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

# SessionCostMeta

## Fields

| Field             | Type                                                                          | Required             | Description                                                                                    | Example                  |
| ----------------- | ----------------------------------------------------------------------------- | -------------------- | ---------------------------------------------------------------------------------------------- | ------------------------ |
| `as_of`           | *str*                                                                         | :heavy\_check\_mark: | ISO-8601 timestamp when the response was generated.                                            | 2026-05-12T02:00:00.000Z |
| `version`         | [components.SessionCostMetaVersion](../components/sessioncostmetaversion.mdx) | :heavy\_check\_mark: | Dataset version.                                                                               |                          |
| `window_days`     | *Nullable\[int]*                                                              | :heavy\_check\_mark: | Number of days in the weekly session sample window, or null when no snapshot is published.     | 30                       |
| `window_end_date` | *Nullable\[str]*                                                              | :heavy\_check\_mark: | UTC date of the final day in the session sample window, or null when no snapshot is published. | 2026-05-11               |