Add clear error messages for LLM initialization failures

src/webui/components/browser_use_agent_tab.py

@@ -430,6 +430,44 @@ async def run_agent_task(
         llm_api_key,
         ollama_num_ctx if llm_provider_name == "ollama" else None,
     )
+    
+    # Check if LLM was initialized successfully
+    if not main_llm:
+        error_msg = "❌ **LLM Initialization Failed**\n\n"
+        if not llm_provider_name or not llm_model_name:
+            error_msg += "**Issue:** No LLM provider or model selected.\n\n"
+            error_msg += "**Solution:**\n"
+            error_msg += "1. Go to **⚙️ AGENT CONFIG** tab\n"
+            error_msg += "2. Select **LLM Provider** (e.g., Google - Gemini)\n"
+            error_msg += "3. Enter your **API Key**\n"
+            error_msg += "4. Select a **Model** (e.g., gemini-2.0-flash-exp)\n"
+            error_msg += "5. Come back and try again!\n"
+        elif not llm_api_key:
+            error_msg += "**Issue:** API Key is missing.\n\n"
+            error_msg += "**Solution:**\n"
+            error_msg += "1. Go to **⚙️ AGENT CONFIG** tab\n"
+            error_msg += "2. Enter your **LLM API Key**\n"
+            error_msg += "3. Make sure it's valid and has credits\n"
+            error_msg += "4. Come back and try again!\n"
+        else:
+            error_msg += "**Issue:** Failed to initialize the LLM.\n\n"
+            error_msg += "**Possible causes:**\n"
+            error_msg += "- Invalid API key\n"
+            error_msg += "- API key has no credits\n"
+            error_msg += "- Network connection issue\n"
+            error_msg += "- Model name is incorrect\n\n"
+            error_msg += "**Solution:** Check your settings in **⚙️ AGENT CONFIG** tab\n"
+        
+        webui_manager.bu_chat_history.append({"role": "assistant", "content": error_msg})
+        yield {
+            user_input_comp: gr.update(interactive=True, placeholder="Fix LLM settings and try again..."),
+            run_button_comp: gr.update(value="▶️ Submit Task", interactive=True),
+            stop_button_comp: gr.update(interactive=False),
+            pause_resume_button_comp: gr.update(interactive=False),
+            clear_button_comp: gr.update(interactive=True),
+            chatbot_comp: gr.update(value=webui_manager.bu_chat_history),
+        }
+        return
 
     # Pass the webui_manager instance to the callback when wrapping it
     async def ask_callback_wrapper(