What is a mallorn?",
+        "A golden tree.",
+        template="Name this: {{question}}",
+    )
+    assert title == "What is a mallorn?"
+
+
+def test_the_shipped_title_prompt_asks_for_an_emoji():
+    """It makes a sidebar of twenty chats scannable, and it is asked for rather
+    than assumed -- a model that ignores it gives a title without one."""
+    from lembas.services import prompts
+
+    fragment = next(f for f in prompts.BUILTIN if f.key == "task.title")
+    assert "emoji" in fragment.default
+    assert "{{question}}" in fragment.default
+    assert "{{answer}}" in fragment.default
+
+
 async def test_an_empty_title_prompt_asks_no_model_at_all(mock_http):
     """Clearing the fragment is how auto-titling is turned off. It must not
     cost a request that is then thrown away."""