enable_thinking and assistant prefill cannot be enabled at the same time

Author: matteoserva

tools/server/utils.hpp

@@ -749,6 +749,10 @@ static json oaicompat_completion_params_parse(
             throw std::runtime_error("Cannot have 2 or more assistant messages at the end of the list.");
         }
 
+        if(inputs.chat_template_kwargs.find("enable_thinking") != inputs.chat_template_kwargs.end()) {
+            throw std::runtime_error("Assistant response prefill is incompatible with enable_thinking.");
+        }
+
         inputs.extract_reasoning = false;
         inputs.add_generation_prompt = true;
     }