GPT-5-Mini Responses API Empty Output Text Issue

API Bugs
, ,
1

:lady_beetle: GPT-5-Mini Responses API — output_text Empty (Model Output Structure Bug)

Issue Description

When using gpt-5-mini with the OpenAI Responses API, the output_text field returns an empty string ("") even though the API call succeeds.
This is not an SDK parsing issue — the model’s response currently contains only a reasoning item and no message item, so output_text cannot be populated.

Expected Behavior

response.output_text should contain the model’s generated text, same as gpt-4o-mini.

Actual Behavior

  • response.output_text → "" (empty)

  • response.output[0].type → "reasoning"

  • No ResponseOutputMessage is returned — only a ResponseReasoningItem.

Reproduction

from openai import AsyncOpenAI

client = AsyncOpenAI()

response = await client.responses.create(
    model="gpt-5-mini",
    input=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "Say hello in one sentence."}
    ],
    max_output_tokens=50,
)

print(f"output_text: '{response.output_text}'")  # Empty!
print(f"output[0] type: {response.output[0].type}")  # reasoning

Comparison Table

Model output_text output[0].type Status
gpt-5-mini "" reasoning :cross_mark: Broken
gpt-4o-mini "Hello! How can I assist you today?" message :white_check_mark: Works

Root Cause

The gpt-5-mini model omits a message output item in some responses, returning only reasoning.
Since output_text is built from message items, it will be empty unless text output is explicitly requested.

Temporary Workaround

Force the output format to text so the model returns a message item:

response = await client.responses.create(
    model="gpt-5-mini",
    input=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "Say hello in one sentence."}
    ],
    text={"format": {"type": "text"}},
    max_output_tokens=200,
)

print(response.output_text)  # Works now

Verified Fix Results

With the workaround:

  • output_text is populated correctly

  • output contains both reasoning and message items

  • Matches expected behavior from gpt-4o-mini

Environment

  • OS: Windows 11

  • Python: 3.11

  • OpenAI Python SDK: Latest

  • Affected Model: gpt-5-mini (likely other gpt-5 family models)

  • Works Fine On: gpt-4o-mini

2

Also happens with Rest API

3

You have a root cause, no?

(this is why you should be careful just cut & pasting from ChatGPT or equivalent)

4

Sorry I confirmed with them on Github that it’s not a Python SDK Issue.

But the issue is real.

1 Like
5

Has this been fixed? Im really confused