Seedance 2.0 Fast

Endpoint

POST https://api.roasos.com/v1/video/seedance-2

Send your API key as a bearer token. The key needs the scope api:write. Every paid request also needs an Idempotency-Key header.

The envelope fields quote_only, quote_id, webhook_url and wait_timeout_seconds behave the same on each model endpoint. Refer to Jobs and Quotes and credits.

Good at

Seedance 2.0 Fast makes one continuous take of up to 15 seconds with sound effects, ambience and lip-synced speech; the audio has no surcharge. It does multi-shot editing and director-level camera control inside one clip, so a beat-by-beat prompt gets cuts. Use it for drafts and for volume, where latency and price matter more than the highest fidelity. Reference mode binds images, videos and audio files to ordinal tags. It does not accept a human face in a reference image, and it takes no avatar_id; use Kling 4.0 elements for a locked identity.

Pricing

The unit is one clip. Pricing key: seedance-2.

The credits come from the roasOS pricing table. No other field changes the price. To get the exact price of your request, send it with quote_only: true first.

Modes

• text-to-video
• image-to-video
• reference-to-video

roasOS selects the mode from the media fields of your request. You do not send a mode.

Provider endpoints: bytedance/seedance-2.0/fast/image-to-video · bytedance/seedance-2.0/fast/reference-to-video · bytedance/seedance-2.0/fast/text-to-video.

Request fields

The schema is strict. A field that is not in this table gets 400 unsupported_option. The field names are the roasOS role names. One role has one name in every family.

Media

This endpoint accepts these media roles:

• 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

Every other role is refused: avatar_id, elements, product_id, product_images, reference_images, scene_image, video_url, audio_url, voice_id. A refused role gets 400 unsupported_option.

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.

• Write the prompt as one continuous progression with plain cause-and-effect motion.
• Order: Subject → Action → Camera → Style/lighting → Constraints. One primary movement per beat.
• Give each beat a start time: [00:00] … [00:05] ….
• Put quoted dialogue in the prompt when you want speech: She says: "…". Name the mic source.
• Dialogue pacing: 1–8 words ≈ 4–5 s, 9–15 ≈ 6–8 s, 16–25 ≈ 9–12 s.
• Avoid: cinematic, professional, stunning, 8k, studio, perfect.
• Do not put a face in an image reference; describe the person in words.

Not exposed

These catalog entries describe omitted inputs, pinned values and source constraints. They do not imply that the provider accepts every listed field.

• bitrate_mode — pinned to text-to-video and image-to-video; the field is sent on the reference lane only.
• aspect_ratio — pinned to auto.
• end_user_id — not accepted by this public endpoint.
• video_urls — these values are not available: MOV containers.
• references — these values are not available: BMP, TIFF, GIF, HEIC, HEIF.
• avatar_id — not accepted by this public endpoint.
• product_id — not accepted by this public endpoint.
• seed — pinned to output only.
• negative_prompt — not accepted by this public endpoint.

Result

The result kind is video. Always present: url.

{
  "data": {
    "id": "gen_…",
    "kind": "video",
    "model": "seedance-2",
    "status": "completed",
    "result": {
      "url": "https://cdn.roasos.com/workspaces/ws_01/result"
    }
  }
}

The files are immutable objects on https://cdn.roasos.com. A result URL is a valid media input for your next request.

Example

The three steps are always the same: quote, run, poll.

# 1. Quote. Nothing is spent.
curl -X POST https://api.roasos.com/v1/video/seedance-2 \
  -H "Authorization: Bearer roasos_sk_live_..." \
  -H "Idempotency-Key: 0f1c9e2a-seedance-2-0001" \
  -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", "example": "4s_720p" } } }

# 2. Run. Same body, same Idempotency-Key, quote_id in place of quote_only.
curl -X POST https://api.roasos.com/v1/video/seedance-2 \
  -H "Authorization: Bearer roasos_sk_live_..." \
  -H "Idempotency-Key: 0f1c9e2a-seedance-2-0001" \
  -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_...", "status": "queued", "credits_reserved": 12 } }

# 3. Poll, then read the result.
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_..."

The deprecated path

POST /v1/generations still reaches this model for one minor version. It is deprecated. This is how it maps:

POST /v1/generations { "type": "video", "model": "seedance-2", "options": { prompt, image, last_frame, reference_images, reference_videos, audio_urls, duration, resolution, aspect_ratio, generate_audio } }. Contract authority exact. Write every ordinal tag yourself: a missing @Image1, @Video1 or @Audio1 is a 400 on both surfaces. The alias stays one minor version after v1.1 ships.

See also

• llms.txt for this model — the same facts as one plain-text file for an agent.
• GET https://api.roasos.com/v1/catalog/seedance-2 — the machine-readable form: enums, defaults, limits and prices. Refer to the API reference.
• Jobs — how to poll a job and read its result.
• Provider endpoints: bytedance/seedance-2.0/fast/image-to-video · bytedance/seedance-2.0/fast/reference-to-video · bytedance/seedance-2.0/fast/text-to-video.