---
title: "Stage a reply attachment and return a short-lived upload URL; the file is not usable until confirmed"
method: POST
path: "/workspaces/{workspaceId}/inbox/{conversationId}/attachments/presign"
tags: ["Inbox"]
---

# Stage a reply attachment and return a short-lived upload URL; the file is not usable until confirmed

`POST /workspaces/{workspaceId}/inbox/{conversationId}/attachments/presign`

## Request

- Base URL: `https://app.communicate.so/api/v1`
- URL: `https://app.communicate.so/api/v1/workspaces/{workspaceId}/inbox/{conversationId}/attachments/presign`
- Auth: one of:
  - HTTP bearer
  - API key in cookie `__Secure-better-auth.session_token`
  - API key in cookie `better-auth.session_token`

Use an explicitly scoped user-bound account bearer credential or an application session. Scope grants are intersected with live membership, role, tenant isolation, agent access and plan limits; a credential does not grant an owner role. Invitation acceptance requires the verified recipient email.

## Path parameters

- `workspaceId` string, required
- `conversationId` string, required

## Request body

- PresignInboxAttachmentRequest
  - `filename` string, required
  - `contentType` string, required
  - `sizeBytes` integer

## Response `200`

Stage a reply attachment and return a short-lived upload URL; the file is not usable until confirmed

- PresignInboxAttachmentResponse
  - `attachmentId` string, required
  - `putUrl` string, uri, required
  - `key` string, required
  - `headers` object, required
    - `Content-Type` string, required

## Other responses

- `400`: Invalid request, timezone, resource association or confirmation.
- `401`: Missing, invalid, expired or revoked account credential or application session.
- `403`: Required account scope, live verified identity, membership or role permission is missing.
- `404`: Workspace or addressed resource is not visible to this member.
- `500`: Unexpected server failure.
- `503`: Authorization service temporarily unavailable.

---

[API](https://skmtc.dev/communicate/apis/communicate-public-rest-api-2.md) · [All operations](https://skmtc.dev/communicate/apis/communicate-public-rest-api-2/llms.txt) · [OpenAPI document](https://skmtc.dev/communicate/apis/communicate-public-rest-api-2/revisions/db6be3d36733?raw)