OpenAI's fastest, most affordable GPT-5.6 tier for high-volume, latency-sensitive work.
StepFun's fast and efficient language model.
No shared demos for these models yet.
No captured outputs for these models yet.
Both GPT 5.6 Luna and Step 3.5 Flash are capable AI models. The best choice depends on your specific use case: consider pricing, context window, speed, and which capabilities (vision, reasoning, audio) you need.
Step 3.5 Flash has a lower blended cost. GPT 5.6 Luna: $1.00 input / $6.00 output. Step 3.5 Flash: $0.10 input / $0.30 output.
GPT 5.6 Luna has a larger context window: GPT 5.6 Luna supports 1.1M tokens vs Step 3.5 Flash at 262K tokens.
GPT 5.6 Luna supports vision/image input, but Step 3.5 Flash does not.
Key differences: Step 3.5 Flash is significantly cheaper; only GPT 5.6 Luna supports vision input. Compare full specs on this page.
If cost is your priority, choose the cheaper option. If you need the highest intelligence for complex tasks, pick the higher-scoring model. For long documents or codebases, choose the larger context window. You can try both GPT 5.6 Luna and Step 3.5 Flash for free on idapt.app to see which performs better for your specific needs.