gpt-5.3-codex intermittently leaks malformed tool-call text and stops mid-run #15164

Summary

When using openai/gpt-5.3-codex in OpenCode, the assistant intermittently emits malformed internal tool-call text into the user-facing response and appears to stop mid-task. The same workflow is stable with openai/gpt-5.2-codex.

Environment

• OpenCode: 1.2.14
• OS: macOS 26.2 (Build 25C56)
• Node: v25.6.1
• Model: openai/gpt-5.3-codex

What I expected

• The assistant should finish the task and return only the final requested output.
• Internal tool-call payloads should never appear in the answer text.

What actually happens

• During multi-step fetch/extract tasks, the response sometimes contains internal-looking tool call text (example below), then appears to stop:

... `config.json`에서 `reasoningEffort` 키 위치를 좁혀서 허용값(enum)만 확인하겠습니다. +#+#+#+#+#+assistant to=functions.grep մեկնաբանություն ...
{"pattern":"reasoningEffort","path":"/Users/.../tool-output",...}

• In affected runs, the conversation shows repeated finish=tool-calls then a premature finish=stop with incomplete intermediate text.
• This was observed both before and after removing MCP servers from config.

Reproduction (example)

1. Set model to openai/gpt-5.3-codex.
2. Run:

opencode run "다음 3개 공식 문서 URL만 사용해서 reasoningEffort 허용 값만 추출해줘. 1) https://opencode.ai/docs/models/ 2) https://opencode.ai/config.json 3) https://platform.openai.com/docs/guides/reasoning 규칙: - 위 3개 URL 외 다른 출처는 사용하지 마. - 중간 과정, 내부 실행 로그, 도구 호출 문자열은 출력하지 마. - 최종 결과만 출력해."

3. Observe occasional malformed tool-call text leakage + apparent mid-run stop.

Control / workaround

• Switching only the model to openai/gpt-5.2-codex removes the issue in my tests.
• Forcing a single bash-only execution path also reduces occurrence.

Notes

I can provide sanitized session exports and exact timestamps if helpful.