---
title: "Upload attachments"
method: POST
path: "/api/v0/agent/sessions/{session_id}/attachments"
tags: ["Agent Attachments"]
---

# Upload attachments

`POST /api/v0/agent/sessions/{session_id}/attachments`

Upload image files to attach to the next agent message. Max 8 files, 20MB each.

## Path parameters

- `session_id` string, uuid, required

## Response `200`

Successful Response

- AttachmentUploadResponse[]
  - `attachment_id` string, uuid, required — Public ID of the attachment.
  - `filename` string, required — Original filename.
  - `content_type` string, required — MIME type of the stored image, which may differ from the uploaded one: formats the vision models reject (BMP, GIF) are stored as PNG.
  - `size_bytes` integer, required — Size of the stored file in bytes.

## Other responses

- `422` — Validation Error

---

[API](https://skmtc.dev/outerport/apis/outerport-api.md) · [All operations](https://skmtc.dev/outerport/apis/outerport-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/outerport/outerport-api/revisions/f565b46daaea/schema)