LangChain Reference home page

GitHub
Main Docs

LangGraph Checkpoint

LangGraph Store

Checkpoint Postgres

Store Postgres

Checkpoint SQLite

LangGraph Prebuilt

LangGraph CLI

LangGraph SDK

LangGraph Supervisor

LangGraph Swarm

⌘I

LangChain Assistant

Ask a question to get started

Enter to send•Shift+Enter new line

Menu

LangGraph Checkpoint

LangGraph Store

Checkpoint Postgres

Checkpoint SQLite

LangGraph Prebuilt

LangGraph Supervisor

LangGraph Swarm

Language

Theme

Pythonlanggraph-sdkstreamsync_controllerSyncStreamController

Class●Since v0.4

SyncStreamController

Copy

SyncStreamController(
  self,
  transport: SyncProtocolTransport,
  *,
  run_start_gate: threading.Event | None =

Constructors

Methods

View source on GitHub

None

,

run_start_timeout

:

=

_DEFAULT_RUN_START_TIMEOUT

,

max_reconnect_attempts

:

=

5

,

reconnect_backoff_base

:

=

0.1

,

reconnect_backoff_cap

:

=

10.0

)

constructor

__init__

Name	Type
transport	SyncProtocolTransport
run_start_gate	threading.Event \| None
run_start_timeout	float
max_reconnect_attempts	int
reconnect_backoff_base	float
reconnect_backoff_cap	float

register_subscription

unregister_subscription

Wake every active subscription iterator on interrupt (run pause).

Pushes the terminal sentinel (None) into every subscription queue. Iterators see None and return; the shared SSE keeps running so re-iteration after run.respond(...) registers a fresh subscription and resumes.

reconcile_stream

ensure_fanout_running

observe_applied_through_seq

Advance the reconnect cursor from a command response meta sequence.

Owns the sync shared SSE handle, subscription registry, and fan-out thread.