> ## Documentation Index
> Fetch the complete documentation index at: https://gofastmcp.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# lifespan

# `fastmcp.server.mixins.lifespan`

Lifespan infrastructure for FastMCP Server.

## Classes

### `LifespanMixin` <sup>[https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp\_slim/fastmcp/server/mixins/lifespan.py#L39](https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/mixins/lifespan.py#L39)</sup>

Mixin providing lifespan infrastructure for FastMCP.

**Methods:**

#### `docket` <sup>[https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp\_slim/fastmcp/server/mixins/lifespan.py#L43](https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/mixins/lifespan.py#L43)</sup>

```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
docket(self: FastMCP) -> Docket | None
```

The Docket instance owned by this server, if the tasks extension is active.

Returns the Docket that the tasks extension initialized as the root of a
runtime tree, or None when no task backend is running. Mounted children do
not own their own Docket — they share the root's via `_current_docket`
ContextVar inheritance — so accessing `.docket` on a mounted child
returns None even while its tasks run on the root's Docket.


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