Implementation:Langchain ai Langchain BaseChatModel Should Stream

Knowledge Sources	LangChain
Domains	Control_Flow, Streaming
Last Updated	2026-02-11 00:00 GMT

Overview

Concrete tool for determining the streaming execution path provided by langchain-core.

Description

The BaseChatModel._should_stream() method inspects the model's configuration and capabilities to decide whether to use streaming. It checks whether the subclass has overridden _stream() or _astream(), respects the disable_streaming flag, and handles the special case of disabling streaming only during tool calling.

Usage

This is an internal method. It is called within invoke() to determine whether to use _generate() or _stream() for processing the request.

Code Reference

Source Location

• Repository: langchain
• File: libs/core/langchain_core/language_models/chat_models.py
• Lines: L439-477

Signature

def _should_stream(
    self,
    *,
    async_api: bool,
    run_manager: CallbackManagerForLLMRun
    | AsyncCallbackManagerForLLMRun
    | None = None,
    **kwargs: Any,
) -> bool:

Import

# Internal method — accessed via BaseChatModel instance
from langchain_core.language_models import BaseChatModel

I/O Contract

Inputs

Name	Type	Required	Description
async_api	bool	Yes	Whether the async API path is being used
run_manager	CallbackManagerForLLMRun or None	No	Callback manager for the current run
**kwargs	Any	No	Additional keyword arguments (checked for tool binding)

Outputs

Name	Type	Description
return	bool	True if streaming path should be used, False for non-streaming

Usage Examples

Controlling Streaming Behavior

from langchain_openai import ChatOpenAI

# Streaming is enabled by default when _stream() is implemented
llm = ChatOpenAI(model="gpt-4o-mini")

# Disable streaming entirely
llm = ChatOpenAI(model="gpt-4o-mini", disable_streaming=True)

# Disable streaming only during tool calling
llm = ChatOpenAI(model="gpt-4o-mini", disable_streaming="tool_calling")

Related Pages

Implements Principle

• Principle:Langchain_ai_Langchain_Streaming_Routing