You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
description: New ultra-fast FLUX.2 [klein] 4B model on Workers AI
4
+
date: 2025-01-15
5
+
---
6
+
7
+
We've partnered with Black Forest Labs (BFL) again to bring their optimized FLUX.2 [klein] 4B model to Workers AI! This distilled model offers faster generation and cost-effective pricing, while maintaining great output quality. With a fixed 4-step inference process, Klein 4B is ideal for rapid prototyping and real-time applications where speed matters.
8
+
9
+
Read the [BFL blog](https://bfl.ai/blog) to learn more about the model itself, or try it out yourself on our [multi modal playground](https://multi-modal.ai.cloudflare.com/).
10
+
11
+
Pricing documentation is available on the [model page](/workers-ai/models/flux-2-klein-4b/) or [pricing page](/workers-ai/platform/pricing/).
12
+
13
+
## Workers AI Platform specifics
14
+
15
+
The model hosted on Workers AI is optimized for speed with a **fixed 4-step inference process** and supports up to 4 image inputs. Since this is a distilled model, the `steps` parameter is fixed at 4 and cannot be adjusted. Like FLUX.2 [dev], this image model uses multipart form data inputs, even if you just have a prompt.
16
+
17
+
With the REST API, the multipart form data input looks like this:
The parameters you can send to the model are detailed here:
64
+
65
+
<details>
66
+
<summary>JSON Schema for Model</summary>
67
+
**Required Parameters**
68
+
69
+
-`prompt` (string) - Text description of the image to generate
70
+
71
+
**Optional Parameters**
72
+
73
+
-`input_image_0` (string) - Binary image
74
+
-`input_image_1` (string) - Binary image
75
+
-`input_image_2` (string) - Binary image
76
+
-`input_image_3` (string) - Binary image
77
+
-`guidance` (float) - Guidance scale for generation. Higher values follow the prompt more closely
78
+
-`width` (integer) - Width of the image, default `1024` Range: 256-1920
79
+
-`height` (integer) - Height of the image, default `768` Range: 256-1920
80
+
-`seed` (integer) - Seed for reproducibility
81
+
82
+
**Note:** Since this is a distilled model, the `steps` parameter is fixed at 4 and cannot be adjusted.
83
+
84
+
</details>
85
+
86
+
````
87
+
88
+
## Multi-Reference Images
89
+
90
+
The FLUX.2 klein-4b model supports generating images based on reference images, just like FLUX.2 [dev]. You can use this feature to apply the style of one image to another, add a new character to an image, or iterate on past generated images. You would use it with the same multipart form data structure, with the input images in binary. The model supports up to 4 input images.
91
+
92
+
For the prompt, you can reference the images based on the index, like `take the subject of image 1 and style it like image 0` or even use natural language like `place the dog beside the woman`.
93
+
94
+
Note: you have to name the input parameter as `input_image_0`, `input_image_1`, `input_image_2`, `input_image_3` for it to work correctly. All input images must be smaller than 512x512.
Copy file name to clipboardExpand all lines: src/content/docs/workers-ai/platform/pricing.mdx
+34-33Lines changed: 34 additions & 33 deletions
Display the source diff
Display the rich diff
Original file line number
Diff line number
Diff line change
@@ -54,46 +54,47 @@ The Price in Tokens column is equivalent to the Price in Neurons column - the di
54
54
|@cf/google/gemma-3-12b-it | $0.345 per M input tokens <br/> $0.556 per M output tokens | 31371 neurons per M input tokens <br/> 50560 neurons per M output tokens |
55
55
|@cf/qwen/qwq-32b | $0.660 per M input tokens <br/> $1.000 per M output tokens | 60000 neurons per M input tokens <br/> 90909 neurons per M output tokens |
56
56
|@cf/qwen/qwen2.5-coder-32b-instruct | $0.660 per M input tokens <br/> $1.000 per M output tokens | 60000 neurons per M input tokens <br/> 90909 neurons per M output tokens |
57
-
|@cf/qwen/qwen3-30b-a3b-fp8 | $0.051 per M input tokens <br/> $0.335 per M output tokens | 4625 neurons per M input tokens <br/> 30475 neurons per M output tokens |
58
-
|@cf/openai/gpt-oss-120b | $0.350 per M input tokens <br/> $0.750 per M output tokens | 31818 neurons per M input tokens <br/> 68182 neurons per M output tokens |
59
-
|@cf/openai/gpt-oss-20b | $0.200 per M input tokens <br/> $0.300 per M output tokens | 18182 neurons per M input tokens <br/> 27273 neurons per M output tokens |
60
-
|@cf/aisingapore/gemma-sea-lion-v4-27b-it | $0.351 per M input tokens <br/> $0.555 per M output tokens | 31876 neurons per M input tokens <br/> 50488 neurons per M output tokens |
61
-
|@cf/ibm-granite/granite-4.0-h-micro | $0.017 per M input tokens <br/> $0.112 per M output tokens | 1542 neurons per M input tokens <br/> 10158 neurons per M output tokens |
57
+
|@cf/qwen/qwen3-30b-a3b-fp8 | $0.051 per M input tokens <br/> $0.335 per M output tokens | 4625 neurons per M input tokens <br/> 30475 neurons per M output tokens|
58
+
|@cf/openai/gpt-oss-120b | $0.350 per M input tokens <br/> $0.750 per M output tokens | 31818 neurons per M input tokens <br/> 68182 neurons per M output tokens|
59
+
|@cf/openai/gpt-oss-20b | $0.200 per M input tokens <br/> $0.300 per M output tokens | 18182 neurons per M input tokens <br/> 27273 neurons per M output tokens|
60
+
|@cf/aisingapore/gemma-sea-lion-v4-27b-it | $0.351 per M input tokens <br/> $0.555 per M output tokens | 31876 neurons per M input tokens <br/> 50488 neurons per M output tokens|
61
+
|@cf/ibm-granite/granite-4.0-h-micro | $0.017 per M input tokens <br/> $0.112 per M output tokens | 1542 neurons per M input tokens <br/> 10158 neurons per M output tokens|
|@cf/black-forest-labs/flux-1-schnell | $0.0000528 per 512x512 tile <br/> $0.0001056 per step | 4.80 neurons per 512x512 tile <br/> 9.60 neurons per step |
79
-
|@cf/leonardo/lucid-origin | $0.006996 per 512x512 tile <br/> $0.000132 per step | 636.00 neurons per 512x512 tile <br/> 12.00 neurons per step |
80
-
|@cf/leonardo/phoenix-1.0 | $0.005830 per 512x512 tile <br/> $0.000110 per step | 530.00 neurons per 512x512 tile <br/> 10.00 neurons per step |
81
-
|@cf/black-forest-labs/flux-2-dev | $0.00021 per input 512x512 tile, per step <br/> $0.00041 per output 512x512 tile, per step | 18.75 neurons per input 512x512 tile, per step <br/> 37.50 neurons per output 512x512 tile, per step |
|@cf/black-forest-labs/flux-1-schnell | $0.0000528 per 512x512 tile <br/> $0.0001056 per step | 4.80 neurons per 512x512 tile <br/> 9.60 neurons per step |
79
+
|@cf/leonardo/lucid-origin | $0.006996 per 512x512 tile <br/> $0.000132 per step | 636.00 neurons per 512x512 tile <br/> 12.00 neurons per step |
80
+
|@cf/leonardo/phoenix-1.0 | $0.005830 per 512x512 tile <br/> $0.000110 per step | 530.00 neurons per 512x512 tile <br/> 10.00 neurons per step |
81
+
|@cf/black-forest-labs/flux-2-dev | $0.00021 per input 512x512 tile, per step <br/> $0.00041 per output 512x512 tile, per step | 18.75 neurons per input 512x512 tile, per step <br/> 37.50 neurons per output 512x512 tile, per step |
82
+
|@cf/black-forest-labs/flux-2-klein-4b | $0.000059 per input 512x512 tile <br/> $0.000287 per output 512x512 tile | 5.37 neurons per input 512x512 tile <br/> 26.05 neurons per output 512x512 tile |
|@cf/openai/whisper | $0.0005 per audio minute | 41.14 neurons per audio minute |
89
+
|@cf/openai/whisper-large-v3-turbo | $0.0005 per audio minute | 46.63 neurons per audio minute |
90
+
|@cf/myshell-ai/melotts | $0.0002 per audio minute | 18.63 neurons per audio minute |
91
+
|@cf/deepgram/aura-1 | $0.015 per 1k characters input <br/> | 1,363.64 neurons per 1k characters input <br/> |
92
+
|@cf/deepgram/nova-3 | $0.0052 per audio minute input <br/> | 472.73 neurons per audio minute input <br/> |
93
+
|@cf/deepgram/nova-3 (WebSocket)| $0.0092 per audio minute input <br/> | 836.36 neurons per audio minute input <br/> |
94
+
|@cf/pipecat-ai/smart-turn-v2 | $0.00033795 per audio minute input <br/> | 0.51 neurons per audio minute input <br/> |
95
+
|@cf/deepgram/aura-2-en | $0.030 per 1k characters input <br/> | 2727.27 neurons per 1k characters input <br/>|
96
+
|@cf/deepgram/aura-2-es | $0.030 per 1k characters input <br/> | 2727.27 neurons per 1k characters input <br/>|
97
+
|@cf/deepgram/flux (WebSocket)| $0.0077 per audio minute <br/> | 700.00 neurons per audio minute <br/>|
97
98
98
99
## Other model pricing
99
100
@@ -102,5 +103,5 @@ The Price in Tokens column is equivalent to the Price in Neurons column - the di
102
103
|@cf/huggingface/distilbert-sst-2-int8 | $0.026 per M input tokens | 2394 neurons per M input tokens |
103
104
|@cf/baai/bge-reranker-base | $0.003 per M input tokens | 283 neurons per M input tokens |
104
105
|@cf/meta/m2m100-1.2b | $0.342 per M input tokens <br/> $0.342 per M output tokens | 31050 neurons per M input tokens <br/> 31050 neurons per M output tokens |
105
-
|@cf/microsoft/resnet-50 | $2.51 per M images | 228055 neurons per M images |
106
-
|@cf/ai4bharat/indictrans2-en-indic-1B | $0.342 per M input tokens <br/> $0.342 per M output tokens | 31050 neurons per M input tokens <br/> 31050 neurons per M output tokens |
106
+
|@cf/microsoft/resnet-50 | $2.51 per M images | 228055 neurons per M images|
107
+
|@cf/ai4bharat/indictrans2-en-indic-1B | $0.342 per M input tokens <br/> $0.342 per M output tokens | 31050 neurons per M input tokens <br/> 31050 neurons per M output tokens |
Copy file name to clipboardExpand all lines: src/content/release-notes/workers-ai.yaml
+4Lines changed: 4 additions & 0 deletions
Original file line number
Diff line number
Diff line change
@@ -3,6 +3,10 @@ link: "/workers-ai/changelog/"
3
3
productName: Workers AI
4
4
productLink: "/workers-ai/"
5
5
entries:
6
+
- publish_date: "2025-01-15"
7
+
title: Black Forest Labs FLUX.2 [klein] 4b now available
8
+
description: |-
9
+
- [`@cf/black-forest-labs/flux-2-klein-4b`](/workers-ai/models/flux-2-klein-4b/) now available on Workers AI! Read [changelog](/changelog/2025-01-15-flux-2-klein-4b-workers-ai/) to get started
6
10
- publish_date: "2025-12-03"
7
11
title: Deepgram Flux promotional period over on Dec 8, 2025 - now has pricing
0 commit comments