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Overview Graphs Functional API Pregel Checkpointing Storage Caching Types Runtime Config Errors Constants Channels Agents

LangGraph Checkpoint

Checkpoint Postgres

Checkpoint SQLite

LangGraph Prebuilt

LangGraph Supervisor

LangGraph Swarm

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Pythonlanggraphstream_typesStreamTransformerfail

Method●Since v1.1

fail

Copy

fail(
    self,
    err: BaseException,
) -> None

View source on GitHub

Parameters

Name	Type	Description
`err`*	`BaseException`	The exception that ended the run.

Called when the run ends with an error (sync lane).

Override to fail StreamChannels, reject promises, or perform other teardown. StreamChannel instances in the projection dict are auto-failed by the mux.