Blackforestlabs Flux 2 Klein 9B API | Pricing & Docs

blackforestlabs/flux-2-klein/9b/text-to-image

Generate high-fidelity images or edits from prompts and references with sub-second speed, sharp text rendering, and multi-reference consistency for real-time design and branding workflows.

1. Get started

Use RunComfy's API to run blackforestlabs/flux-2-klein/9b/text-to-image. For accepted inputs and outputs, see the model's schema.

curl --request POST \
  --url https://model-api.runcomfy.net/v1/models/blackforestlabs/flux-2-klein/9b/text-to-image \
  --header "Content-Type: application/json" \
  --header "Authorization: Bearer <token>" \
  --data '{
    "prompt": "A vibrant hummingbird mid-flight sipping nectar from a bright pink hibiscus flower, iridescent emerald and sapphire feathers catching the morning sun, soft bokeh tropical garden background, macro photography, razor-sharp detail, cinematic lighting"
  }'

2. Authentication

Set the YOUR_API_TOKEN environment variable with your API key (manage keys in your Profile) and include it on every request as a Bearer token via the Authorization header: Authorization: Bearer $YOUR_API_TOKEN.

3. API reference

Submit a request

Submit an asynchronous generation job and immediately receive a request_id plus URLs to check status, fetch results, and cancel.

curl --request POST \
  --url https://model-api.runcomfy.net/v1/models/blackforestlabs/flux-2-klein/9b/text-to-image \
  --header "Content-Type: application/json" \
  --header "Authorization: Bearer <token>" \
  --data '{
    "prompt": "A vibrant hummingbird mid-flight sipping nectar from a bright pink hibiscus flower, iridescent emerald and sapphire feathers catching the morning sun, soft bokeh tropical garden background, macro photography, razor-sharp detail, cinematic lighting"
  }'

Monitor request status

Fetch the current state for a request_id ("in_queue", "in_progress", "completed", or "cancelled").

curl --request GET \
  --url https://model-api.runcomfy.net/v1/requests/{request_id}/status \
  --header "Authorization: Bearer <token>"

Retrieve request results

Retrieve the final outputs and metadata for the given request_id; if the job is not complete, the response returns the current state so you can continue polling.

curl --request GET \
  --url https://model-api.runcomfy.net/v1/requests/{request_id}/result \
  --header "Authorization: Bearer <token>"

Cancel a request

Cancel a queued job by request_id; in-progress jobs cannot be cancelled.

curl --request POST \
  --url https://model-api.runcomfy.net/v1/requests/{request_id}/cancel \
  --header "Authorization: Bearer <token>"

4. File inputs

Hosted file (URL)

Provide a publicly reachable HTTPS URL. Ensure the host allows server-side fetches (no login/cookies required) and isn't rate-limited or blocking bots. Recommended limits: images ≤ 50 MB (~4K), videos ≤ 100 MB (~2–5 min @ 720p). Prefer stable or pre-signed URLs for private assets.

5. Schema

Input schema

{
  "type": "object",
  "title": "Input schema",
  "required": [
    "prompt"
  ],
  "properties": {
    "prompt": {
      "title": "Prompt",
      "description": "",
      "type": "string",
      "default": "A vibrant hummingbird mid-flight sipping nectar from a bright pink hibiscus flower, iridescent emerald and sapphire feathers catching the morning sun, soft bokeh tropical garden background, macro photography, razor-sharp detail, cinematic lighting"
    },
    "steps": {
      "title": "Steps",
      "description": "The number of diffusion steps; higher values can improve quality but take longer.",
      "type": "integer",
      "minimum": 1,
      "maximum": 100,
      "default": 25
    },
    "width": {
      "title": "Width",
      "description": "The width in pixels of the output image.",
      "type": "integer",
      "minimum": 512,
      "maximum": 1536,
      "default": 1024
    },
    "height": {
      "title": "Height",
      "description": "The height in pixels of the output image.",
      "type": "integer",
      "minimum": 512,
      "maximum": 1536,
      "default": 1024
    }
  }
}

Output schema

{
  "output": {
    "type": "object",
    "properties": {
      "image": {
        "type": "string",
        "format": "uri",
        "description": "single image URL"
      },
      "video": {
        "type": "string",
        "format": "uri",
        "description": "single video URL"
      },
      "images": {
        "type": "array",
        "description": "multiple image URLs",
        "items": {
          "type": "string",
          "format": "uri"
        }
      },
      "videos": {
        "type": "array",
        "description": "multiple video URLs",
        "items": {
          "type": "string",
          "format": "uri"
        }
      }
    }
  }
}

RunComfy

RunComfy is the premier ComfyUI platform, offering ComfyUI online environment and services, along with ComfyUI workflows featuring stunning visuals. RunComfy also provides AI Models, enabling artists to harness the latest AI tools to create incredible art.

1. Get started

Use RunComfy's API to run blackforestlabs/flux-2-klein/9b/text-to-image. For accepted inputs and outputs, see the model's schema.

curl --request POST \
  --url https://model-api.runcomfy.net/v1/models/blackforestlabs/flux-2-klein/9b/text-to-image \
  --header "Content-Type: application/json" \
  --header "Authorization: Bearer <token>" \
  --data '{
    "prompt": "A vibrant hummingbird mid-flight sipping nectar from a bright pink hibiscus flower, iridescent emerald and sapphire feathers catching the morning sun, soft bokeh tropical garden background, macro photography, razor-sharp detail, cinematic lighting"
  }'

3. API reference

Submit a request

Submit an asynchronous generation job and immediately receive a request_id plus URLs to check status, fetch results, and cancel.

curl --request POST \
  --url https://model-api.runcomfy.net/v1/models/blackforestlabs/flux-2-klein/9b/text-to-image \
  --header "Content-Type: application/json" \
  --header "Authorization: Bearer <token>" \
  --data '{
    "prompt": "A vibrant hummingbird mid-flight sipping nectar from a bright pink hibiscus flower, iridescent emerald and sapphire feathers catching the morning sun, soft bokeh tropical garden background, macro photography, razor-sharp detail, cinematic lighting"
  }'

Monitor request status

Fetch the current state for a request_id ("in_queue", "in_progress", "completed", or "cancelled").

curl --request GET \
  --url https://model-api.runcomfy.net/v1/requests/{request_id}/status \
  --header "Authorization: Bearer <token>"

Retrieve request results

Retrieve the final outputs and metadata for the given request_id; if the job is not complete, the response returns the current state so you can continue polling.

curl --request GET \
  --url https://model-api.runcomfy.net/v1/requests/{request_id}/result \
  --header "Authorization: Bearer <token>"

Cancel a request

Cancel a queued job by request_id; in-progress jobs cannot be cancelled.

curl --request POST \
  --url https://model-api.runcomfy.net/v1/requests/{request_id}/cancel \
  --header "Authorization: Bearer <token>"

4. File inputs

Hosted file (URL)

5. Schema

Input schema

{
  "type": "object",
  "title": "Input schema",
  "required": [
    "prompt"
  ],
  "properties": {
    "prompt": {
      "title": "Prompt",
      "description": "",
      "type": "string",
      "default": "A vibrant hummingbird mid-flight sipping nectar from a bright pink hibiscus flower, iridescent emerald and sapphire feathers catching the morning sun, soft bokeh tropical garden background, macro photography, razor-sharp detail, cinematic lighting"
    },
    "steps": {
      "title": "Steps",
      "description": "The number of diffusion steps; higher values can improve quality but take longer.",
      "type": "integer",
      "minimum": 1,
      "maximum": 100,
      "default": 25
    },
    "width": {
      "title": "Width",
      "description": "The width in pixels of the output image.",
      "type": "integer",
      "minimum": 512,
      "maximum": 1536,
      "default": 1024
    },
    "height": {
      "title": "Height",
      "description": "The height in pixels of the output image.",
      "type": "integer",
      "minimum": 512,
      "maximum": 1536,
      "default": 1024
    }
  }
}

Output schema

{
  "output": {
    "type": "object",
    "properties": {
      "image": {
        "type": "string",
        "format": "uri",
        "description": "single image URL"
      },
      "video": {
        "type": "string",
        "format": "uri",
        "description": "single video URL"
      },
      "images": {
        "type": "array",
        "description": "multiple image URLs",
        "items": {
          "type": "string",
          "format": "uri"
        }
      },
      "videos": {
        "type": "array",
        "description": "multiple video URLs",
        "items": {
          "type": "string",
          "format": "uri"
        }
      }
    }
  }
}

Generate high-fidelity images or edits from prompts and references with sub-second speed, sharp text rendering, and multi-reference consistency for real-time design and branding workflows.

Table of contents

1. Get started

2. Authentication

3. API reference

Submit a request

Monitor request status

Retrieve request results

Cancel a request

4. File inputs

Hosted file (URL)

5. Schema

Input schema

Output schema

Generate high-fidelity images or edits from prompts and references with sub-second speed, sharp text rendering, and multi-reference consistency for real-time design and branding workflows.

Table of contents

1. Get started

2. Authentication

3. API reference

Submit a request

Monitor request status

Retrieve request results

Cancel a request

4. File inputs

Hosted file (URL)

5. Schema

Input schema

Output schema

Flux 2 Klein 9B: High-Fidelity 4-Step Text-to-Image Generation | RunComfy

Generate high-fidelity images or edits from prompts and references with sub-second speed, sharp text rendering, and multi-reference consistency for real-time design and branding workflows.

Table of contents

1. Get started

2. Authentication

3. API reference

Submit a request

Monitor request status

Retrieve request results

Cancel a request

4. File inputs

Hosted file (URL)

5. Schema

Input schema

Output schema

Flux 2 Klein 9B: High-Fidelity 4-Step Text-to-Image Generation | RunComfy

Generate high-fidelity images or edits from prompts and references with sub-second speed, sharp text rendering, and multi-reference consistency for real-time design and branding workflows.

Table of contents

1. Get started

2. Authentication

3. API reference

Submit a request

Monitor request status

Retrieve request results

Cancel a request

4. File inputs

Hosted file (URL)

5. Schema

Input schema

Output schema