Empty tool_calls array still triggers Tool Call handling

[sung1-kang]

What version of Codex is running?

0.0.0-dev

Which model were you using?

Qwen3-235B-A22B or custom models with vllm v0.9.0.1

What platform is your computer?

Darwin 24.5.0 arm64 arm

What steps can reproduce the bug?

1. Serve Qwen3 with vLLM: Set up and run Qwen3 using vLLM for serving.
2. Provide "hello" as input via codex message.

What is the expected behavior?

it should recognize "hello" as a standard conversational input and provide a simple, appropriate textual response as a greeting.

What do you see instead?

Instead of a greeting, the system incorrectly interprets "hello" as a tool call. Consequently, it executes no further action and produces no output whatsoever.

Additional information

Here's a suggested change to address this issue:

diff --git a/codex-cli/src/utils/responses.ts b/codex-cli/src/utils/responses.ts
index f0586ba..31ea847 100644
--- a/codex-cli/src/utils/responses.ts
+++ b/codex-cli/src/utils/responses.ts
@@ -493,7 +493,7 @@ async function* streamResponses(
     }
     if (
       !isToolCall &&
-      (("tool_calls" in choice.delta && choice.delta.tool_calls) ||
+      (("tool_calls" in choice.delta && choice.delta.tool_calls && choice.delta.tool_calls.length > 0) ||
         choice.finish_reason === "tool_calls")
     ) {
       isToolCall = true;

Explanation of the Change
The provided git diff shows a modification to the streamResponses asynchronous generator function within codex-cli/src/utils/responses.ts.

Specifically, the change refines the condition that determines if a tool_calls event is being processed. Previously, isToolCall would become true if choice.delta contained a tool_calls property, even if that tool_calls array was empty.