AI model comparison
GLM 5.3 FlashX vs GPT-5.6 Luna
Pricing, context window, benchmarks, and features compared side by side. Or skip the guesswork and send one prompt to both.
Z.ai
GLM 5.3 FlashX
GLM-5.3-FlashX is the high-speed variant of Z.ai's GLM-5.3-Flash, a native multimodal model delivering inference speeds of up to 200 tokens/s.
- Input / 1M
- $0.37
- Output / 1M
- $1.25
- Context
- 1.05M
OpenAI
GPT-5.6 Luna
GPT-5.6 Luna is a fast, cost-efficient model in OpenAI's GPT-5.6 series.
- Input / 1M
- $0.20
- Output / 1M
- $1.20
- Context
- 1.05M
At a glance
Quick verdict
How the two models stack up on the things people ask about most.
Lower price
GPT-5.6 Luna
1.4x cheaper for a typical chat
Higher intelligence score
Tie
Not enough benchmark data
Larger context window
GPT-5.6 Luna
1.05M vs 1.05M tokens
Newer release
GLM 5.3 FlashX
Released September 18, 2026
Benchmarks
Benchmark scores
Independent scores from Artificial Analysis. Higher is better.
Intelligence index
GPT-5.6 Luna37.3Coding index
GPT-5.6 Luna71.4Agentic index
GPT-5.6 Luna42.1Pricing
GLM 5.3 FlashX vs GPT-5.6 Luna API pricing
Per-token API rates. Cheaper option highlighted.
| Metric | GPT-5.6 Luna | |
|---|---|---|
| Input tokensPer 1M tokens | $0.37 | $0.20 |
| Output tokensPer 1M tokens | $1.25 | $1.20 |
| Cached input (read)Per 1M tokens | $0.09 | $0.02 |
| Cache writePer 1M tokens | Not available | $0.25 |
| Long-context pricingPer 1M tokens, for very long prompts | Same rate at any length | $0.40 in / $1.80 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-5.6 Luna$1Coding task
30K in, 4K out
GPT-5.6 Luna$10.80$5.40 cachedLong document summary
150K in, 2K out
GPT-5.6 Luna$32.40$5.40 cachedSpecs
Context window and capabilities
How much each model can read, how much it can write, and what it accepts as input.
| Metric | GPT-5.6 Luna | |
|---|---|---|
| Context window | 1.05M tokens | 1.05M tokens |
| Max output | 131K tokens | 128K tokens |
| Input types | Image, Text, Video | File, Image, Text |
| Output types | Text | Text |
| Reasoning effort levels | Max, High, Low | Max, Extra high, High, Medium, Low, None |
| Default reasoning effort | Max | Medium |
| Release date | September 18, 2026 | July 9, 2026 |
Features
Supported features
API features available for each model.
| Metric | GPT-5.6 Luna | |
|---|---|---|
| Tool calling | Supported | Supported |
| Structured outputs | Not supported | Supported |
| JSON mode | Supported | Supported |
| Reasoning | Supported | Supported |
| Temperature | Supported | Not supported |
| Stop sequences | Not 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.
GPT-5.6 LunaView full model details- GPT-5.6 Luna vs DeepSeek V4.1 Flash
- GPT-5.6 Luna vs GLM 5.3 Flash
- GPT-5.6 Luna vs MiMo-V2.6-Flash
- GPT-5.6 Luna vs Hy4 preview
- GPT-5.6 Luna vs GPT-6 Luna
- GPT-5.6 Luna vs DeepSeek V4 Flash 0731
- GPT-5.6 Luna vs Gemini 3.8 Flash
- GPT-5.6 Luna vs DeepSeek V4 Pro 0813
- GPT-5.6 Luna vs Claude Haiku 5.5
- GPT-5.6 Luna vs GPT-6 Luna Pro
- GPT-5.6 Luna vs Qwen3.8 27B
- GPT-5.6 Luna vs Gemini 3.7 Flash
- GPT-5.6 Luna vs Muse Spark 1.2
- GPT-5.6 Luna vs GPT-5.5
- GPT-5.6 Luna vs DeepSeek V4 Flash Vision Exp
- GPT-5.6 Luna vs Muse Spark 1.1
- GPT-5.6 Luna vs GPT-5.6 Luna Pro
Our take
GPT-5.6 Luna is 1.4x cheaper for a typical chat. GPT-5.6 Luna has the larger context window (1.05M vs 1.05M 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 GLM 5.3 FlashX or GPT-5.6 Luna cheaper?
GPT-5.6 Luna is cheaper for a typical chat (2K input tokens and 500 output tokens). GPT-5.6 Luna costs $0.20 per 1M input tokens and $1.20 per 1M output tokens, while GLM 5.3 FlashX costs $0.37 per 1M input tokens and $1.25 per 1M output tokens.
Which has a bigger context window, GLM 5.3 FlashX or GPT-5.6 Luna?
GPT-5.6 Luna supports up to 1.05M tokens of context, compared with 1.05M for GLM 5.3 FlashX.
Can I use GLM 5.3 FlashX and GPT-5.6 Luna at the same time?
Yes. Shortcut Chat sends one prompt to multiple models at once, so you can see GLM 5.3 FlashX and GPT-5.6 Luna answer side by side and keep the better response.
Why choose? Ask both.
Send one prompt to GLM 5.3 FlashX and GPT-5.6 Luna at the same time. Compare the answers side by side and keep the best one.