> This page is for version v2024-12-23.
> For other versions, use one of these documentation indexes:
> - v2026-02-09 (default): https://docs.extend.ai/2026-02-09/llms.txt
> - v2025-04-21: https://docs.extend.ai/2025-04-21/llms.txt
> - v2024-12-23: https://docs.extend.ai/2024-12-23/llms.txt

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.extend.ai/llms.txt
> Use this file to discover all available pages before exploring further.
>
> ## API version
> The current API version is `2026-02-09`, served at the site root (no version prefix in URLs).
> If this page URL contains `/2025-04-21/` or `/2024-12-23/`, you are reading an older API version.
> Prefer the current docs at https://docs.extend.ai/llms.txt unless the user explicitly needs that older version.
> Do not treat older-version pages as the source of truth for new integrations.

# Multifile evaluation set items

> Evaluation set items can now reference an ordered package of files via fileIds, and are evaluated as a single multifile extraction run on the 2026-02-09 API.

Evaluation sets can now hold **multifile items**, so you can measure the accuracy of an extractor that runs over a [package of files](/2026-02-09/extraction/multifile) rather than a single document.

* **`fileIds`** on `POST /evaluation_sets/{id}/items` — pass an ordered array of 2–50 unique file IDs instead of `fileId`. Exactly one of `fileId` or `fileIds` must be provided per item. Multifile items are only supported on evaluation sets attached to a JSON-schema extractor.
* **`files`** on `EvaluationSetItem` and `EvaluationSetItemSummary` — an ordered array of file summaries, populated for multifile items and `null` otherwise.
* **`file`** is now nullable — `null` for multifile items, matching the `file` / `files` convention on `ExtractRun`.

When you run the set, each multifile item is evaluated as one multifile extraction run with a single `expectedOutput` covering the whole package. See [Add a multifile item](/2026-02-09/evaluation/creating-evaluation-sets#add-a-multifile-item).