MCP channels let a server push messages into the session - deploy finished, alert fired, task completed - instead of waiting for Claude to poll.

What it does

The server opens a channel with a name and topic. When events happen server-side, it sends messages into the Claude Code session. The model sees them as they arrive and can react in the current or next turn. This reverses the usual request-response flow and opens up real-time integrations.

When to use it

Long-running jobs where "tell me when done" is more efficient than polling.
Alert and observability integrations that should surface in-session.
Chat or collaboration bridges where messages arrive without being asked.
Build/deploy dashboards that push status rather than expose an endpoint.

Gotchas

Channel messages interrupt the conversation flow. Noisy channels are distracting.
Backpressure matters - a server that spams can wedge a session.
Not every client supports channels yet. Check client compatibility when designing.

Official docs: https://code.claude.com/docs/en/mcp.md#push-messages-with-channels