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

# Start creative session

> Generate a reviewable creative draft gallery for a campaign

`POST /api/v2/buyer/campaigns/{campaignId}/creative-sessions`

Starts a reviewable creative session and returns draft variants for the campaign.
Use the session to compare directions, refine one, evaluate it, and finalize the
approved output as a campaign Creative.

## Request

| Field | Type | Required | Notes |
| - | - | - | - |
| `storefrontId` | number | No | Connected creative-provider storefront when the engine requires one. Omit it for a buyer-provided model key. |
| `providerType` | string | Yes | Creative provider to use. |
| `request` | object | Yes | Provider-neutral creative request, including the brief and target format when needed. |
| `prompt` | string | No | Buyer-facing creative direction. |
| `language` | string | No | Supported BCP-47 language for generated audio: English, Dutch, Spanish, or Portuguese, such as `es` or `pt-BR`. Omit it to preserve the existing language selection. |

For an AudioStack session, set `language` when the buyer specifies the spoken
language. It generates the script and AudioStack speech in that language; it
is not a translation request for other creative modalities.

```json theme={null}
{
  "storefrontId": 1725,
  "providerType": "audiostack",
  "language": "pt-BR",
  "prompt": "Create a 30-second audio ad for the new collection.",
  "request": {
    "format_kind": "audio_hosted",
    "params": { "duration_ms_exact": 30000 },
    "creative_brief": {
      "prompt": "A warm introduction to the new collection."
    }
  }
}
```

Returns `201 Created` with the creative session, including its draft variants
and creative plan.


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