AI model comparison
Step 5 Preview vs GPT-6 Luna
Pricing, context window, benchmarks, and features compared side by side. Or skip the guesswork and send one prompt to both.
StepFun
Step 5 Preview
Step 5 Preview is StepFun's flagship model for agentic work, built on a sparse Mixture-of-Experts architecture (27B active / 600B total parameters).
- Input / 1M
- $1
- Output / 1M
- $2.70
- Context
- 1M
OpenAI
GPT-6 Luna
GPT-6 Luna is the fast, cost-efficient model in OpenAI's GPT-6 series, positioned below GPT-6 Sol.
- Input / 1M
- $0.10
- Output / 1M
- $0.50
- Context
- 1.05M
At a glance
Quick verdict
How the two models stack up on the things people ask about most.
Lower price
GPT-6 Luna
7.4x cheaper for a typical chat
Higher intelligence score
Tie
Not enough benchmark data
Larger context window
GPT-6 Luna
1.05M vs 1M tokens
Newer release
Step 5 Preview
Released October 8, 2026
Benchmarks
Benchmark scores
Independent scores from Artificial Analysis. Higher is better.
Intelligence index
GPT-6 Luna38.1Coding index
GPT-6 LunaNot availableAgentic index
GPT-6 LunaNot availablePricing
Step 5 Preview vs GPT-6 Luna API pricing
Per-token API rates. Cheaper option highlighted.
| Metric | GPT-6 Luna | |
|---|---|---|
| Input tokensPer 1M tokens | $1 | $0.10 |
| Output tokensPer 1M tokens | $2.70 | $0.50 |
| Cached input (read)Per 1M tokens | $0.05 | $0.01 |
| Cache writePer 1M tokens | Not available | $0.13 |
| Long-context pricingPer 1M tokens, for very long prompts | Same rate at any length | $0.20 in / $0.75 out above 272K |
| Web searchPer request | Not available | $0.01 |
What it costs in practice
Estimated cost per 1,000 requests at standard rates. Coding and long-document figures also show the cost when the input is already cached.
Chat message
2K in, 500 out
GPT-6 Luna$0.45Coding task
30K in, 4K out
GPT-6 Luna$5$2.30 cachedLong document summary
150K in, 2K out
GPT-6 Luna$16$2.50 cachedSpecs
Context window and capabilities
How much each model can read, how much it can write, and what it accepts as input.
| Metric | GPT-6 Luna | |
|---|---|---|
| Context window | 1M tokens | 1.05M tokens |
| Max output | 64K tokens | 128K tokens |
| Input types | Image, Text, Video | File, Image, Text |
| Output types | Text | Text |
| Reasoning effort levels | High, Medium, Low | Max, Extra high, High, Medium, Low, None |
| Default reasoning effort | Medium | Medium |
| Release date | October 8, 2026 | September 22, 2026 |
Features
Supported features
API features available for each model.
| Metric | GPT-6 Luna | |
|---|---|---|
| Tool calling | Supported | Supported |
| Structured outputs | Supported | Supported |
| JSON mode | Supported | Supported |
| Reasoning | Supported | Supported |
| Temperature | Supported | Not supported |
| Stop sequences | Supported | Not supported |
| Deterministic seed | Not supported | Supported |
| Verbosity control | Not supported | Supported |
Keep exploring
More on these models
Other head-to-heads, the full model page, and the alternatives list for each model.
- Step 5 Preview vs DeepSeek V4.1 Flash
- Step 5 Preview vs GLM 5.3 Flash
- Step 5 Preview vs MiMo-V2.6-Flash
- Step 5 Preview vs Hy4 preview
- Step 5 Preview vs DeepSeek V4 Flash 0731
- Step 5 Preview vs Claude Opus 5.5
- Step 5 Preview vs GLM 5.3
- Step 5 Preview vs DeepSeek V4 Flash 0423
- Step 5 Preview vs Gemini 3.8 Flash
- Step 5 Preview vs Hy3
- Step 5 Preview vs DeepSeek V4 Pro 0813
- Step 5 Preview vs Gemini 3 Flash Preview
- Step 5 Preview vs Qwen3.8 27B
- Step 5 Preview vs Gemini 2.5 Flash
- Step 5 Preview vs Step 3.7 Flash
GPT-6 LunaView full model details- GPT-6 Luna vs DeepSeek V4.1 Flash
- GPT-6 Luna vs GLM 5.3 Flash
- GPT-6 Luna vs MiMo-V2.6-Flash
- GPT-6 Luna vs Hy4 preview
- GPT-6 Luna vs DeepSeek V4 Flash 0731
- GPT-6 Luna vs Claude Opus 5.5
- GPT-6 Luna vs GLM 5.3
- GPT-6 Luna vs DeepSeek V4 Flash 0423
- GPT-6 Luna vs Gemini 3.8 Flash
- GPT-6 Luna vs Hy3
- GPT-6 Luna vs GPT-5.6 Luna
- GPT-6 Luna vs GPT-6.1 Sol
- GPT-6 Luna vs Muse Spark 1.3 Contributor
- GPT-6 Luna vs Claude Sonnet 5.5
- GPT-6 Luna vs MiMo-V2.6-Pro
- GPT-6 Luna vs DeepSeek V4 Pro 0813
- GPT-6 Luna vs GPT-6 Astra
- GPT-6 Luna vs Claude Opus 5
- GPT-6 Luna vs Claude Fable 5.1
- GPT-6 Luna vs DeepSeek V4 Pro 0423
- GPT-6 Luna vs Solar Pro 4
- GPT-6 Luna vs GPT-6 Luna Pro
- GPT-6 Luna vs Claude Haiku 5.5
- GPT-6 Luna vs Ling 3.1 Flash
- GPT-6 Luna vs Qwen3.8 Flash
- GPT-6 Luna vs Qwen3.7 Flash
- GPT-6 Luna vs DeepSeek V4 Flash Vision Exp
- GPT-6 Luna vs GLM 5.3 FlashX
- GPT-6 Luna vs GPT-5.6 Luna Pro
Our take
GPT-6 Luna is 7.4x cheaper for a typical chat. GPT-6 Luna has the larger context window (1.05M vs 1M tokens). The right pick depends on your workload, so the quickest way to settle it is to send the same prompt to both and compare.
FAQ
Frequently asked questions
Is Step 5 Preview or GPT-6 Luna cheaper?
GPT-6 Luna is cheaper for a typical chat (2K input tokens and 500 output tokens). GPT-6 Luna costs $0.10 per 1M input tokens and $0.50 per 1M output tokens, while Step 5 Preview costs $1 per 1M input tokens and $2.70 per 1M output tokens.
Which has a bigger context window, Step 5 Preview or GPT-6 Luna?
GPT-6 Luna supports up to 1.05M tokens of context, compared with 1M for Step 5 Preview.
Can I use Step 5 Preview and GPT-6 Luna at the same time?
Yes. Shortcut Chat sends one prompt to multiple models at once, so you can see Step 5 Preview and GPT-6 Luna answer side by side and keep the better response.
Why choose? Ask both.
Send one prompt to Step 5 Preview and GPT-6 Luna at the same time. Compare the answers side by side and keep the best one.