What happened?

When calling litellm.responses() with chatgpt/gpt-5.4, the response returns output=[] with status='completed', meaning the model ran successfully but no output was captured.

Debug logs show that ChatGPT returns a proper SSE stream including response.output_item.added events, but LiteLLM fails to parse them and crashes with ValueError: Unknown items in responses API response: [] when called via litellm.completion().

Steps to reproduce

``` import litellm

# This returns output=[] with status='completed' response = litellm.responses( model='chatgpt/gpt-5.4', input=[{'type': 'message', 'role': 'user', 'content': 'hi'}] ) print(response.output) # [] print(response.status) # completed

# This crashes entirely import litellm response = litellm.completion( model='chatgpt/gpt-5.4', messages=[{'role': 'user', 'content': 'hi'}] ) # ValueError: Unknown items in responses API response: [] ```

Expected behavior output should contain the model's response text. litellm.completion() should not crash. Actual behavior

litellm.responses() returns output=[] despite status='completed' and non-zero usage.output_tokens=12 litellm.completion() raises ValueError: Unk…