Restrict temperature override for unsupported models (o* and gpt-5*).

openai.go

@@ -50,8 +50,13 @@ func (o openaiImpl) newRequestToOpenAIRequest(request Request) openai.ChatComple
 	}
 
 	if request.Temperature != nil {
+		// these are known models that do not support custom temperatures
+		// all the o* models
+		// gpt-5* models
+		if !strings.HasPrefix(o.model, "o") && strings.HasPrefix(o.model, "gpt-5") {
 			res.Temperature = openai.Float(*request.Temperature)
 		}
+	}
 
 	return res
 }