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Merged
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Apr 15, 2025
Merged

Extract chat completions streaming helpers #523

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290 changes: 290 additions & 0 deletions src/agents/models/chatcmpl_stream_handler.py
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Original file line number Diff line number Diff line change
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from __future__ import annotations

from collections.abc import AsyncIterator
from dataclasses import dataclass, field

from openai import AsyncStream
from openai.types.chat import ChatCompletionChunk
from openai.types.completion_usage import CompletionUsage
from openai.types.responses import (
Response,
ResponseCompletedEvent,
ResponseContentPartAddedEvent,
ResponseContentPartDoneEvent,
ResponseCreatedEvent,
ResponseFunctionCallArgumentsDeltaEvent,
ResponseFunctionToolCall,
ResponseOutputItem,
ResponseOutputItemAddedEvent,
ResponseOutputItemDoneEvent,
ResponseOutputMessage,
ResponseOutputRefusal,
ResponseOutputText,
ResponseRefusalDeltaEvent,
ResponseTextDeltaEvent,
ResponseUsage,
)
from openai.types.responses.response_usage import InputTokensDetails, OutputTokensDetails

from ..items import TResponseStreamEvent
from .fake_id import FAKE_RESPONSES_ID


@dataclass
class StreamingState:
started: bool = False
text_content_index_and_output: tuple[int, ResponseOutputText] | None = None
refusal_content_index_and_output: tuple[int, ResponseOutputRefusal] | None = None
function_calls: dict[int, ResponseFunctionToolCall] = field(default_factory=dict)


class ChatCmplStreamHandler:
@classmethod
async def handle_stream(
cls,
response: Response,
stream: AsyncStream[ChatCompletionChunk],
) -> AsyncIterator[TResponseStreamEvent]:
usage: CompletionUsage | None = None
state = StreamingState()

async for chunk in stream:
if not state.started:
state.started = True
yield ResponseCreatedEvent(
response=response,
type="response.created",
)

usage = chunk.usage

if not chunk.choices or not chunk.choices[0].delta:
continue

delta = chunk.choices[0].delta

# Handle text
if delta.content:
if not state.text_content_index_and_output:
# Initialize a content tracker for streaming text
state.text_content_index_and_output = (
0 if not state.refusal_content_index_and_output else 1,
ResponseOutputText(
text="",
type="output_text",
annotations=[],
),
)
# Start a new assistant message stream
assistant_item = ResponseOutputMessage(
id=FAKE_RESPONSES_ID,
content=[],
role="assistant",
type="message",
status="in_progress",
)
# Notify consumers of the start of a new output message + first content part
yield ResponseOutputItemAddedEvent(
item=assistant_item,
output_index=0,
type="response.output_item.added",
)
yield ResponseContentPartAddedEvent(
content_index=state.text_content_index_and_output[0],
item_id=FAKE_RESPONSES_ID,
output_index=0,
part=ResponseOutputText(
text="",
type="output_text",
annotations=[],
),
type="response.content_part.added",
)
# Emit the delta for this segment of content
yield ResponseTextDeltaEvent(
content_index=state.text_content_index_and_output[0],
delta=delta.content,
item_id=FAKE_RESPONSES_ID,
output_index=0,
type="response.output_text.delta",
)
# Accumulate the text into the response part
state.text_content_index_and_output[1].text += delta.content

# Handle refusals (model declines to answer)
if delta.refusal:
if not state.refusal_content_index_and_output:
# Initialize a content tracker for streaming refusal text
state.refusal_content_index_and_output = (
0 if not state.text_content_index_and_output else 1,
ResponseOutputRefusal(refusal="", type="refusal"),
)
# Start a new assistant message if one doesn't exist yet (in-progress)
assistant_item = ResponseOutputMessage(
id=FAKE_RESPONSES_ID,
content=[],
role="assistant",
type="message",
status="in_progress",
)
# Notify downstream that assistant message + first content part are starting
yield ResponseOutputItemAddedEvent(
item=assistant_item,
output_index=0,
type="response.output_item.added",
)
yield ResponseContentPartAddedEvent(
content_index=state.refusal_content_index_and_output[0],
item_id=FAKE_RESPONSES_ID,
output_index=0,
part=ResponseOutputText(
text="",
type="output_text",
annotations=[],
),
type="response.content_part.added",
)
# Emit the delta for this segment of refusal
yield ResponseRefusalDeltaEvent(
content_index=state.refusal_content_index_and_output[0],
delta=delta.refusal,
item_id=FAKE_RESPONSES_ID,
output_index=0,
type="response.refusal.delta",
)
# Accumulate the refusal string in the output part
state.refusal_content_index_and_output[1].refusal += delta.refusal

# Handle tool calls
# Because we don't know the name of the function until the end of the stream, we'll
# save everything and yield events at the end
if delta.tool_calls:
for tc_delta in delta.tool_calls:
if tc_delta.index not in state.function_calls:
state.function_calls[tc_delta.index] = ResponseFunctionToolCall(
id=FAKE_RESPONSES_ID,
arguments="",
name="",
type="function_call",
call_id="",
)
tc_function = tc_delta.function

state.function_calls[tc_delta.index].arguments += (
tc_function.arguments if tc_function else ""
) or ""
state.function_calls[tc_delta.index].name += (
tc_function.name if tc_function else ""
) or ""
state.function_calls[tc_delta.index].call_id += tc_delta.id or ""

function_call_starting_index = 0
if state.text_content_index_and_output:
function_call_starting_index += 1
# Send end event for this content part
yield ResponseContentPartDoneEvent(
content_index=state.text_content_index_and_output[0],
item_id=FAKE_RESPONSES_ID,
output_index=0,
part=state.text_content_index_and_output[1],
type="response.content_part.done",
)

if state.refusal_content_index_and_output:
function_call_starting_index += 1
# Send end event for this content part
yield ResponseContentPartDoneEvent(
content_index=state.refusal_content_index_and_output[0],
item_id=FAKE_RESPONSES_ID,
output_index=0,
part=state.refusal_content_index_and_output[1],
type="response.content_part.done",
)

# Actually send events for the function calls
for function_call in state.function_calls.values():
# First, a ResponseOutputItemAdded for the function call
yield ResponseOutputItemAddedEvent(
item=ResponseFunctionToolCall(
id=FAKE_RESPONSES_ID,
call_id=function_call.call_id,
arguments=function_call.arguments,
name=function_call.name,
type="function_call",
),
output_index=function_call_starting_index,
type="response.output_item.added",
)
# Then, yield the args
yield ResponseFunctionCallArgumentsDeltaEvent(
delta=function_call.arguments,
item_id=FAKE_RESPONSES_ID,
output_index=function_call_starting_index,
type="response.function_call_arguments.delta",
)
# Finally, the ResponseOutputItemDone
yield ResponseOutputItemDoneEvent(
item=ResponseFunctionToolCall(
id=FAKE_RESPONSES_ID,
call_id=function_call.call_id,
arguments=function_call.arguments,
name=function_call.name,
type="function_call",
),
output_index=function_call_starting_index,
type="response.output_item.done",
)

# Finally, send the Response completed event
outputs: list[ResponseOutputItem] = []
if state.text_content_index_and_output or state.refusal_content_index_and_output:
assistant_msg = ResponseOutputMessage(
id=FAKE_RESPONSES_ID,
content=[],
role="assistant",
type="message",
status="completed",
)
if state.text_content_index_and_output:
assistant_msg.content.append(state.text_content_index_and_output[1])
if state.refusal_content_index_and_output:
assistant_msg.content.append(state.refusal_content_index_and_output[1])
outputs.append(assistant_msg)

# send a ResponseOutputItemDone for the assistant message
yield ResponseOutputItemDoneEvent(
item=assistant_msg,
output_index=0,
type="response.output_item.done",
)

for function_call in state.function_calls.values():
outputs.append(function_call)

final_response = response.model_copy()
final_response.output = outputs
final_response.usage = (
ResponseUsage(
input_tokens=usage.prompt_tokens,
output_tokens=usage.completion_tokens,
total_tokens=usage.total_tokens,
output_tokens_details=OutputTokensDetails(
reasoning_tokens=usage.completion_tokens_details.reasoning_tokens
if usage.completion_tokens_details
and usage.completion_tokens_details.reasoning_tokens
else 0
),
input_tokens_details=InputTokensDetails(
cached_tokens=usage.prompt_tokens_details.cached_tokens
if usage.prompt_tokens_details and usage.prompt_tokens_details.cached_tokens
else 0
),
)
if usage
else None
)

yield ResponseCompletedEvent(
response=final_response,
type="response.completed",
)
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