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

# Sessions

> How a Sedata-instrumented MCP server tracks a session lifecycle.

A **session** in `@sedata-ai/mcp` is a single instrumented process. It begins
when `instrumentServer` is called and ends when `telemetry.shutdown()` runs.

## Session id

`TelemetryManager` mints one UUID per process and adds it to every span and
every metric as `mcp.session.id`.

```text theme={null}
mcp.session.id = "f3a4b9c2-..." // constant for the lifetime of the process
```

You'll see this attribute on:

* every span produced by tool calls
* every metric data point
* every custom span you record via `telemetry.startActiveSpan`

## Session start

Implicit. Created when you construct the `TelemetryManager`:

```ts theme={null}
const telemetry = instrumentServer(server, telemetryConfig)
// ↑ session begins here
```

## Session duration

When you call `telemetry.shutdown()`, the package records a histogram:

| Metric                        | Unit    | Tag              |
| ----------------------------- | ------- | ---------------- |
| `mcp.server.session.duration` | seconds | `mcp.session.id` |

Wire it up to your process exit:

```ts theme={null}
const exit = async (code = 0) => {
  await telemetry.shutdown()
  process.exit(code)
}

process.on('SIGINT', () => exit(0))
process.on('SIGTERM', () => exit(0))
process.on('uncaughtException', () => exit(1))
```

<Warning>
  Skipping `shutdown()` means the final batch of metrics never leaves your
  process — including `session.duration`. Always wire it.
</Warning>

## What "session" doesn't mean

* It's **not** a per-client session. If two MCP clients connect to the same
  server process, they share one `mcp.session.id`. Use `mcp.request.id` for
  per-call correlation, and `client.address` to differentiate.
* It's **not** a transport-level connection. A stdio server has one logical
  client; an HTTP server may have many.

## Per-call ids

For correlating logs to a single tool call:

| Attribute        | Where it comes from                              |
| ---------------- | ------------------------------------------------ |
| `mcp.request.id` | UUID generated for each `tools/call` invocation. |
| `mcp.session.id` | UUID per process.                                |
| `mcp.tool.name`  | Tool that was called.                            |

Combine `(mcp.session.id, mcp.request.id)` for unique-per-call identity.