LTX 2 Fast: Text-to-Video AI with 4K Motion & Sound Sync
ltx/ltx-2/fast/text-to-video
Generate instant video previews with LTX 2 Fast—optimized for speed, low latency, and fast text-to-video generation.
Table of contents
1. Get started
Use RunComfy's API to run ltx/ltx-2/fast/text-to-video. For accepted inputs and outputs, see the model's schema.
curl --request POST \
--url https://model-api.runcomfy.net/v1/models/ltx/ltx-2/fast/text-to-video \
--header "Content-Type: application/json" \
--header "Authorization: Bearer <token>" \
--data '{
"prompt": "A photorealistic portrait of a stylish young woman sitting at an outdoor Parisian café with red woven bistro chairs and circular white tables. She has long, smooth, straight, honey-blonde hair, parted neatly in the middle. She is wearing a classic black beret, a crisp white button-up shirt, and a dark blue tie with diagonal gold stripes. Over her shirt, she wears a slightly oversized black leather jacket. She accessorizes with pearl and gold hoop earrings on one ear. Her makeup features sharp, winged eyeliner, defined eyebrows, and a natural nude lip color, giving her a chic, confident look. The scene captures a soft afternoon ambient light, with clear reflections on the glass window behind her. Through the window, vintage-style golden lettering that reads \"ROYH...\" is visible, partially cut off due to her posture. In the background, a Parisian street is subtly mirrored in the glass. The camera angle is eye-level, front-facing and slightly to the right, creating a natural, elegant composition. The color palette is warm and clean with a touch of Parisian café ambience. Extremely detailed, 8k resolution, sharp focus, shallow depth of field, photorealistic style, natural lighting, cinematic atmosphere, high fashion editorial aesthetic."
}'2. Authentication
Set the YOUR_API_TOKEN environment variable with your API key (manage keys in your Profile) and include it on every request as a Bearer token via the Authorization header: Authorization: Bearer $YOUR_API_TOKEN.
3. API reference
Submit a request
Submit an asynchronous generation job and immediately receive a request_id plus URLs to check status, fetch results, and cancel.
curl --request POST \
--url https://model-api.runcomfy.net/v1/models/ltx/ltx-2/fast/text-to-video \
--header "Content-Type: application/json" \
--header "Authorization: Bearer <token>" \
--data '{
"prompt": "A photorealistic portrait of a stylish young woman sitting at an outdoor Parisian café with red woven bistro chairs and circular white tables. She has long, smooth, straight, honey-blonde hair, parted neatly in the middle. She is wearing a classic black beret, a crisp white button-up shirt, and a dark blue tie with diagonal gold stripes. Over her shirt, she wears a slightly oversized black leather jacket. She accessorizes with pearl and gold hoop earrings on one ear. Her makeup features sharp, winged eyeliner, defined eyebrows, and a natural nude lip color, giving her a chic, confident look. The scene captures a soft afternoon ambient light, with clear reflections on the glass window behind her. Through the window, vintage-style golden lettering that reads \"ROYH...\" is visible, partially cut off due to her posture. In the background, a Parisian street is subtly mirrored in the glass. The camera angle is eye-level, front-facing and slightly to the right, creating a natural, elegant composition. The color palette is warm and clean with a touch of Parisian café ambience. Extremely detailed, 8k resolution, sharp focus, shallow depth of field, photorealistic style, natural lighting, cinematic atmosphere, high fashion editorial aesthetic."
}'Monitor request status
Fetch the current state for a request_id ("in_queue", "in_progress", "completed", or "cancelled").
curl --request GET \
--url https://model-api.runcomfy.net/v1/requests/{request_id}/status \
--header "Authorization: Bearer <token>"Retrieve request results
Retrieve the final outputs and metadata for the given request_id; if the job is not complete, the response returns the current state so you can continue polling.
curl --request GET \
--url https://model-api.runcomfy.net/v1/requests/{request_id}/result \
--header "Authorization: Bearer <token>"Cancel a request
Cancel a queued job by request_id, in-progress jobs cannot be cancelled.
curl --request POST \
--url https://model-api.runcomfy.net/v1/requests/{request_id}/cancel \
--header "Authorization: Bearer <token>"4. File inputs
Hosted file (URL)
Provide a publicly reachable HTTPS URL. Ensure the host allows server‑side fetches (no login/cookies required) and isn't rate‑limited or blocking bots. Recommended limits: images ≤ 50 MB (~4K), videos ≤ 100 MB (~2–5 min @ 720p). Prefer stable or pre‑signed URLs for private assets.
5. Schema
Input schema
{
"type": "object",
"title": "Input",
"required": [
"prompt"
],
"properties": {
"prompt": {
"title": "Prompt",
"description": "The textual description used to generate the video.",
"type": "string",
"default": "A photorealistic portrait of a stylish young woman sitting at an outdoor Parisian café with red woven bistro chairs and circular white tables. She has long, smooth, straight, honey-blonde hair, parted neatly in the middle. She is wearing a classic black beret, a crisp white button-up shirt, and a dark blue tie with diagonal gold stripes. Over her shirt, she wears a slightly oversized black leather jacket. She accessorizes with pearl and gold hoop earrings on one ear. Her makeup features sharp, winged eyeliner, defined eyebrows, and a natural nude lip color, giving her a chic, confident look. The scene captures a soft afternoon ambient light, with clear reflections on the glass window behind her. Through the window, vintage-style golden lettering that reads \"ROYH...\" is visible, partially cut off due to her posture. In the background, a Parisian street is subtly mirrored in the glass. The camera angle is eye-level, front-facing and slightly to the right, creating a natural, elegant composition. The color palette is warm and clean with a touch of Parisian café ambience. Extremely detailed, 8k resolution, sharp focus, shallow depth of field, photorealistic style, natural lighting, cinematic atmosphere, high fashion editorial aesthetic."
},
"duration": {
"title": "Duration",
"description": "",
"type": "integer",
"enum": [
6,
8,
10,
12,
14,
16,
18,
20
],
"default": 6
},
"resolution": {
"title": "Resolution",
"description": "The resolution of the generated video.",
"type": "string",
"enum": [
"1080p",
"1440p",
"2160p"
],
"default": "1080p"
},
"aspect_ratio": {
"title": "Aspect Ratio (W:H)",
"description": "The aspect ratio of the generated video.",
"type": "string",
"enum": [
"16:9"
],
"default": "16:9"
},
"fps": {
"title": "Frames Per Second",
"description": "Frames per second of the generated video.",
"type": "integer",
"enum": [
25,
50
],
"default": 25
},
"generate_audio": {
"title": "Generate Audio",
"description": "Whether to generate audio for the generated video.",
"type": "boolean",
"default": true
}
}
}Output schema
{
"output": {
"type": "object",
"properties": {
"image": {
"type": "string",
"format": "uri",
"description": "single image URL"
},
"video": {
"type": "string",
"format": "uri",
"description": "single video URL"
},
"images": {
"type": "array",
"description": "multiple image URLs",
"items": { "type": "string", "format": "uri" }
},
"videos": {
"type": "array",
"description": "multiple video URLs",
"items": { "type": "string", "format": "uri" }
}
}
}
}Video Models/Tools
Image Models
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