Invocations sent to gpt-5-nano via ChatOpenAI.ainvoke() come back without errors but always with an empty content

[fantauzzi]

Checked other resources

• This is a bug, not a usage question. For questions, please use the LangChain Forum (https://forum.langchain.com/).
• I added a clear and descriptive title that summarizes this issue.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).
• I read what a minimal reproducible example is (https://stackoverflow.com/help/minimal-reproducible-example).
• I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS.

Example Code

import asyncio
from langchain_openai import ChatOpenAI
from langchain.schema import HumanMessage


async def main():
    prompt = ('Tell me a dad joke')

    llm = ChatOpenAI(model="gpt-5-nano", temperature=1, max_tokens=500)  # <== this gets an empty string in response.content
    # llm = ChatOpenAI(model="gpt-4.1-nano", temperature=1, max_tokens=500)  # <== This would work OK
    response = await llm.ainvoke([HumanMessage(content=prompt)])
    print(response.content)


asyncio.run(main())

Error Message and Stack Trace (if applicable)

No response

Description

I am using LangChain to send prompts to different LLM APIs with almost the same code. I call ainvoke() on instances of ChatOpenAI to send my prompts to different OpenAI models. WIth older models it works correctly, but when I send a prompt to gpt-5-nano the content attribute of ainvoke()'s return value is always an empty string.

Note that if I send the same prompt to gpt-5-nano via the command line, I get a meaningful response. E.g.

⮕ curl https://api.openai.com/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -d '{
    "model": "gpt-5-nano",
    "messages": [
      {"role": "user", "content": "Tell me a dad joke"}
    ]
  }' \
  | jq -r '.choices[0].message.content'
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   978  100   866  100   112    211     27  0:00:04  0:00:04 --:--:--   238
Here's a dad joke for you: I'm reading a book on anti-gravity. It's impossible to put down.

System Info

System Information
------------------
> OS:  Linux
> OS Version:  #27~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Tue Jul 22 17:38:49 UTC 2
> Python Version:  3.13.5 (main, Jul 23 2025, 18:18:31) [GCC 13.3.0]

Package Information
-------------------
> langchain_core: 0.3.74
> langchain: 0.3.27
> langchain_community: 0.3.27
> langsmith: 0.4.13
> langchain_anthropic: 0.3.18
> langchain_huggingface: 0.3.1
> langchain_openai: 0.3.29
> langchain_text_splitters: 0.3.9

Optional packages not installed
-------------------------------
> langserve

Other Dependencies
------------------
> aiohttp<4.0.0,>=3.8.3: Installed. No version info available.
> anthropic<1,>=0.60.0: Installed. No version info available.
> async-timeout<5.0.0,>=4.0.0;: Installed. No version info available.
> dataclasses-json<0.7,>=0.5.7: Installed. No version info available.
> httpx-sse<1.0.0,>=0.4.0: Installed. No version info available.
> httpx<1,>=0.23.0: Installed. No version info available.
> huggingface-hub>=0.33.4: Installed. No version info available.
> jsonpatch<2.0,>=1.33: Installed. No version info available.
> langchain-anthropic;: Installed. No version info available.
> langchain-aws;: Installed. No version info available.
> langchain-azure-ai;: Installed. No version info available.
> langchain-cohere;: Installed. No version info available.
> langchain-community;: Installed. No version info available.
> langchain-core<1.0.0,>=0.3.66: Installed. No version info available.
> langchain-core<1.0.0,>=0.3.70: Installed. No version info available.
> langchain-core<1.0.0,>=0.3.72: Installed. No version info available.
> langchain-core<1.0.0,>=0.3.74: Installed. No version info available.
> langchain-deepseek;: Installed. No version info available.
> langchain-fireworks;: Installed. No version info available.
> langchain-google-genai;: Installed. No version info available.
> langchain-google-vertexai;: Installed. No version info available.
> langchain-groq;: Installed. No version info available.
> langchain-huggingface;: Installed. No version info available.
> langchain-mistralai;: Installed. No version info available.
> langchain-ollama;: Installed. No version info available.
> langchain-openai;: Installed. No version info available.
> langchain-perplexity;: Installed. No version info available.
> langchain-text-splitters<1.0.0,>=0.3.9: Installed. No version info available.
> langchain-together;: Installed. No version info available.
> langchain-xai;: Installed. No version info available.
> langchain<1.0.0,>=0.3.26: Installed. No version info available.
> langsmith-pyo3>=0.1.0rc2;: Installed. No version info available.
> langsmith>=0.1.125: Installed. No version info available.
> langsmith>=0.1.17: Installed. No version info available.
> langsmith>=0.3.45: Installed. No version info available.
> numpy>=1.26.2;: Installed. No version info available.
> numpy>=2.1.0;: Installed. No version info available.
> openai-agents>=0.0.3;: Installed. No version info available.
> openai<2.0.0,>=1.86.0: Installed. No version info available.
> opentelemetry-api>=1.30.0;: Installed. No version info available.
> opentelemetry-exporter-otlp-proto-http>=1.30.0;: Installed. No version info available.
> opentelemetry-sdk>=1.30.0;: Installed. No version info available.
> orjson>=3.9.14;: Installed. No version info available.
> packaging>=23.2: Installed. No version info available.
> pydantic-settings<3.0.0,>=2.4.0: Installed. No version info available.
> pydantic<3,>=1: Installed. No version info available.
> pydantic<3.0.0,>=2.7.4: Installed. No version info available.
> pydantic>=2.7.4: Installed. No version info available.
> pytest>=7.0.0;: Installed. No version info available.
> PyYAML>=5.3: Installed. No version info available.
> requests-toolbelt>=1.0.0: Installed. No version info available.
> requests<3,>=2: Installed. No version info available.
> requests>=2.0.0: Installed. No version info available.
> rich>=13.9.4;: Installed. No version info available.
> sentence-transformers>=2.6.0;: Installed. No version info available.
> SQLAlchemy<3,>=1.4: Installed. No version info available.
> tenacity!=8.4.0,<10,>=8.1.0: Installed. No version info available.
> tenacity!=8.4.0,<10.0.0,>=8.1.0: Installed. No version info available.
> tiktoken<1,>=0.7: Installed. No version info available.
> tokenizers>=0.19.1: Installed. No version info available.
> transformers>=4.39.0;: Installed. No version info available.
> typing-extensions>=4.7: Installed. No version info available.
> vcrpy>=7.0.0;: Installed. No version info available.
> zstandard>=0.23.0: Installed. No version info available.

[onestardao]

this behavior matches No.6 – Logic Collapse & Recovery from my failure map.
the call path is valid, but the reasoning chain hits a dead-end and returns an empty payload without triggering an explicit error.
i have a MIT-licensed patch for this failure mode (already field-tested, with a star from the tesseract.js author).
if you’re curious, i can share the doc that explains how to fix it step-by-step.

[alexferrari88]

I can confirm the bug as I am experiencing it as well

[siddarthreddygsr]

I am facing this issue only in ainvoke