GPT-6 Luna vs Step-3.5-Flash
GPT-6 Luna leads the LLM Stats Score 44.5 to 37.1. Step-3.5-Flash is 1.1x cheaper per token.
OpenAI · StepFun · Updated for 2026
Which is better?
GPT-6 Luna leads the overall LLM Stats Score 44.5 to 37.1, ranking #40 overall.
On price, Step-3.5-Flash is roughly 1.1x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-6 Luna also accepts a larger context window (1,050,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose GPT-6 Luna
- overall performance matters — it scores 44.5 and ranks #40 on LLM Stats
- your work emphasizes agents — it leads those capability indexes
- you process long inputs — it offers a 1,050,000 token context window
- you want the most recent training data — it shipped Sep 2026
Choose Step-3.5-Flash
- cost matters — it's about 1.1x cheaper per token
- you need open weights you can self-host or fine-tune
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
5 reported for GPT-6 Luna · 7 for Step-3.5-Flash
GPT-6 Luna and Step-3.5-Flashdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-6 Luna ($0.10/1M tokens) costs the same as Step-3.5-Flash ($0.10/1M tokens).
For output processing, GPT-6 Luna ($0.50/1M tokens) is 1.3x more expensive than Step-3.5-Flash ($0.40/1M tokens).
In conclusion, GPT-6 Luna is more expensive than Step-3.5-Flash.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-6 Luna accepts 1,050,000 input tokens compared to Step-3.5-Flash's 65,536 tokens. GPT-6 Luna can generate longer responses up to 128,000 tokens, while Step-3.5-Flash is limited to 8,192 tokens.
Input capabilities
Documented input modalities across available providers
GPT-6 Luna supports multimodal inputs, whereas Step-3.5-Flash does not.
GPT-6 Luna can handle both text and other forms of data like images, making it suitable for multimodal applications.
GPT-6 Luna
Step-3.5-Flash
License
Usage and distribution terms
GPT-6 Luna is licensed under a proprietary license, while Step-3.5-Flash uses Apache 2.0.
License differences may affect how you can use these models in commercial or open-source projects.
Proprietary
Closed source
Apache 2.0
Open weights
Release Timeline
When each model was launched
GPT-6 Luna was released on 2026-09-22, while Step-3.5-Flash was released on 2026-02-02.
GPT-6 Luna is 8 months newer than Step-3.5-Flash.
Sep 22, 2026
0 days ago
7mo newerFeb 2, 2026
7 months ago
Knowledge Cutoff
When training data ends
GPT-6 Luna has a documented knowledge cutoff of 2026-05-18, while Step-3.5-Flash's cutoff date is not specified.
We can confirm GPT-6 Luna's training data extends to 2026-05-18, but cannot make a direct comparison without Step-3.5-Flash's cutoff date.
May 2026
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Provider Availability
GPT-6 Luna is available from OpenAI. Step-3.5-Flash is available from StepFun.
GPT-6 Luna
Step-3.5-Flash
Outputs Comparison
Judge for yourself.
Run your own prompts against GPT-6 Luna and Step-3.5-Flash side-by-side, then vote on the output you prefer.
FAQ
Common questions about GPT-6 Luna vs Step-3.5-Flash.