# Seedance 2.5 (video)

> Seedance 2.5 makes cinematic clips of 4 to 30 seconds with synchronized audio from text, a first frame, or a mix of image, video and audio references. It is best at multi-beat storytelling, dialogue with lip-sync, and product motion in one long take.

Status: roasOS API v1.1. Catalog `model-catalog@2026-10-06.v5`, pricing `customer-pricing@2026-11-05.v15`. The endpoint `POST /v1/video/seedance-2.5` is live. `POST /v1/generations` stays for one minor version as a deprecated alias (see "Today").

## Endpoint
POST https://api.roasos.com/v1/video/seedance-2.5
Auth: Authorization: Bearer roasos_sk_… (scope api:write). Idempotency-Key required. quote_only / quote_id / webhook_url as in https://docs.roasos.com/llms.txt.

## Good at
Seedance 2.5 is the premium video model of the roster. It makes one continuous take of up to 30 seconds with sound effects, ambience and lip-synced speech; the audio has no surcharge. It follows beat-by-beat prompts with timestamps, and it keeps a product, a set and a palette stable across cuts. Reference mode binds images, videos and audio files to ordinal tags, so a caller can lock a product look, copy a motion, or use a voice track. It accepts a human face in a reference image, a real photo or a saved avatar. roasOS runs this model on a provider route that accepts faces.

## Pricing
Unit: clip. Pricing key: `seedance-2.5`.

| request | credits |
|---|---|
| `4s_720p` | 12 |
| `12s_720p` | 36 |
| `30s_720p` | 90 |
| `4s_720p_no_audio` | 12 |

Credits come from the roasOS pricing table (`MODEL_COSTS`) through the catalog. No other field changes the price.

## Modes
- `text-to-video`
- `image-to-video`
- `reference-to-video`

The worker derives the mode from the media fields of the request.
Provider endpoints: `bytedance/seedance-2.5/image-to-video` · `bytedance/seedance-2.5/reference-to-video` · `bytedance/seedance-2.5/text-to-video`.

## Request fields
| field | type | required | default | rule |
|---|---|---|---|---|
| `aspect_ratio` | enum | no | `16:9` | `auto`, `9:16`, `1:1`, `3:4`, `4:3`, `16:9`, `21:9`; only in `text-to-video`, `reference-to-video` |
| `audio_urls` | string[] | no | — | ≤ 10 items; only in `reference-to-video` |
| `avatar_id` | string | no | — | UUID; only in `reference-to-video` |
| `avatar_outfit` | string | no | — | ≤ 500 characters |
| `duration_seconds` | enum | no | `5` | `auto`, `4`, `5`, `6`, `8`, `10`, `12`, `15`, `20`, `25`, `30`; required in `reference-to-video` |
| `end_image_url` | string | no | — | https URL; ≤ 4,096 characters; only in `image-to-video` |
| `extend_of_generation_id` | string | no | — | UUID |
| `generate_audio` | boolean | no | `true` | — |
| `image_url` | string | no | — | https URL; ≤ 4,096 characters; only in `image-to-video` |
| `mode` | enum | no | — | `text-to-video`, `image-to-video`, `reference-to-video` |
| `prompt` | string | yes | — | ≥ 1 character; ≤ 10,000 characters |
| `quote_id` | string | no | — | UUID |
| `quote_only` | boolean | no | `false` | — |
| `references` | string[] | no | — | ≤ 30 items; only in `reference-to-video` |
| `resolution` | enum | no | `720p` | `480p`, `720p`, `1080p` |
| `scene_id` | string | no | — | UUID |
| `video_urls` | string[] | no | — | ≤ 10 items; only in `reference-to-video` |
| `wait_timeout_seconds` | integer | no | `0` | 0–60 |
| `webhook_url` | string | no | — | https URL; ≤ 4,096 characters |

The schema is strict: a field that is not in this table returns `400 unsupported_option`. Field names are the roasOS role names, one name per role across every family.

## Media
- `avatar_id` — identity; the saved character reference sheet, with a derived portrait only where the model requires a single face or source frame
- `references` — style and appearance references
- `image_url` — first frame (or the single source image)
- `end_image_url` — last frame
- `scene_id` — first frame — a scene this workspace owns
- `video_urls` — reference videos
- `audio_urls` — reference or driving audio

| role | items | max size | content types | duration |
|---|---|---|---|---|
| `audio_urls` | ≤ 10 | 14.3 MB | `audio/mpeg`, `audio/wav` | 1.8–30.2 s |
| `end_image_url` | ≤ 1 | 10 MB | `image/jpeg`, `image/png`, `image/webp` | — |
| `image_url` | ≤ 1 | 10 MB | `image/jpeg`, `image/png`, `image/webp` | — |
| `references` | ≤ 30 | 10 MB | `image/jpeg`, `image/png`, `image/webp` | — |
| `video_urls` | ≤ 10 | 100 MB | `video/mp4` | 2–30 s |

- Refused: `elements`, `product_id`, `product_images`, `reference_images`, `scene_image`, `video_url`, `audio_url`, `voice_id`. A refused role returns `400 unsupported_option`.
- Every URL must be an immutable object on `https://cdn.roasos.com/…` that your workspace owns; any other URL is `400 reference_media_not_workspace_owned`. Upload with `POST /v1/uploads` (direct POST of the bytes to `put_url`, or a `source_url` import), then use the returned CDN URL.

## Prompt
Limit 10,000 characters including the roasOS route-facts block (`ROUTE-VERIFIED FEATURE FACTS:` with one line for the first frame or the references). Tags: `@Image1`, `@Video1`, `@Audio1`, each once, in order.
- Order: Subject → Action → Camera → Style/lighting → Constraints. One primary movement per beat.
- Give each beat a start time: `[00:00] … [00:05] …`.
- Write dialogue as `She says: "…"` with the delivery; name the mic source ("direct phone mic, room ambience, no music").
- Dialogue pacing: 1–8 words ≈ 4–5 s, 9–15 ≈ 6–8 s, 16–25 ≈ 9–12 s, 26–35 ≈ 13–15 s.
- Avoid: cinematic, professional, stunning, 8k, studio, perfect. Say "documentary", "handheld", "phone-shot".
- Motion needs intensity and degree adverbs ("slowly picks up the bottle with her right hand and turns the label to camera").
- Lock a product: "The product from @Image2 must remain visually unchanged in every shot".
- A face in an image reference is accepted. An `avatar_id` appends the avatar's front and full-body shots as the trailing `@ImageN` entries.
- If the provider refuses a face, the run fails with `provider_rejects_face_references`. roasOS refunds the reservation.

## Not exposed
- `duration_seconds`: values not exposed — `7`, `9`, `11`, `13`, `14`, `16`, `17`, `18`, `19`, `21`, `22`, `23`, `24`, `26`, `27`, `28`, `29`.
- `video_urls`: values not exposed — `MOV containers`.
- `references`: values not exposed — `BMP`, `TIFF`, `GIF`, `HEIC`, `HEIF`.
- `seed`: pinned to `output only`.
- `end_user_id`: not accepted by this public endpoint.

## Result
Result kind `video`. Always present: `url`.
```json
{ "data": { "id": "gen_…", "kind": "video", "model": "seedance-2.5", "status": "completed", "result": {"url":"https://cdn.roasos.com/workspaces/ws_01/result"} } }
```
Files live on `https://cdn.roasos.com` and are immutable; a result URL can be a media input to the next call. Poll `GET /v1/jobs/{id}/status` → `{ id, status, updated_at }`, then `GET /v1/jobs/{id}/result` (`409 run_not_completed` until the job is `completed`, `failed` or `canceled`). Statuses: `queued → processing → completed | failed | canceled`.

## Example
```bash
# 1. quote — nothing is spent
curl -X POST https://api.roasos.com/v1/video/seedance-2.5 \
  -H "Authorization: Bearer roasos_sk_live_…" \
  -H "Idempotency-Key: 0f1c9e2a-seedance-2.5-0001" \
  -H "Content-Type: application/json" \
  -d '{"quote_only":true,"prompt":"A woman holds the bottle at eye level in a bright kitchen, morning light, static camera."}'
# → 200 { "data": { "kind": "quote", "quote_id": "q_7Hk…", "credits": 12, "expires_at": "…", "confirmation": { "model": "seedance-2.5", "example": "4s_720p" } } }

# 2. run — the same body and the same Idempotency-Key, quote_id instead of quote_only
curl -X POST https://api.roasos.com/v1/video/seedance-2.5 \
  -H "Authorization: Bearer roasos_sk_live_…" \
  -H "Idempotency-Key: 0f1c9e2a-seedance-2.5-0001" \
  -H "Content-Type: application/json" \
  -d '{"quote_id":"q_7Hk…","prompt":"A woman holds the bottle at eye level in a bright kitchen, morning light, static camera."}'
# → 201 { "data": { "id": "gen_…", "kind": "video", "model": "seedance-2.5", "status": "queued", "credits_reserved": 12, "links": { "status": "/v1/jobs/gen_…/status", "result": "/v1/jobs/gen_…/result" } } }

# 3. poll
curl https://api.roasos.com/v1/jobs/gen_…/status -H "Authorization: Bearer roasos_sk_live_…"
curl https://api.roasos.com/v1/jobs/gen_…/result -H "Authorization: Bearer roasos_sk_live_…"
```

## Today
`POST /v1/generations { "type": "video", "model": "seedance-2.5", "options": { prompt, image, last_frame, reference_images, reference_videos, audio_urls, duration, resolution, aspect_ratio, generate_audio } }`. Contract authority `exact` for all three modes. It returns the same job envelope. The alias stays one minor version after v1.1 ships.

## See also
https://docs.roasos.com/models/video/seedance-2.5 · https://api.roasos.com/v1/catalog/video/seedance-2.5 · bytedance/seedance-2.5/image-to-video · bytedance/seedance-2.5/reference-to-video · bytedance/seedance-2.5/text-to-video