bfl/flux-2/flex
Flux 2 Flex is BFL's advanced text-to-image AI model. Create photorealistic images, illustrations, and concept art from natural language descriptions with exceptional detail and prompt adherence.
Example output — click Run to generate your own
Send your first request
OpenAI-compatible endpoint with unified authentication and usage tracking.
https://api.sandbase.ai/v1/runbfl/flux-2/flexInput Schema
6 parameters · 1 required · 5 optional
| Parameter | Type | Required | Description |
|---|---|---|---|
prompt | string | Required | The prompt to generate an image from. |
seed | integer | Optional | The seed to use for the generation. |
aspect_ratio | string | Optional | The aspect ratio of the generated image. · Options: 21:9, 16:9, 3:2, 4:3, 5:4, 1:1, 4:5, 3:4, 2:3, 9:16 · Default: "16:9" 21:916:93:24:35:41:14:53:42:39:16 |
output_format | string | Optional | The format of the generated image. · Options: jpeg, png · Default: "jpeg" jpegpng |
guidance_scale | number | Optional | The guidance scale to use for the generation. · Min: 1.5 · Max: 10 · Default: 3.5 |
num_inference_steps | integer | Optional | The number of inference steps to perform. · Min: 2 · Max: 50 · Default: 28 |
Output Schema
| Field | Type | Description |
|---|---|---|
id | string | Unique identifier for the generation task |
status | string | Task status: pending, running, completed, failed, timeout |
model | string | Model used for the generation |
outputs | array | Array of output items |
outputs[].url | string | URL of the generated artifact |
outputs[].content_type | string | MIME type (e.g. image/png, video/mp4) |
error | object | null | Error details if failed, null on success |
error.type | string | Machine-readable error type code |
error.message | string | Human-readable error description |
Async Workflow
This model uses asynchronous execution. Submit a request and poll for the result.
- Submit — POST to /v1/run, receive an
id - Poll — GET /v1/run/{id} until status is
completed,failed, ortimeout - Retrieve — Read
outputsfrom the completed response
Code Examples
Ready-to-run snippets
# Step 1: Submit
curl -X POST https://api.sandbase.ai/v1/run \
-H "Content-Type: application/json" \
-H "Authorization: Bearer YOUR_API_KEY" \
-d '{
"model": "bfl/flux-2/flex",
"prompt": "A high-quality 3D render of a cute fluffy monster eating a giant donut; the fur simulation is incredibly detailed, the donut glaze is sticky and reflective, bright daylight lighting, shallow depth of field.",
"aspect_ratio": "16:9",
"output_format": "jpeg",
"guidance_scale": 3.5,
"num_inference_steps": 28
}'
# Step 2: Poll result (replace <id>)
curl https://api.sandbase.ai/v1/run/<id> \
-H "Authorization: Bearer YOUR_API_KEY"API README
Flux 2 Flex
Flux 2 Flex is FLUX.2 Flex’s image generation route, specialized for typography, fine details, and deliberate visual control. It builds text-heavy and detail-sensitive layouts from a precise written brief.
Use Flex for posters, packaging, labels, editorial layouts, interface-like graphics, and product visuals where wording and small visual elements matter. Provide exact wording, hierarchy, placement, color, material, and composition. The route rewards explicit art direction rather than vague style keywords.
Highlights
- Advanced text rendering. Creates readable wording inside posters, labels, packaging, and editorial compositions.
- Fine-detail preservation. Maintains small graphic elements, textures, edges, and precise visual features.
- Exact color direction. Responds to explicit color values and controlled palette requirements.
- Layout-sensitive generation. Coordinates typography, hierarchy, spacing, and imagery within designed assets.
Pricing
| Output size | Billing unit | Price |
|---|---|---|
| First started megapixel | Per request | $0.050 |
| Each additional started megapixel | Per megapixel | $0.050 |
When to Use
| ✅ Good fit | ❌ Consider alternatives |
|---|---|
| The project needs this exact generation or editing route | The intended task belongs to video, audio, or 3D media |
| Available references match every required local field | Required source assets or rights are unavailable |
| The brief can specify composition, color, and finish | Output must be deterministic at pixel level |
| Supported dimensions and formats fit final placement | Delivery requires unsupported canvas specifications |
| An asynchronous generated image fits production | A live frame-synchronous response is mandatory |
Prompt Guide
Write a complete visual brief: identify the subject and references, define composition and viewpoint, describe lighting, palette, materials, typography, and finish, then list exact preservation constraints. FLUX.2 Klein does not rely on prompt upsampling, so use clear descriptive sentences rather than sparse keywords.
{
"prompt": "A photorealistic editorial composition with precise subject placement, controlled lighting, exact colors, and clean typography",
"seed": 1,
"aspect_ratio": "21:9",
"output_format": "jpeg"
}
Technical Specs
| Spec | Value |
|---|---|
| Model ID | bfl/flux-2/flex |
| Input fields | seed (integer)<br>prompt (string)<br>aspect_ratio (string; 21:9, 16:9, 3:2, 4:3, 5:4, 1:1, 4:5, 3:4, 2:3, 9:16)<br>output_format (string; jpeg, png)<br>guidance_scale (number; 1.5–10)<br>num_inference_steps (integer; 2–50) |
| Required input | prompt |
| Output fields | url, content_type |
| Execution | Asynchronous job |
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