# 104005: Session send failed

Identifier: `session_send_failed`



An AI Transport send or steer could not be delivered. Either publishing it to the channel failed, or, in the Vercel chat transport, the HTTP POST to the agent endpoint failed with a network error or a non-2xx response.

## What you should do

This fails in one of two ways:

- **A channel publish failed** (a `send` or a `steer`). Inspect the `cause`, which carries the underlying publish failure and its own error code, for what went wrong and how to fix it.
- **The Vercel chat transport's HTTP POST failed.** The request to your agent-invocation endpoint returned a non-2xx response, surfaced with the status the endpoint returned, or errored outright. Check that the endpoint is reachable and returns a 2xx.

Neither a send nor a steer is retried automatically, so reissue it once the underlying problem is resolved.

## Why it happens

A send or steer publishes to the channel; in the Vercel chat transport a send instead POSTs to your agent-invocation endpoint, which publishes on the agent's behalf. This error is the non-permission failure of either path (a permission failure is reported separately as a capability error). The originating failure is preserved as the `cause` where available.

## What you'll see

The error is reported with code 104005. Its status is 500 for a failed channel publish; for a non-2xx POST it is the status the agent endpoint returned. Messages take the form `unable to publish events; ...`, `unable to publish steer; ...`, or `unable to send; HTTP POST to ... returned ...`.