Reading the answer instead of asking somebody to know it

llama-server publishes the loaded model's Jinja chat template on /props, and
that template is the very thing that rejects a reasoning effort it does not
recognise -- so the accepted set is written down, authoritatively, in a place
this application can simply read. There is a button on the model's page that
does.

The parser handles both shapes a template uses: the values inline in the test
that rejects them (Bonsai), and a named list set elsewhere with nothing near
the mention spelling them out (gpt-oss). It is deliberately conservative,
because a wrong answer here silently removes a level somebody is entitled to:
only known efforts count, an unrelated list of quoted strings is ignored, and a
single match is read as a default -- `{%- set reasoning_effort = 'medium' %}`
-- rather than as a vocabulary of one.

An endpoint with no such route says so. OpenAI and vLLM do not publish a
template, and "this cannot tell us" must not be recorded as "this model accepts
nothing".

/props sits at the server root, beside the OpenAI-compatible surface rather
than inside it, so a base URL written as .../v1 needs the suffix stripped.
Getting that wrong is a silent 404 that looks like detection simply not
working, so there is a test on it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/lembas/services/llm/openai_client.py

@@ -68,6 +68,19 @@ class Endpoint:
             base = f"{base}/v1"
         return f"{base}/{path.lstrip('/')}"
 
+    def root_url(self, path: str) -> str:
+        """A URL at the *server's* root rather than under `/v1`.
+
+        llama-server's own endpoints -- `/props` is the one that matters here --
+        sit beside the OpenAI-compatible surface, not inside it. A base URL may
+        be written either way (`http://host:8080` or `.../v1`), so the suffix is
+        stripped rather than assumed absent.
+        """
+        base = self.base_url.rstrip("/")
+        if base.endswith("/v1"):
+            base = base[: -len("/v1")]
+        return f"{base}/{path.lstrip('/')}"
+
     def headers(self) -> dict[str, str]:
         headers = {"Content-Type": "application/json", **self.extra_headers}
         # Local endpoints frequently need no key at all; sending an empty
@@ -77,6 +90,30 @@ class Endpoint:
         return headers
 
 
+async def fetch_chat_template(endpoint: Endpoint) -> str:
+    """The model's own Jinja chat template, from llama-server's `/props`.
+
+    The one place the truth about a model's accepted values is actually
+    written down: `/props` returns `chat_template` verbatim, and that template
+    is what raises when it meets a `reasoning_effort` it does not know.
+
+    Returns "" rather than raising for anything that is not a llama-server --
+    OpenAI, vLLM and the rest have no such route, and "this endpoint cannot
+    tell us" is a normal answer here, not a failure.
+    """
+    try:
+        async with httpx.AsyncClient(timeout=10.0) as client:
+            response = await client.get(
+                endpoint.root_url("props"), headers=endpoint.headers()
+            )
+            response.raise_for_status()
+            payload = response.json()
+    except (httpx.HTTPError, ValueError, json.JSONDecodeError):
+        return ""
+    template = payload.get("chat_template") if isinstance(payload, dict) else ""
+    return template if isinstance(template, str) else ""
+
+
 def describe_http_error(exc: httpx.HTTPStatusError) -> str:
     """Turn an upstream error response into something worth reading.