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black-forest-labs/flux-2-klein-9b-lora/text-to-image

FLUX.2 Klein 9B LoRA text to image runs Black Forest Labs' step-distilled FLUX.2 [klein] 9B with up to three of your own LoRA files. Nine aspect ratios at 1k or 2k, about ten seconds per image, and no content filter.

From $0.018/image
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Quickstart

Examples use the selected endpoint’s public parameter definitions. Replace the API key and example media, then send the request from your server.

SDKs & integrations
POSThttps://api.spicyapi.ai/api/v1/jobs/createTask

API authentication

Keep the API key in the server environment variable SPICY_API_KEY. Use Bearer authentication and Content-Type: application/json for JSON requests.

Authorization: Bearer $SPICY_API_KEY
FLUX.2 Klein 9B LoRA · Text to Image · Sample output
Sample outputUse this example
# Generate the idempotency key once; reuse it when retrying after a lost response.
export SPICY_IDEMPOTENCY_KEY="${SPICY_IDEMPOTENCY_KEY:-$(uuidgen)}"
curl -X POST https://api.spicyapi.ai/api/v1/jobs/createTask \
  -H "Authorization: Bearer $SPICY_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $SPICY_IDEMPOTENCY_KEY" \
  -d '{
  "model": "black-forest-labs/flux-2-klein-9b-lora/text-to-image",
  "input": {
    "aspect_ratio": "1:1",
    "prompt": "A ceramic teapot on a linen cloth, soft window light, muted palette",
    "resolution": "1k"
  }
}'

# Copy data.taskId from the response into TASK_ID, then poll the status.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.spicyapi.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
  -H "Authorization: Bearer $SPICY_API_KEY"

Generated from this model’s input schema — the same one the API validates every request against.

Input parameters

Place these fields inside the request body’s input object. Names and types match the API. Do not assume a default when none is specified.

promptstringRequired

Required, up to 5,000 characters. Put the LoRA's trigger phrase first, then describe subject, clothing, place, light and lens in sentences. There is no negative prompt, so say what you want.

Default
Not specified
Constraints
minLength:1
maxLength:5000
seedintegerOptional

Optional, 0 to 2,147,483,647. Reuse it to compare one change at a time; in our tests the same seed gave the same or a near-identical picture.

Default
Not specified
Constraints
minimum:0
maximum:2147483647
lorasarray<object>Optional

Up to three {path, scale} entries trained for FLUX.2 [klein] 9B, distilled or Base; scale 0 to 4, 1 by default. In our tests 0.5 was faint and 4 broke the picture. Use a public direct link to the .safetensors file. Does not change the price.

Default
[]
Constraints
maxItems:3
resolutionstringOptional

1k (default) is about one megapixel, for example 1344 x 768 or 1024 x 1024; 2k puts 2048 pixels on the long side, for example 2048 x 1152. Both cost the same.

Default
"1k"
Allowed values
"1k""2k"
aspect_ratiostringOptional

Nine shapes from 21:9 to 9:21; 1:1 by default. The shape does not change the price.

Default
"1:1"
Allowed values
"1:1""16:9""9:16""4:3""3:4""3:2""2:3""21:9""9:21"

Track the task

HTTP 202 means the task was accepted, not completed. Save the returned taskId and query that task. Do not create another task while waiting for its result.

Accepted response
HTTP/1.1 202 Accepted
Location: /api/v1/jobs/recordInfo?taskId=job_01k3m8x9q2z4v7n5p6r8s0t1w3

{
  "code": 200,
  "msg": "success",
  "request_id": "req_example_create",
  "data": {
    "taskId": "job_01k3m8x9q2z4v7n5p6r8s0t1w3",
    "state": "queued",
    "estimatedCost": "0.750000"
  }
}

The accepted response includes the estimate so your app can show the same amount in task history and billing.

Read the job
curl --get "https://api.spicyapi.ai/api/v1/jobs/recordInfo" \
  --data-urlencode "taskId=$TASK_ID" \
  -H "Authorization: Bearer $SPICY_API_KEY"

Start polling at about 2 seconds and gradually increase the interval. Stop at a terminal state. After a connection failure, query the original taskId. Retry creation only with the original idempotency key and body.

Or let the callback find you
import { verifyWebhook } from "@spicyapi/sdk";

// express.raw keeps the bytes we signed; express.json never matches.
app.post("/hooks/spicy", express.raw({ type: "application/json" }), (req, res) => {
  const { payload } = verifyWebhook({
    rawBody: req.body,
    timestamp: req.header("X-Webhook-Timestamp"),
    signature: req.header("X-Webhook-Signature"),
    payloadVersion: Number(req.header("X-Webhook-Payload-Version")),
    secret: process.env.SPICY_WEBHOOK_SECRET,
  });
  res.status(200).end();
  void handleFinishedTask(payload);
});

Pass callBackUrl when you create the task and the finished record is POSTed to you — no polling loop at all. Every delivery carries X-Webhook-Timestamp, X-Webhook-Signature and X-Webhook-Payload-Version. The signature is a base64 HMAC-SHA256 over taskId.timestamp.sha256(body), so it must be checked against the raw bytes: parsing the JSON and re-serialising it changes them and the check will fail. Failed deliveries are retried, so the same taskId can arrive twice — make the handler idempotent. Answer 2xx first and do the work afterwards; a slow handler is treated as a failed delivery.

Read the result

Consume output only when state is succeeded. On failure, use errorCode, errorMessage and request_id to investigate. Example costs and states do not represent an actual bill.

Completed response example
{
  "code": 200,
  "msg": "success",
  "request_id": "req_example_record",
  "data": {
    "taskId": "job_01k3m8x9q2z4v7n5p6r8s0t1w3",
    "model": "black-forest-labs/flux-2-klein-9b-lora/text-to-image",
    "state": "succeeded",
    "output": {
      "assets": [
        {
          "key": "tasks/2026/08/28/job_01k3m8x9q2z4v7n5p6r8s0t1w3/3f7a1c9e5b2d48f0a6c1e3d5b7f9a1c3.png",
          "mime": "image/png",
          "url": "https://example.r2.cloudflarestorage.com/results/job_01k3m8x9q2z4v7n5p6r8s0t1w3/result.png?X-Amz-Signature=SIGNATURE_FROM_RESPONSE",
          "expiresAt": "2026-08-28T12:20:08.000Z"
        }
      ]
    },
    "cost": "0.750000",
    "settled": true,
    "createdAt": "2026-08-28T12:00:00Z",
    "completedAt": "2026-08-28T12:00:30Z"
  }
}

For each available asset, open or download assets[].url directly without an API Authorization header. The signed URL expires at expiresAt; poll the task again to refresh it while the asset remains within its retention period. A pending or unavailable asset has no URL. Treat signed URLs as private.

SDKs & integrations

Use SpicyAPI in your app, terminal, AI assistant or visual workflow. Choose a setup guide below.

SDKs
TypeScript · Python · Go · PHP · Java
CLI
Terminal commands and automation scripts.
MCP
Claude Code · Cursor · Codex
Agent Skill
Reusable instructions for your AI assistant.
n8n
Self-hosted community nodes and importable HTTP Request templates for n8n Cloud.
ComfyUI
Image, video and audio workflows on a node canvas.

More integrations

SillyTavernTelegram / DiscordApp proxyOpenAI SDKLangChainVercel AI SDK
Browse ready-to-use workflows

Use it in ComfyUI

Install the SpicyAPI nodes from ComfyUI Manager or with the command below, then search for FLUX.2 Klein 9B LoRA · Text to Image on the canvas. The node has the same options as this page and shows its price before it runs.

cd ComfyUI/custom_nodes
git clone https://github.com/spicyapi-ai/comfyui-spicyapi
Workflow examplesSetup guideSource on GitHub