# Session State Producer

The `session-state-producer` tracks history for identities published by the
`agent-identity` request-header plugin and publishes per-request session state
for scheduling plugins through the request attribute store.

The producer uses only the `agent-identity` attribute. `SessionIDDataKey` is a
separate attribute produced by `session-id-producer` from one configured header
or cookie for general session-affinity use.

## Configuration

Both plugins must be enabled, and Alpha plugins must be allowed by the EPP
process. `agent-identity` is a required data dependency, so configuration
loading fails if no plugin declares that it produces the agent identity
attribute.

```yaml
plugins:
- type: agent-identity
- type: session-state-producer
  parameters:
    evictionTtlSeconds: 3600
    evictionSweepSeconds: 300
```

| Parameter | Default | Description |
|---|---:|---|
| `evictionTtlSeconds` | `3600` | Maximum session idle time before its state is removed. Set to `0` to disable eviction. |
| `evictionSweepSeconds` | `300` | Interval between idle-state scans. Must be greater than `0`. |

## Produced data

The producer writes `SessionStateDataKey` with a `sessionstate.SessionState`
value:

- `TurnsTaken`: requests dispatched before the current request.
- `Duration`: elapsed time since the session was first observed.
- `LastSeenAt`: time the preceding request was observed; for a new session it
  is the current request time.
- `InFlightRequests`: requests dispatched by EPP whose response lifecycle has
  not ended.
- `CompletedRequests`: requests whose responses ended naturally. A complete
  model error response is a natural completion.
- `TotalInputTokens`: prompt tokens reported by naturally completed responses.
- `TotalOutputTokens`: completion tokens reported by naturally completed
  responses.

The current request is marked as seen during data production. Its turn is
counted in `PreRequest` only after scheduling selects at least one target, so
the next request observes the increment. Multiple scheduling profiles still
count as one turn. The request is also added to `InFlightRequests` at that
point and removed when its response lifecycle ends. Client disconnects,
evictions, and internal errors do not contribute to `CompletedRequests` or the
token totals because their usage may be incomplete. A naturally completed
response without usage data contributes zero tokens.

State is local to one EPP replica. Idle session state is removed according to
the configured eviction TTL and sweep interval. Sessions with in-flight
requests are retained until those requests end.