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 image. The first generated megapixel is charged $0.014. Each subsequent megapixel is charged $0.001.
Modalities
Price
$0.014/megapixel
Context
41K
Released
Jan 14, 2026
This model is hosted by one provider. OpenRouter forwards every request to it directly — no routing decisions to make.
The average price customers actually pay for this model, next to the prices providers post. Caching and discounts mean the price actually paid is often well below the listed one.
Throughput is how fast the model writes (tokens per second — higher is better). Latency is total round-trip time (lower is better). TTFT is time-to-first-token — how long before you see anything appear (lower is better).
Uptime is the percentage of the past 3 days that at least one provider was responding to requests. Availability is the percentage of time that inference was successfully served. OpenRouter continuously monitors and uses the next-best provider when one returns an error.
Scores on standardized evaluations. Higher percentages are better — and rank percentile shows where this model lands among all models on OpenRouter.
| Source | Benchmark | Score |
|---|---|---|
| Artificial Analysis | FLUX.2 [klein] 4B Elo | 864 |
| Design Arena | FLUX.2 Klein 4B Models Arena Graphic Design Elo | 1004 |
| Design Arena | FLUX.2 Klein 4B Models Arena Image Elo | 1065 |
| Design Arena | FLUX.2 Klein 4B Models Arena Logo Elo | 1059 |
Public apps that send the most traffic to this model. Good signal for what real production workloads look like — and a hint at which use cases this model is best suited for.
Token volume and request traffic to this model over time.
Drop-in code to call this model. OpenRouter's API is OpenAI-compatible — most SDKs work by just swapping the base URL. The only thing that changes between models is the model slug below.
| $0.014 | 5.79s |
End-to-end latency
5.79s
P50, best provider
100.00%
99.89%
When an error occurs in an upstream provider, we can recover by routing to another healthy provider, if your request filters allow it. You can access per-provider uptime data programmatically through the Endpoints API. Learn more about our load balancing and customization options.
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 image. The first generated megapixel is charged $0.014. Each subsequent megapixel is charged $0.001.
FLUX.2 Klein 4B costs $0.014/megapixel.
FLUX.2 Klein 4B supports the 1:1, 4:3, 3:4, 3:2, 2:3, 16:9 and 2 more aspect ratios and returns PNG and JPEG images.
FLUX.2 Klein 4B accepts text and images as input and returns images. Up to 4 reference images can be attached to one request for image editing.
FLUX.2 Max, FLUX.2 Flex and FLUX.2 Pro are other image models from Black Forest Labs.
FLUX.2 Klein 4B was released on January 14, 2026.