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Pricing: $0.025/image. Endpoint: POST /v1/models/black-forest-labs/flux-1-dev/edit/runs.
Image-to-image edits with FLUX.1 [dev]. Pass a source image plus a prompt and a transformation strength to redirect the composition while preserving subject identity.

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Overview

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Pricing

  • Base price: $0.025/image
  • Note: per image at 1024x1024

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FLUX.1 [dev] Edit API

Endpoint: POST /v1/models/black-forest-labs/flux-1-dev/edit/runs

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Run the model

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Python

import requests

response = requests.post(
    "https://api.runflow.io/v1/models/black-forest-labs/flux-1-dev/edit/runs",
    headers={"Authorization": "Bearer RUNFLOW_API_KEY"},
    json={
        "input": {
            "steps": 28,
            "prompt": "Transform the engineer into a samurai warrior with traditional kabuto armor and a katana, dramatic lighting, photoreal cinematic style",
            "strength": 0.85,
            "image_b64": "https://public.runflow.io/images/models/_shared/base-engineer.png"
        },
        "callback_url": "https://your-server.com/webhook"
    },
)

data = response.json()
print(data)

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Node.js

const response = await fetch(
  "https://api.runflow.io/v1/models/black-forest-labs/flux-1-dev/edit/runs",
  {
    method: "POST",
    headers: {
      "Authorization": "Bearer RUNFLOW_API_KEY",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
        "input": {
            "steps": 28,
            "prompt": "Transform the engineer into a samurai warrior with traditional kabuto armor and a katana, dramatic lighting, photoreal cinematic style",
            "strength": 0.85,
            "image_b64": "https://public.runflow.io/images/models/_shared/base-engineer.png"
        },
        "callback_url": "https://your-server.com/webhook"
    }),
  }
);

const data = await response.json();
console.log(data);

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cURL

curl -X POST https://api.runflow.io/v1/models/black-forest-labs/flux-1-dev/edit/runs \
  -H "Authorization: Bearer $RUNFLOW_API_KEY" \
  -H "Content-Type: application/json" \
  --data-binary @- <<'JSON'
{
    "input": {
        "steps": 28,
        "prompt": "Transform the engineer into a samurai warrior with traditional kabuto armor and a katana, dramatic lighting, photoreal cinematic style",
        "strength": 0.85,
        "image_b64": "https://public.runflow.io/images/models/_shared/base-engineer.png"
    },
    "callback_url": "https://your-server.com/webhook"
}
JSON

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Request parameters

ParameterTypeRequiredDescription
inputobjectrequiredModel input parameters. See “Input schema” below.
callback_urlstring | nulloptionalWebhook URL - POSTed when the run reaches a terminal state.
metadataobject | nulloptionalArbitrary key-value pairs attached to the run.

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Input schema

FieldTypeRequiredAllowed valuesDescription
promptstringrequiredAnyText description of the image to generate.
strengthfloatoptionalAnyHow much to transform the source image. 0 keeps it intact; 1 ignores it. 0.5-0.8 typical.
stepsintegeroptionalAnyNumber of diffusion steps. Higher = slightly more quality, slower generation.
guidancefloatoptionalAnyHigher values make the model follow the prompt more strictly.
seedintegeroptionalAnyRandom positive integer for reproducible results. Leave blank to randomise.
image_b64imagerequiredAnyBase64-encoded image or image URL. Used as the reference for image-to-image edits.

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Output schema

FieldTypeDescription
outputsjsonUnified output array. One entry per generated artifact with url/type/width/height/content_type.
seedjsonDeterministic seed used for generation, or null if not returned.
timingjsonProvider timing info (inference_ms etc.), or null.
nsfw_detectedjsontrue if flagged as NSFW, false if cleared, null if not checked.

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Callback payload

When you provide a callback_url, Runflow POSTs to it once the run reaches a terminal state.
FieldTypeDescription
eventstringEvent type: “run.completed”, “run.failed”, or “run.cancelled”.
run_idstringThe unique identifier of the run.
statusstringTerminal status: “succeeded”, “failed”, or “cancelled”.
outputobject | nullThe run output. Null if the run failed or was cancelled.
duration_msnumber | nullTotal run duration in milliseconds.
created_atstring | nullISO 8601 timestamp when the run was created.
completed_atstring | nullISO 8601 timestamp when the run reached terminal state.
metadataobject | nullThe metadata object passed at run creation, if any.
  • Retries: 3 attempts with exponential backoff (1s, 2s). Retries on 5xx / network errors only.
  • Headers: Runflow-Request-Id is always sent. Runflow-Signature is sent if a signing secret is configured.

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Additional Resources

Browse all models

Browse the catalog.

Run lifecycle

Callbacks, polling, statuses.

Callbacks

Handle async results.

Pricing

How requests bill out.