# 104004: Session already closed

Identifier: `session_closed`



An operation was attempted on an AI Transport session, view, or encoder that has already been closed. Once closed, these cannot send, receive, or be reopened.

## What you should do

Do not reuse a closed session, view, or encoder. Create a new session, and from it a new view or encoder, for any further work. If close is racing an in-flight operation, where the operation was started just as the session began closing, guard your code so it does not act on a session it has already closed.

## Why it happens

Sessions, views, and encoders are single-use; closing one is terminal. This error is raised when an operation, such as connect, send, create a view, regenerate, edit, steer, or write, is invoked on an instance that is already closed, or when an operation was awaiting a result that close then discarded.

## What you'll see

The error is reported with code 104004 and status 400. The message states which operation was attempted on which closed component, for example `unable to send; session is closed`, `unable to create view; session is closed`, or `unable to write to encoder; encoder has been closed`.