Gemini 3.8 Flash vs GPT-5.6 Luna vs Muse Spark 1.3
Too close to call on our weighted score (GPT-5.6 Luna 78, Gemini 3.8 Flash 75, Muse Spark 1.3 73). The right pick depends on what you value most.
GoogleGemini 3.8 Flash
75/100- ECI156.9
- Price$0.75 / $3.75
- Context1.05M
OpenAIGPT-5.6 Luna
78/100- ECI156.5
- Price$0.20 / $1.20
- Context1.05M
MetaMuse Spark 1.3
73/100- ECI156.9
- Price$1.25 / $4.25
- Context1.05M
Too close to call
It is close. Our weighted score puts them within 3 points (GPT-5.6 Luna 78/100, Gemini 3.8 Flash 75/100, Muse Spark 1.3 73/100), so choose by what matters most for your work: Gemini 3.8 Flash for raw capability and GPT-5.6 Luna on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGemini 3.8 FlashCapabilities Index (ECI): Gemini 3.8 Flash 156.9 · Muse Spark 1.3 156.9 · GPT-5.6 Luna 156.5
- Lowest priceGPT-5.6 LunaGPT-5.6 Luna $0.45 · Gemini 3.8 Flash $1.50 · Muse Spark 1.3 $2.00 per 1M tokens (3:1 blend)
- Longest contextAbout the sameGPT-5.6 Luna 1,050,000 · Gemini 3.8 Flash 1,048,576 · Muse Spark 1.3 1,048,576 tokens
- Widest inputsGemini 3.8 Flash and Muse Spark 1.3Gemini 3.8 Flash: Text, Images, PDFs, Audio, Video · GPT-5.6 Luna: Text, Images, PDFs · Muse Spark 1.3: Text, Images, PDFs, Audio, Video
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Gemini 3.8 Flash | GPT-5.6 Luna | Muse Spark 1.3 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 87 | 86 | 87 |
| Price | 25% | 42 | 66 | 36 |
| Inputs & features | 15% | 100 | 80 | 100 |
| Context window | 10% | 61 | 61 | 61 |
| Overall | 100% | 75/100 | 78/100 | 73/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Gemini 3.8 FlashGoogle | GPT-5.6 LunaOpenAI | Muse Spark 1.3Meta |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 156.9 (best) | 156.5 | 156.9 |
| ECI rank | #15 of 148 (best) | #21 of 148 | #17 of 148 |
| GPQA DiamondGraduate-level science questions | 95.4% (best) | 91.6% | — |
| FrontierMath Tiers 1–3Research-level mathematics | 68.4% | 82.1% (best) | 74.4% |
| OTIS Mock AIME 2024–2025Competition mathematics | 98.9% | 98.3% | 99.2% (best) |
| SimpleQA VerifiedShort factual questions | 69.7% (best) | 41.0% | — |
| Price per million tokens | |||
| Input | $0.75 | $0.20 (best) | $1.25 |
| Output | $3.75 | $1.20 (best) | $4.25 |
| Cached input | $0.075 | $0.02 (best) | $0.15 |
| Blended (3:1) | $1.50 | $0.45 (best) | $2.00 |
| Long-context rate | Same rate | Over 272K: $0.40 / $1.80 | Same rate |
| Price source | Official Google API | Official OpenAI API | Official Meta API |
| Limits | |||
| Context window | 1,048,576 tokens | 1,050,000 tokens (best) | 1,048,576 tokens |
| Max output | 65,536 tokens | 128,000 tokens | 131,072 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | Yes | No | Yes |
| Video | Yes | No | Yes |
| Reasoning | Yeslow · medium · high | Yeslow · medium · high · xhigh · max | Yesminimal · low · medium · high · xhigh · max |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gemini-3.8-flash | gpt-5.6-luna | muse-spark-1.3 |
| API providers | 21 | 38 (best) | 12 |
| Released | Sep 2, 2026 | Jul 9, 2026 | Sep 2, 2026 |
| Knowledge cutoff | — | Feb 16, 2026 | — |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Gemini 3.8 Flash$15.00
- GPT-5.6 Luna$4.40
- Muse Spark 1.3$21.00
Which should you choose?
Which is better: Gemini 3.8 Flash, GPT-5.6 Luna or Muse Spark 1.3?
It is close. Our weighted score puts them within 3 points (GPT-5.6 Luna 78/100, Gemini 3.8 Flash 75/100, Muse Spark 1.3 73/100), so choose by what matters most for your work: Gemini 3.8 Flash for raw capability and GPT-5.6 Luna on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Gemini 3.8 Flash, GPT-5.6 Luna or Muse Spark 1.3?
GPT-5.6 Luna is cheaper at $0.20 input / $1.20 output per million tokens (official OpenAI API price). Gemini 3.8 Flash costs $0.75 input / $3.75 output per million tokens (official Google API price); Muse Spark 1.3 costs $1.25 input / $4.25 output per million tokens (official Meta API price). At a typical mix of three input tokens to one output token, that is $0.45 per million tokens for GPT-5.6 Luna versus $1.50 for Gemini 3.8 Flash (3.3× as much) and $2.00 for Muse Spark 1.3 (4.4× as much).
Which scores higher on benchmarks?
Gemini 3.8 Flash scores higher on the Capabilities Index (ECI): Gemini 3.8 Flash 156.9 (#15 of 148), Muse Spark 1.3 156.9 (#17 of 148) and GPT-5.6 Luna 156.5 (#21 of 148). The confidence ranges of the top two overlap (154.6–160.4 vs 154.7–159.6), so treat the gap as small. On individual benchmarks: FrontierMath Tiers 1–3 — GPT-5.6 Luna 82.1%, Muse Spark 1.3 74.4%, Gemini 3.8 Flash 68.4%; OTIS Mock AIME 2024–2025 — Muse Spark 1.3 99.2%, Gemini 3.8 Flash 98.9%, GPT-5.6 Luna 98.3%.
Which is better for coding?
There are no published SWE-bench Verified results for Gemini 3.8 Flash, GPT-5.6 Luna and Muse Spark 1.3 yet, so there is no like-for-like coding score. On overall capability, Gemini 3.8 Flash leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.
Which has the bigger context window?
Their context windows are effectively the same size: Gemini 3.8 Flash 1,048,576, GPT-5.6 Luna 1,050,000 and Muse Spark 1.3 1,048,576 tokens. Maximum output per response: Gemini 3.8 Flash up to 65,536, GPT-5.6 Luna up to 128,000, Muse Spark 1.3 up to 131,072 tokens.
Which can read images, PDFs, audio or video?
Gemini 3.8 Flash accepts text, images, PDFs, audio and video; GPT-5.6 Luna accepts text, images and PDFs; Muse Spark 1.3 accepts text, images, PDFs, audio and video. Gemini 3.8 Flash handles the widest range of inputs.
Are any of these open source?
No. Gemini 3.8 Flash, GPT-5.6 Luna and Muse Spark 1.3 are proprietary and only available through APIs and apps.
Which is newer?
Gemini 3.8 Flash is the newest, released Sep 2, 2026. Muse Spark 1.3 came out Sep 2, 2026; GPT-5.6 Luna came out Jul 9, 2026. Knowledge cutoff: GPT-5.6 Luna Feb 16, 2026.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
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