> ## 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 |