[BUG] o4-mini usage raising stop parameter not support exception

[tspecht]

Description

When attempting to use o4-mini as the Model for an agent, the OpenAI API returns an error indicating that the stop parameter is not supported.

Stacktrace:

File "/usr/local/lib/python3.12/site-packages/crewai/agents/crew_agent_executor.py", line 208, in _invoke_loop
    raise e
  File "/usr/local/lib/python3.12/site-packages/crewai/agents/crew_agent_executor.py", line 155, in _invoke_loop
    answer = get_llm_response(
             ^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/crewai/utilities/agent_utils.py", line 157, in get_llm_response
    raise e
  File "/usr/local/lib/python3.12/site-packages/crewai/utilities/agent_utils.py", line 148, in get_llm_response
    answer = llm.call(
             ^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/crewai/llm.py", line 794, in call
    return self._handle_non_streaming_response(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/agents/utilities.py", line 90, in _handle_non_streaming_response
    return super()._handle_non_streaming_response(params, callbacks, available_functions)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/crewai/llm.py", line 630, in _handle_non_streaming_response
    response = litellm.completion(**params)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/litellm/utils.py", line 1154, in wrapper
    raise e
  File "/usr/local/lib/python3.12/site-packages/litellm/utils.py", line 1032, in wrapper
    result = original_function(*args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/litellm/main.py", line 3068, in completion
    raise exception_type(
          ^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/litellm/litellm_core_utils/exception_mapping_utils.py", line 2201, in exception_type
    raise e
  File "/usr/local/lib/python3.12/site-packages/litellm/litellm_core_utils/exception_mapping_utils.py", line 326, in exception_type
    raise BadRequestError(
litellm.exceptions.BadRequestError: litellm.BadRequestError: OpenAIException - Error code: 400 - {'error': {'message': "Unsupported parameter: 'stop' is not supported with this model.", 'type': 'invalid_request_error', 'param': 'stop', 'code': 'unsupported_parameter'}}

Code that adds the erroneous parameter:

crewAI/src/crewai/llm.py

Line 341 in 6d0039b

"stop": self.stop,

Solution:
By removing the stop parameter in a custom LLM subclass the issue goes away. Example:

class LLMWithFixedStopWords(LLM):
       def _handle_streaming_response(self, params, callbacks, available_functions):
           if "o4-mini" in self.model:
               params.pop("stop", None)
           return super()._handle_streaming_response(params, callbacks, available_functions)

       def _handle_non_streaming_response(self, params, callbacks, available_functions):
           if "o4-mini" in self.model:
               params.pop("stop", None)
           return super()._handle_non_streaming_response(params, callbacks, available_functions)

Steps to Reproduce

1. Create any agent that uses o4-mini as the model
2. Run the agent with any task

Expected behavior

Agent runs successfully

Screenshots/Code snippets

See in description

Operating System

Ubuntu 20.04

Python Version

3.11

crewAI Version

0.114

crewAI Tools Version

N/A

Virtual Environment

Venv

Evidence

See description

Possible Solution

See description

Additional context

See description

[lucasgomide]

hey @tspecht

I gotcha the same issue last week with other models at all. I hope push a solution by the end of the week

[justinsyu]

Hey Everyone,

This is what I did and it allows the calls to the models to go through:

# Patch for BadRequestError: Error code: 400 - {'error': {'message': "Unsupported parameter: 'stop' is not supported with this model.", 'type': 'invalid_request_error', 'param': 'stop', 'code': 'unsupported_parameter'}}

# ── 1. Imports ──────────────────────────────────────────────────────────────
from google.colab import userdata
import os
import litellm
# Whatever wrapper you’re using:
from crewai import LLM          # ⬅️ or `from langchain_openai import ChatOpenAI as LLM`

# ── 2. Monkey-patch LiteLLM to strip the unsupported `stop` field ───────────
original_completion = litellm.completion

def patched_completion(*args, **kwargs):
    if "stop" in kwargs:
        print("Removing 'stop' parameter from LiteLLM call …")
        kwargs.pop("stop")
    return original_completion(*args, **kwargs)

litellm.completion = patched_completion   # <--  Patch must happen *before* any LLM is instantiated

# ── 3. API key ──────────────────────────────────────────────────────────────
os.environ["OPENAI_API_KEY"] = userdata.get("openai_api_key")

# ── 4. LLM instances ────────────────────────────────────────────────────────
llm_model = "gpt-4o"           # preview model

my_llm = LLM(
    model=llm_model,
    temperature="high",
    api_key=os.environ["OPENAI_API_KEY"]
)

my_llm2 = LLM(
    model="o3",
    temperature="high",
    api_key=os.environ["OPENAI_API_KEY"]
)

my_llm3 = LLM(
    model="o1",
    temperature="high",
    api_key=os.environ["OPENAI_API_KEY"]
)

[lucasgomide]

just submitted this PR to address that
https://github.com/crewAIInc/crewAI/pull/2742/files

Now you can simply set stop=None directly in your LLM to remove this flag from LiteLLM calls