Flux 3 Video Extend

bfl/flux-3/video-extend

Flux 3 Extend Video is BFL's video-to-video AI model. Transform, enhance, and edit video content using text prompts - from style changes to object manipulation and scene modification.

Use in agent Get API key

Base price: $2.05USD / run
Execution: async
Model type: video
Input fields: 6

Production route

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Playground

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Input

Prompt(string)

The text prompt describing how the video continues from the source clip's final frames.

Aspect Ratio(string)

Output aspect ratio. Follows the input when omitted. Allowed values: 21:9, 2:1, 16:9, 4:3, 1:1, 3:4, 9:16.

Video URL(string)

URL of the input video. MP4, under 50 MB and under 15 seconds.

Resolution(string)

Resolution of the generated video. Allowed values: 720p, 1080p.

Duration(integer)

Seconds of new footage to add after the source video (5-20). Allowed values: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.

Generate Audio(boolean)

Whether to generate audio for the video.

OutputExample

Open original

Examples

Select an example to load its inputs and result into the playground.

Model card

Specifications

Pricing

Base price: $2.05 / run

Context & modalities

Input: Schema-defined
Output: video

Capabilities

Chat: Not supported
Vision: Not supported
Reasoning: Not supported
Structured output: Not supported
Function calling: Not supported
Audio input: Not supported

Access

Provider: BFL
Model ID: bfl/flux-3/video-extend
Execution: async
API: Unified Run API
Endpoint: /v1/run

API README

Flux 3 Video Extend

Flux 3 Extend Video belongs at the continuation of finished moving material stage of a visual workflow. Rather than treating the model as an isolated demonstration, teams can place it inside briefing, review, selection, and handoff practices where an existing clip becomes the narrative handoff point, allowing a sequence to grow without restarting its visual premise from the beginning. This positioning clarifies why the model earns a place in a real creative pipeline and what kind of decision it helps people make.

A practical use of Flux 3 Extend Video is longer social edits, additional beats after a product reveal, scene continuations, and narrative inserts that must follow established footage. Begin by agreeing on the creative objective and review criteria, prepare only the source material needed for that objective, and compare results against audience, brand, editorial, and production needs. Technical request choices remain documented below so the prose can stay focused on planning and creative value.

Highlights

Seamless audiovisual continuation. Carries movement, camera direction, dialogue, effects, and ambience across the join with the source clip.

Causal scene development. Predicts a plausible next event while preserving the physical and narrative logic already established.

Character and setting continuity. Maintains recognizable subjects, locations, and visual language as the sequence advances.

Synchronized sound evolution. Extends spoken performance and environmental audio together with the generated frames. FLUX 3 jointly models video and sound, grounding visual action, speech, effects, and ambience in one evolving scene.

Pricing

Option	Price
720p per second	$0.41
1080p per second	$0.53
5 seconds at 720p	$2.05

Billed per requested second of new footage. The source video is not billed.

When to Use

✅ Good fit	❌ Consider alternatives
The model's named workflow matches the source material and intended output	A different input modality or model route is required
A managed asynchronous result is suitable for the production pipeline	A synchronous, interactive editor is essential
The documented controls cover the required duration, framing, or format	The project needs controls outside this endpoint's schema
Creative iteration benefits from a repeatable request structure	Exact deterministic pixels, frames, geometry, or samples are mandatory
A finished downloadable media asset is the desired deliverable	Editable source layers or a native project file are required

Prompt Guide

For generation, state the intended result first, then add the subject or source treatment, progression, style, and delivery constraints. Keep one creative variable per phrase, use the documented field names for controls, and change one setting at a time when comparing results.

{
  "aspect_ratio": "21:9",
  "duration": 5,
  "prompt": "The camera keeps tracking as the subject turns and smiles.",
  "resolution": "720p",
  "video": "https://example.com/source.mp4"
}

Technical Specs

Spec	Value
Model ID	`bfl/flux-3/extend-video`
Inputs	aspect_ratio, duration, generate_audio, prompt, resolution, video
Required inputs	prompt
Output fields	content_type, url
Execution	Async (submit, then poll for result)
Duration	5 / 6 / 7 / 8 / 9 / 10 / 11 / 12 / 13 / 14 / 15 / 16 / 17 / 18 / 19 / 20
Resolution	720p / 1080p
Aspect Ratio	21:9 / 16:9 / 3:2 / 4:3 / 5:4 / 1:1 / 4:5 / 3:4 / 2:3 / 9:16

Related Models

bfl/flux-3/extend-video/draft — Compare this concrete local family route.
bfl/flux-3/draft-enhance — Compare this concrete local family route.
bfl/flux-3/first-last-frame-to-video — Compare this concrete local family route.

Start building

Send your first request

OpenAI-compatible endpoint with unified authentication and usage tracking.

Production API

Unified Run API endpoint

https://api.sandbase.ai/v1/run

Model ID

bfl/flux-3/video-extend

# The quoted heredoc keeps Unicode and shell metacharacters unchanged.
result=$(curl --fail-with-body --silent \
  -X POST "https://api.sandbase.ai/v1/run" \
  -H "Authorization: Bearer $SANDBASE_API_KEY" \
  -H "Content-Type: application/json" \
  --data-binary @- <<'SANDBASE_JSON'
{
  "model": "bfl/flux-3/video-extend",
  "video": "https://storage.googleapis.com/falserverless/example_inputs/flux-3-red-panda.mp4",
  "prompt": "The camera keeps tracking as the subject turns and smiles.",
  "duration": 5,
  "resolution": "720p",
  "generate_audio": true
}
SANDBASE_JSON
)
run_id=$(printf '%s' "$result" | jq -r .id)
for attempt in $(seq 1 120); do
  status=$(printf '%s' "$result" | jq -r .status)
  case "$status" in completed|failed|timeout) break ;; esac
  sleep 2
  result=$(curl --fail-with-body --silent \
    -H "Authorization: Bearer $SANDBASE_API_KEY" \
    "https://api.sandbase.ai/v1/run/$run_id")
done
status=$(printf '%s' "$result" | jq -r .status)
[ "$status" = completed ] || { echo "Generation ended: $status" >&2; exit 1; }
printf '%s\n' "$result"

Choose your model

Compare models

All image & video models

Model	Type	Default price	Released
Flux 3 Video ExtendThis model `BFL`	Video	$2.05 / run	Aug 4, 2026
Flux 3 Text to Video `BFL`	Video	$0.85 / run	Aug 4, 2026
Flux 3 Image to Video `BFL`	Video	$0.85 / run	Aug 4, 2026
Flux 3 First-Last Frame to Video `BFL`	Video	$0.85 / run	Aug 4, 2026
Flux 3 Keyframes to Video `BFL`	Video	$0.85 / run	Aug 4, 2026
Flux 3 Text to Video Draft `BFL`	Video	$0.30 / run	Aug 4, 2026

Questions

FAQ

How do I call BFL Flux 3 Video Extend through SandBase?

Create a SandBase API key, then send requests with the model ID "bfl/flux-3/video-extend" to Unified Run API (/v1/run) at https://api.sandbase.ai. The request examples on this page show the exact payload.

Do I need a separate BFL account?

No. One SandBase API key and balance gives you access to BFL Flux 3 Video Extend and the other models in the catalog; you do not need to sign up with BFL separately.