# FLUX 3 Image Klein ## Quick example Submit one image request, save the returned `id`, and poll until the task is `completed` or `failed`. This API uses asynchronous tasks and URL outputs. ```bash curl https://api.seedrouter.ai/v1/images/generations \ -H "Authorization: Bearer $SEEDROUTER_API_KEY" \ -H 'Content-Type: application/json' \ -d '{"model":"flux-3-image-klein","prompt":"An amber bottle on pale limestone in soft morning light","resolution":"1k","aspect_ratio":"3:2"}' ``` ```python import os import requests response = requests.post( "https://api.seedrouter.ai/v1/images/generations", headers={"Authorization": f"Bearer {os.environ['SEEDROUTER_API_KEY']}"}, json={"model": "flux-3-image-klein", "prompt": "An amber bottle on pale limestone in soft morning light", "resolution": "1k", "aspect_ratio": "3:2"}, timeout=60, ) response.raise_for_status() task = response.json() print(task["id"]) ``` ```javascript const response = await fetch('https://api.seedrouter.ai/v1/images/generations', { method: 'POST', headers: { Authorization: `Bearer ${process.env.SEEDROUTER_API_KEY}`, 'Content-Type': 'application/json' }, body: JSON.stringify({ model: 'flux-3-image-klein', prompt: 'An amber bottle on pale limestone in soft morning light', resolution: '1k', aspect_ratio: '3:2' }), }); if (!response.ok) throw new Error(`Request failed: ${response.status}`); const task = await response.json(); console.log(task.id); ``` ```php true, CURLOPT_RETURNTRANSFER => true, CURLOPT_HTTPHEADER => ['Authorization: Bearer ' . getenv('SEEDROUTER_API_KEY'), 'Content-Type: application/json'], CURLOPT_POSTFIELDS => json_encode(['model' => 'flux-3-image-klein', 'prompt' => 'An amber bottle on pale limestone in soft morning light', 'resolution' => '1k', 'aspect_ratio' => '3:2']), ]); $response = curl_exec($ch); if ($response === false) throw new RuntimeException('Submission could not be confirmed'); echo $response; curl_close($ch); ``` ## Endpoint and headers `POST https://api.seedrouter.ai/v1/images/generations` | Header | Value | | ------------- | --------------------- | | Authorization | `Bearer YOUR_API_KEY` | | Content-Type | `application/json` | Keep the key on your server. An HTTP success acknowledges a task; it does not mean that its image is ready. ## Parameters There are 11 accepted fields. Only `model` and `prompt` are required. Omit optional fields to use their defaults; `null` is not accepted. | Field | Type | Default | Constraint | | ------------------ | ------------ | -------- | ------------------------------------------------------------------------------------------ | | `model` | string | Required | `flux-3-image-klein` | | `prompt` | string | Required | Non-empty image description or edit instruction | | `image_urls` | string array | None | At most 10 public HTTP(S) image URLs, without credentials; empty array means no references | | `aspect_ratio` | string | `auto` | A listed ratio; also accepts forms such as `16x9` | | `size` | string | None | Compatibility alias for aspect ratio; prefer `aspect_ratio` and send only one | | `resolution` | string | `1k` | `768sq`, `1k`, `1.5k`, `2k`, `4k`; case insensitive; `768` aliases `768sq` | | `safety_tolerance` | integer | `2` | 0–4; 0 is strictest | | `seed` | integer | Random | 0–4294967295; explicit 0 is preserved | | `steps` | integer | `16` | 1–16 | | `output_format` | string | `jpeg` | `jpeg`, `png`; `jpg` aliases `jpeg` | | `n` | integer | `1` | Only 1 | Ratios: `auto`, `21:9`, `2:1`, `16:9`, `3:2`, `7:5`, `4:3`, `5:4`, `1:1`, `4:5`, `3:4`, `5:7`, `2:3`, `9:16`, `1:2`, `9:21`. The Playground has a fixed model and ten input controls, including `n` fixed at 1. Safety values above 2 are API only, except for administrators. ## Modes and constraints No references means text-to-image. One reference enables editing; multiple references enable composition from several images. With `auto`, edits follow the first reference's aspect ratio. Text-only generation uses the prompt to select a frame, falling back to `1:1` when no frame is determined. Resolution defaults to `1k` in every mode. Resolution tiers represent approximate image scale: 768sq is about 768 × 768; 1K is about 1 MP; 1.5K about 2 MP; 2K about 4 MP; 4K about 16 MP. Inspect the returned file for actual dimensions. This endpoint does not accept `width`, `height`, pixel dimensions in `size`, `negative_prompt`, `guidance`, `grounding`, `prompt_upsampling`, `mask`, or `mask_url`. Unknown fields return HTTP 400 before billing. WebP output, base64 input, streaming, and callbacks are not offered. ## Reference images and regional edits Upload references to a public URL before submitting. The request body contains URLs, never file bytes or data URLs. ```json { "model": "flux-3-image-klein", "prompt": "Use Image 1 as the subject and Image 2 as the setting; match the perspective and light", "image_urls": ["https://example.com/subject.png", "https://example.com/setting.png"], "aspect_ratio": "auto", "resolution": "2k", "seed": 0, "steps": 16, "output_format": "png" } ``` Replace these placeholder URLs with your own accessible images. References are ordered: `ref_image_0` is the first. Bounding-box instructions are part of the `prompt` string, not a separate request field. Coordinates use `[y1, x1, y2, x2]` normalized to 0–1000. A layout object can contain `id`, `bbox`, and `desc`; an edit can use `id`, `from`, `src_bbox`, `tgt_bbox`, and `desc`. JSON-encode the complete request so quotes inside the prompt are escaped correctly. ## Billing One successful request is one image. The selected resolution alone sets the price; steps, seed, aspect ratio, reference count, and format do not add fees. Text-to-image and editing have the same rate. Failed requests are not charged. See [live pricing](https://seedrouter.ai/models/flux-3-image-klein#pricing). ## Task response and polling Submission: ```json {"id":"task_example","model":"flux-3-image-klein","status":"processing"} ``` ```bash curl https://api.seedrouter.ai/v1/tasks/task_example \ -H "Authorization: Bearer $SEEDROUTER_API_KEY" ``` Completed task (illustrative URL): ```json { "id": "task_example", "model": "flux-3-image-klein", "status": "completed", "output": {"data": [{"url": "https://file.deepytb.com/generated/example.png"}]} } ``` Read `output.data[0].url`. Allow up to ten minutes for generation, especially at 4K. Polling is read-only; a client timeout is not permission to submit another paid request. Public task responses do not include costs or account balances. ## Errors HTTP errors use `{"error": {"code": integer, "message": string}}`. See the [shared error directory](https://seedrouter.ai/docs/errors). A failed task exposes its error alongside `status: "failed"`. Correct invalid parameters before resubmitting; retain the task ID when checking a submitted request. ## Tips and related guides Use positive descriptions and name the regions or details to preserve. Lower steps may alter quality without reducing the price. Compare one change at a time. * [FLUX 3 Image Klein Playground](https://seedrouter.ai/models/flux-3-image-klein) * [Download, weights, and ComfyUI guide](https://seedrouter.ai/blog/flux-3-image-klein-download) * [Task lifecycle](https://seedrouter.ai/docs/api/tasks)