Black Forest LabsImageReleased 14 January 2026
FLUX.2 Klein 4B pricing, context and benchmark
FLUX.2 [klein] 4B is the fastest and most cost-effective model in the FLUX.2 family, optimized for high-throughput use cases while maintaining excellent image quality.
41K
Input context
n/a
Output context
$0.014
Per megapixel
1
Providers
n/a
AA index
01 · Model Overview
Everything that matters, in one table
Context, pricing, cache, modalities and tooling, from the model registry and Artificial Analysis.
| Model | FLUX.2 Klein 4B |
| Model ID | black-forest-labs/flux.2-klein-4b |
| Provider | Black Forest Labs |
| Release date | 14 January 2026 |
| Status | Generally available |
| Input context | 40,960 tokens |
| Output context | Provider default |
| Official input pricing | Free per 1M tokens |
| Official output pricing | Free per 1M tokens |
| Cache read pricing | Not published |
| Market input pricing | Free per 1M (cheapest route) |
| Market output pricing | Free per 1M (cheapest route) |
| Input modalities | text · image |
| Output modalities | image |
| Reasoning control | Not exposed |
| Tool support | Text generation only |
| Tokenizer | Other |
| Provider routes | 1 endpoint |
| Artificial Analysis index | Not published |
| Speed | Not published |
| Knowledge cutoff | Not publicly stated |
Input and output support
| Modality | Input | Output | Billed at |
|---|---|---|---|
| Text | ✓ yes | no | Free in |
| Image | ✓ yes | ✓ yes | Free in |
| Audio | no | no | not supported |
| Video | no | no | not supported |
| File (PDF) | no | no | not supported |
02 · Overview
What is FLUX.2 Klein 4B?
FLUX.2 [klein] 4B is the fastest and most cost-effective model in the FLUX.2 family, optimized for high-throughput use cases while maintaining excellent image quality.
Pricing is based on the output...
FLUX.2 Klein 4B carries a 41K token window, uses the Other tokenizer and is served by Black Forest Labs. On Hoodgen it sits in the Image tier of the model menu next to its siblings, so you can switch mid conversation without losing the thread.
03 · Release
Release and what changed from the previous version
Released14 January 2026
| Property | Seedream 4.5 | FLUX.2 Klein 4B | Change |
|---|---|---|---|
| Released | Dec 2025 | Jan 2026 | Newer release |
| Context | 4K | 41K | Changed |
| Max output | n/a | n/a | Unchanged |
| Input price | Free | Free | Unchanged |
| Output price | Free | Free | Unchanged |
| Input modalities | image, text | text, image | Unchanged |
| AA index | n/a | n/a | Newer benchmark run |
04 · Capabilities
Features and capabilities
◉
Vision
Screenshots, charts and photographed documents are read at the text token rate.
07 · Use cases
What can you do with FLUX.2 Klein 4B?
Everyday writing
Drafts, rewrites, summaries and replies.
Research
Source material condensed with the key numbers kept.
Chat
General questions where latency and cost both matter.
Tooling inside Hoodgen
Writer, Humanizer, Coding and the rest of the tool suite.
09 · Pricing
FLUX.2 Klein 4B pricing
Official pricing
Per megapixel
$0.014 / megapixel
- Image Output: $0.014 per megapixel
- image output from text, image input
Cheapest route
Free / 1M in
Free / 1M out
- 1 route on OpenRouter
- What Hoodgen routes to first
- Same model, lower bill
Market pricing, every route
| Provider | Tier | Input | Output | Cache read | Uptime 24h |
|---|---|---|---|---|---|
| Black Forest Labs | standard | n/a | n/a | n/a | 100.0% |
API pricing and cost calculator
| Rate | Per call | Total | Credits |
|---|---|---|---|
| Cheapest route | $0.0000 | $0.00 | 1 |
| List price | $0.0000 | $0.00 | 1 |
10 · Developers
API and developer information
| Model ID | black-forest-labs/flux.2-klein-4b |
| Endpoint | https://openrouter.ai/api/v1/chat/completions |
| Parameters | prompt and max_tokens |
| Streaming | Yes, server sent events |
| Modality string | text+image->image |
| Max prompt tokens | 40,960 |
| Max completion tokens | provider default |
curl https://openrouter.ai/api/v1/chat/completions \
-H "Authorization: Bearer $OPENROUTER_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "black-forest-labs/flux.2-klein-4b",
"messages": [{ "role": "user", "content": "Summarise this document." }],
"max_tokens": 1024
}'11 · Limitations
Model limitations
| Output cap | Provider default tokens per request. Long deliverables have to be chunked. |
| Benchmarks not published | Artificial Analysis does not publish an Intelligence Index for this release, so no benchmark score is claimed here. |
| Knowledge cutoff | The provider does not state a fixed cutoff for every release. Verify very recent events against search. |
12 · Comparison
FLUX.2 Klein 4B vs other Black Forest Labs models
| Model | Context | Input /1M | Output /1M | AA index | Released |
|---|---|---|---|---|---|
| FLUX.2 Klein 4B | 41K | Free | Free | n/a | Jan 2026 |
| GPT Image 1 | 400K | $10 | $10 | n/a | Jun 2026 |
| GPT Image 2.6 Sunburst | 400K | $8 | $8 | n/a | Nov 2026 |
| GPT Image 2.6 Flare | 400K | $8 | $8 | n/a | Nov 2026 |
| GPT Image 2 | 400K | $8 | $8 | n/a | Jun 2026 |
| GPT Image 2.5 Flare | 400K | $8 | $8 | n/a | Sept 2026 |
13 · Privacy
Privacy and data policy
- On Hoodgen, prompts and attachments answer that request and stay in your conversation history so you can reopen it. They are not used to train models.
- Requests route through OpenRouter to Black Forest Labs and are covered by that provider's API terms.
- Do not paste secrets or personal data you would not send to any hosted model.
14 · FAQ
FLUX.2 Klein 4B questions, answered
FLUX.2 Klein 4B is a image model from Black Forest Labs, released 14 January 2026. FLUX.2 [klein] 4B is the fastest and most cost-effective model in the FLUX.2 family, optimized for high-throughput use cases while maintaining excellent image quality.
✦
Start chatting with FLUX.2 Klein 4B
Free to try on Hoodgen AI, with a live credit estimate before every send. No API key, no setup.