diff --git a/codex-cli/src/utils/responses.ts b/codex-cli/src/utils/responses.ts
index 99bbd7ee..6a763ebf 100644
--- a/codex-cli/src/utils/responses.ts
+++ b/codex-cli/src/utils/responses.ts
@@ -275,8 +275,8 @@ const createCompletion = (openai: OpenAI, input: ResponseCreateInput) => {
     messages: fullMessages,
     tools: chatTools,
     web_search_options: webSearchOptions,
-    temperature: input.temperature ?? 1.0,
-    top_p: input.top_p ?? 1.0,
+    temperature: input.temperature,
+    top_p: input.top_p,
     tool_choice: (input.tool_choice === "auto"
       ? "auto"
       : input.tool_choice) as OpenAI.Chat.Completions.ChatCompletionCreateParams["tool_choice"],
@@ -385,11 +385,11 @@ async function nonStreamResponses(
       parallel_tool_calls: input.parallel_tool_calls ?? false,
       previous_response_id: input.previous_response_id ?? null,
       reasoning: null,
-      temperature: input.temperature ?? 1.0,
+      temperature: input.temperature,
       text: { format: { type: "text" } },
       tool_choice: input.tool_choice ?? "auto",
       tools: input.tools ?? [],
-      top_p: input.top_p ?? 1.0,
+      top_p: input.top_p,
       truncation: input.truncation ?? "disabled",
       usage: chatResponse.usage
         ? {
@@ -471,11 +471,11 @@ async function* streamResponses(
     parallel_tool_calls: true,
     previous_response_id: input.previous_response_id ?? null,
     reasoning: null,
-    temperature: input.temperature ?? 1.0,
+    temperature: input.temperature,
     text: { format: { type: "text" } },
     tool_choice: input.tool_choice ?? "auto",
     tools: input.tools ?? [],
-    top_p: input.top_p ?? 1.0,
+    top_p: input.top_p,
     truncation: input.truncation ?? "disabled",
     usage: undefined,
     user: input.user ?? undefined,
@@ -652,11 +652,11 @@ async function* streamResponses(
       parallel_tool_calls: true,
       previous_response_id: input.previous_response_id ?? null,
       reasoning: null,
-      temperature: input.temperature ?? 1.0,
+      temperature: input.temperature,
       text: { format: { type: "text" } },
       tool_choice: input.tool_choice ?? "auto",
       tools: input.tools ?? [],
-      top_p: input.top_p ?? 1.0,
+      top_p: input.top_p,
       truncation: input.truncation ?? "disabled",
       usage: usage as ResponseOutput["usage"],
       user: input.user ?? undefined,