FLUX.1 Kontext [dev] API Reference

Request body

Submit an async generation request. The model field selects the model; other fields are model-specific input parameters.

stringmodelrequired

Model identifier. Set to bfl/flux-2/kontext/dev.

Default: bfl/flux-2/kontext/dev

stringpromptrequired

The prompt to edit the image.

stringimagerequired

The URL of the image to edit. Max width: 14142px, Max height: 14142px, Timeout: 20s

Optional<number>guidance_scale

The CFG (Classifier Free Guidance) scale is a measure of how close you want the model to stick to your prompt when looking for a related image to show you.

Range: 1 to 20

Default: 2.5

Optional<integer>num_inference_steps

The number of inference steps to perform.

Range: 10 to 50

Default: 28

Optional<string>output_format

Output format

Allowed values: jpeg, png

Default: jpeg

Optional<string>resolution_mode

Determines how the output resolution is set for image editing. - `auto`: The model selects an optimal resolution from a predefined set that best matches the input image's aspect ratio. This is the recommended setting for most use cases as it's what the model was trained on. - `match_input`: The model will attempt to use the same resolution as the input image. The resolution will be adjusted to be compatible with the model's requirements (e.g. dimensions must be multiples of 16 and within supported limits). Apart from these, a few aspect ratios are also supported.

Allowed values: auto, match_input, 1:1, 16:9, 21:9, 3:2, 2:3, 4:5, 5:4, 3:4, 4:3, 9:16, 9:21

Default: match_input

Optional<integer>seed

The same seed and the same prompt given to the same version of the model will output the same image every time.

Response Schema

The submit endpoint returns a run response. If its status is pending or running, poll GET /v1/run/{id} with the returned opaque ID until it reaches a terminal state.

stringidrequired

Opaque SandBase run identifier. Use it exactly as returned; no prefix is guaranteed.

stringstatusrequired

Current public run status.

Allowed values: pending, running, completed, failed, timeout

Optional<string>model

Public SandBase model name used for this run.

Optional<array<object>>outputs

Present only for completed runs. Each object is capability-specific; inspect the selected model schema for its fields.

Optional<object>error

Present only for failed or timeout runs. Contains a public error type and sanitized message.

Optional<string>error.type

Stable public error category.

Optional<string>error.message

Sanitized error message safe to show to clients.

Optional<object>usage

Usage details when available.

Model capabilities

array<string>capability_tagsrequired

Capabilities declared by the model registry.

Default: image-to-image

stringexecution_moderequired

Execution mode declared by the model registry.

Default: async

# 1. Submit a generation request curl -X POST https://api.sandbase.ai/v1/run \ -H "Authorization: Bearer $SANDBASE_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "model": "bfl/flux-2/kontext/dev", "prompt": "Change the setting to a day time, add a lot of people walking the sidewalk while maintaining the same style of the painting", "image": "https://static.sandbase.ai/examples/bfl/flux-2/kontext/dev/input_image_0.webp", "output_format": "jpeg" }' # 2. If the response is still running, poll the returned id curl https://api.sandbase.ai/v1/run/f3d2e8a1-7c4b-4a12-9d2e-123456789abc \ -H "Authorization: Bearer $SANDBASE_API_KEY"