diff --git a/ai-hub/app/api/schemas.py b/ai-hub/app/api/schemas.py
index 3719e34..58b1412 100644
--- a/ai-hub/app/api/schemas.py
+++ b/ai-hub/app/api/schemas.py
@@ -79,7 +79,7 @@
     """Defines the shape of a request to the /chat endpoint."""
     prompt: str = Field(..., min_length=1)
     # The 'model' can now be specified in the request body to switch models mid-conversation.
-    provider_name: Literal["deepseek", "gemini"] = Field("deepseek")
+    provider_name: str = Field("gemini")
     # Add a new optional boolean field to control the retriever
     load_faiss_retriever: Optional[bool] = Field(False, description="Whether to use the FAISS DB retriever for the chat.")
 
diff --git a/ui/client-app/src/services/apiService.js b/ui/client-app/src/services/apiService.js
index 8313fb6..8524cb5 100644
--- a/ui/client-app/src/services/apiService.js
+++ b/ui/client-app/src/services/apiService.js
@@ -311,7 +311,19 @@
     body: JSON.stringify({ prompt: prompt, provider_name: providerName }),
   });
   if (!response.ok) {
-    throw new Error("LLM API failed");
+    let detail = "LLM API failed";
+    try {
+      const errBody = await response.json();
+      if (typeof errBody.detail === "string") {
+        detail = errBody.detail;
+      } else if (Array.isArray(errBody.detail)) {
+        // Pydantic 422 errors: [{"loc":..., "msg":..., "type":...}]
+        detail = errBody.detail.map((err) => `${err.loc.join(".")}: ${err.msg}`).join("; ");
+      } else if (errBody.detail) {
+        detail = JSON.stringify(errBody.detail);
+      }
+    } catch { }
+    throw new Error(detail);
   }
   const result = await response.json();
   return result;