[BUG] Responses API streaming drops tool calls when available_functions is None, returning "" instead of the function-call list

Description

With api="responses" and stream=True, OpenAICompletion._handle_streaming_responses accumulates function calls from response.output_item.done events but only ever acts on them under if function_calls and available_functions:. There is no branch for the available_functions is None case, which is exactly the contract CrewAgentExecutor uses (it passes available_functions=None and executes the tools itself). The accumulated calls are discarded, the method falls through to the LLMCallCompletedEvent(LLM_CALL) path and returns the streamed text — an empty string for a pure tool-call turn.

The non-streaming sibling _handle_responses handles this correctly at the same call site (if function_calls and not available_functions: ... return function_calls), as does the chat-completions streaming path. Only the Responses streaming handlers are missing the branch.

Root cause: lib/crewai/src/crewai/llms/providers/openai/completion.py:1436 (sync) and :1573 (async twin _ahandle_streaming_responses).

Steps to Reproduce

1. Configure LLM(model="gpt-5.5", api="responses", stream=True) on an agent that has at least one tool.
2. Let CrewAgentExecutor invoke the LLM. It calls with tools=openai_tools and available_functions=None (lib/crewai/src/crewai/agents/crew_agent_executor.py:542-543, and the same at :1340-1341), then requires a list back.
3. The model returns a function_call item.
4. _call_responses dispatches on self._effective_stream() into _handle_streaming_responses, which reaches the guard at line 1436 and drops the call.

Minimal handler-level reproduction (no network; the OpenAI client is faked):

from types import SimpleNamespace
from crewai.llms.providers.openai.completion import OpenAICompletion

FUNCTION_CALL_ITEM = SimpleNamespace(
    type="function_call", id="fc_1", call_id="call_abc",
    name="multiply", arguments='{"a": 17, "b": 23}', status="completed",
)

RESPONSE = SimpleNamespace(
    id="resp_1", status="completed",
    output=[FUNCTION_CALL_ITEM], output_text="",
    usage=SimpleNamespace(input_tokens=10, output_tokens=5, total_tokens=15,
                          input_tokens_details=None, output_tokens_details=None),
)

def stream_events():
    yield SimpleNamespace(type="response.created", response=RESPONSE)
    yield SimpleNamespace(type="response.output_item.done", item=FUNCTION_CALL_ITEM)
    yield SimpleNamespace(type="response.completed", response=RESPONSE)

class FakeResponses:
    def __init__(self, streaming): self.streaming = streaming
    def create(self, **kwargs):
        return stream_events() if self.streaming else RESPONSE

class FakeClient:
    def __init__(self, streaming): self.responses = FakeResponses(streaming)

def build(**kw):
    return OpenAICompletion(model="gpt-5.5", api_key="sk-test", api="responses", **kw)

llm = build(stream=False)
llm._get_sync_client = lambda: FakeClient(False)
nonstream = llm._handle_responses(
    params={"input": [{"role": "user", "content": "multiply"}]}, available_functions=None)
print("non-streaming ->", type(nonstream).__name__, nonstream)

llm = build(stream=True)
llm._get_sync_client = lambda: FakeClient(True)
streamed = llm._handle_streaming_responses(
    params={"input": [{"role": "user", "content": "multiply"}]}, available_functions=None)
print("streaming     ->", type(streamed).__name__, repr(streamed))

Full script kept at /tmp/repro_openai_responses_stream_tools.py.

Expected behavior

For a pure tool-call turn, streaming should return the same value the non-streaming path returns: the list of function calls, so the caller (the executor) can run them.

Concrete basis, all in the same class:

• Non-streaming Responses sibling, completion.py:1113: if function_calls and not available_functions: → emit LLMCallCompletedEvent(call_type=LLMCallType.TOOL_CALL) and return function_calls. The async twin at :1260 is identical.
• Chat-completions streaming, completion.py:2061-2062: comment "Without available_functions, return tool_calls so the caller (executor) handles execution", then if message.tool_calls and not available_functions: ... return list(message.tool_calls); same block at :2499-2500 in _finalize_streaming_response, whose docstring states: "Returns: Tool calls list when tools were invoked without available_functions, tool execution result when available_functions is provided, or the text response string."
• The executor contract, lib/crewai/src/crewai/agents/crew_agent_executor.py:551-561: it passes available_functions=None, then requires isinstance(answer, list) and self._is_tool_call_list(answer) to run _handle_native_tool_calls.
• The error surfaces from lib/crewai/src/crewai/utilities/agent_utils.py ("Invalid response from LLM call - None or empty."), or the agent silently returns a blank answer.

The streaming Responses handlers (:1436, :1573) use if function_calls and available_functions: with no falsy branch, so this path is the odd one out.

Screenshots/Code snippets

Verbatim output, verifier 1:

stream=False -> list  [{'id': 'call_abc', 'name': 'multiply', 'arguments': '{"a": 17, "b": 23}'}] (create calls=1, tools sent=True)
stream=True  -> str   '' (create calls=1, tools sent=True)
stream=False executor gets: [{'id': 'call_abc', 'name': 'multiply', 'arguments': '{"a": 17, "b": 23}'}]
stream=True  executor RAISES: ValueError: Invalid response from LLM call - None or empty.
(patched) stream=True -> list [{'id': 'call_abc', 'name': 'multiply', 'arguments': '{"a": 17, "b": 23}'}]
(patched) pytest tests/llms/openai tests/llms/test_tool_call_streaming.py: 204 passed, 4 failed, 1 skipped

Verbatim output, verifier 2:

================ stream=False ================
RESULT -> 'The answer is 391.'
create() calls: 2 | multiply() ran: [(17, 23)]

================ stream=True ================
RAISED -> ValueError Invalid response from LLM call - None or empty.
create() calls: 3 | multiply() ran: []

Operating System

Other (specify in additional context) — macOS 26.6.2 (Darwin 25.6.0)

Python Version

3.13

crewAI Version

1.15.21 (commit 9393a47f313a0544db15693db9bcc48585f30ef5)

crewAI Tools Version

Not installed / not involved in the reproduction (1.15.21 available in the same environment). The defect is in crewai core; no crewai-tools code is on the path.

Virtual Environment

Venv

Evidence

Environment: crewAI 1.15.21 @ 9393a47f313a0544db15693db9bcc48585f30ef5, openai 2.41.0, Python 3.13.15, macOS 26.6.2, uv venv.

An independent run on a clean checkout of the commit above gives:

non-streaming -> list [{'id': 'call_abc', 'name': 'multiply', 'arguments': '{"a": 17, "b": 23}'}]
streaming     -> str ''

The _handle_responses / _handle_streaming_responses pair differs only in the missing not available_functions branch. Applying the mirror branch to both _handle_streaming_responses and _ahandle_streaming_responses makes the streaming case return the same list, with the existing openai provider tests unchanged in outcome.

Related reports found while checking for duplicates:

• Issue #7438 + PR #7439 — Bedrock streaming drops native tool calls (same defect class, different provider).
• PR #4444 — chat-completions streaming returns tool calls when available_functions is None; patches _handle_streaming_completion / _ahandle_streaming_completion only. It does not touch _handle_streaming_responses or _ahandle_streaming_responses, so the Responses path remains uncovered.
• Closed #7486 / #7243 / #4442. No existing issue or PR covers the OpenAI Responses streaming path.

Possible Solution

Mirror the non-streaming sibling before the if function_calls and available_functions: block in both _handle_streaming_responses and _ahandle_streaming_responses: when function_calls is non-empty and available_functions is falsy, emit LLMCallCompletedEvent(call_type=LLMCallType.TOOL_CALL, response=function_calls, ...) and return function_calls — the same shape as completion.py:1113 and :2500. Plus a regression test covering the streaming Responses handler with available_functions=None.

Happy to open a PR with this approach.

Additional context

AI disclosure: this issue was authored by an AI agent. Per .github/CONTRIBUTING.md it carries the llm-generated label; I tried to apply it, but adding labels requires write access this account does not have (AddLabelsToLabelable permission error), so a maintainer will need to add it.

Start in lib/crewai/src/crewai/llms/providers/openai/completion.py at _handle_streaming_responses and _ahandle_streaming_responses, comparing them with _handle_responses and the chat-completions streaming path. Reproduce the pure tool-call case with available_functions=None, then add coverage for both streaming handlers and verify they return the function-call list and emit the existing tool-call completion event.