fix(models): probe /v1/models for path-less LM Studio endpoints

Probe /v1/models for path-less OpenAI-compatible model endpoints and surface clearer LM Studio diagnostics with the actual probed URL.

routes/model_routes.py

@@ -870,15 +870,52 @@ def _ping_endpoint(base_url: str, api_key: str = None, timeout: float = 1.5) ->
 
 
 def _model_endpoint_error_message(base_url: str, ping: Dict[str, Any] = None) -> str:
-    """Return a provider-aware error message for failed endpoint probes."""
+    """Return a provider-aware error message for failed endpoint probes.
+
+    Surfaces the URL we actually probed and, when the endpoint looks like
+    LM Studio (port 1234 or hostname match), adds a hint about loading a
+    model and confirming the Developer Server is running. The user previously
+    saw a generic "No models found for that provider/key" with no way to
+    tell whether the URL was wrong, the server was down, or the server was
+    reachable but had no model loaded (issue #25).
+    """
     ping = ping or {}
     error = ping.get("error")
+    from src.endpoint_resolver import build_models_url
+    try:
+        probed = build_models_url(base_url) or base_url
+    except Exception:
+        probed = base_url
     parsed = urlparse(base_url)
     host = (parsed.hostname or "").lower()
     is_ollama = parsed.port == 11434 or "ollama" in host or "ollama" in base_url.lower()
+    is_lmstudio = (
+        parsed.port == 1234
+        or "lmstudio" in host
+        or "lm-studio" in host
+        or "lm_studio" in host
+    )
+
+    if is_lmstudio:
+        parts = [
+            "LM Studio is reachable, but no models were reported.",
+            f"Probed {probed}.",
+        ]
+        if error:
+            parts.append(f"Last probe error: {error}.")
+        parts.append(
+            "Open LM Studio, load at least one model, and confirm the "
+            "Developer Server is running on port 1234."
+        )
+        parts.append(
+            "Base URL should be http://localhost:1234/v1 (native) or "
+            "http://host.docker.internal:1234/v1 (Docker)."
+        )
+        return " ".join(parts)
 
     if is_ollama:
         parts = ["No Ollama models found for that endpoint."]
+        parts.append(f"Probed {probed}.")
         if error:
             parts.append(f"Last probe error: {error}.")
         parts.append("Check that Ollama is running and that the base URL is correct.")
@@ -888,9 +925,9 @@ def _model_endpoint_error_message(base_url: str, ping: Dict[str, Any] = None) ->
         return " ".join(parts)
 
     if error:
-        return f"No models found for that provider/key. Last probe error: {error}."
+        return f"No models found for that provider/key. Probed {probed}. Last probe error: {error}."
 
-    return "No models found for that provider/key."
+    return f"No models found for that provider/key. Probed {probed}."
 
 
 def _normalize_model_ids(value):