ZMIME
Comparison · 3 models · Updated Oct 4, 2026

Gemini 3.8 Flash vs GPT-6 Luna vs Muse Spark 1.3

GPT-6 Luna comes out ahead, 83 to 73 and 73 on our weighted score, and it is the cheaper option too.

  1. Google

    Gemini 3.8 Flash

    Released Sep 2, 2026

    73/100
    • ECI156.9
    • Price$0.75 / $3.75
    • Context1.05M
    Full specs Remove Gemini 3.8 Flash
  2. Our pick

    OpenAI

    GPT-6 Luna

    Released Sep 22, 2026

    83/100
    • ECI—
    • Price$0.10 / $0.50
    • Context1.05M
    Full specs Remove GPT-6 Luna

  3. Meta

    Muse Spark 1.3

    Released Sep 2, 2026

    73/100
    • ECI156.9
    • Price$1.25 / $4.25
    • Context1.05M
    Full specs Remove Muse Spark 1.3
01 — Verdict

GPT-6 Luna is our pick

GPT-6 Luna is the better all-round choice, scoring 83/100 against Muse Spark 1.3 (73) and Gemini 3.8 Flash (73). It leads on capability and price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%. Capability uses the average of shared benchmarks (FrontierMath Tiers 1–3 and OTIS Mock AIME 2024–2025), because GPT-6 Luna has no Capabilities Index score yet.

  • CapabilityGPT-6 LunaShared benchmarks: GPT-6 Luna 88.9% · Muse Spark 1.3 86.8% · Gemini 3.8 Flash 83.7%
  • Lowest priceGPT-6 LunaGPT-6 Luna $0.20 · Gemini 3.8 Flash $1.50 · Muse Spark 1.3 $2.00 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameGPT-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-6 Luna: Text, Images, PDFs · Muse Spark 1.3: Text, Images, PDFs, Audio, Video
  • Self-hostingNo open weightsAll three are available only through APIs
How the score is built
MeasureWeightGemini 3.8 FlashGPT-6 LunaMuse Spark 1.3
CapabilityShared benchmarks50%848987
Price25%428336
Inputs & features15%10080100
Context window10%616161
Overall100%73/10083/10073/100
02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

Gemini 3.8 Flash vs GPT-6 Luna vs Muse Spark 1.3 specifications side by side
SpecificationGemini 3.8 FlashGoogleGPT-6 LunaOpenAIMuse Spark 1.3Meta
Capability
Capabilities Index (ECI)156.9 (best)—156.9
ECI rank#15 of 148 (best)—#17 of 148
GPQA DiamondGraduate-level science questions95.4% (best)90.5%—
FrontierMath Tiers 1–3Research-level mathematics68.4%79.0% (best)74.4%
OTIS Mock AIME 2024–2025Competition mathematics98.9%98.9%99.2% (best)
SimpleQA VerifiedShort factual questions69.7% (best)41.4%—
Price per million tokens
Input$0.75$0.10 (best)$1.25
Output$3.75$0.50 (best)$4.25
Cached input$0.075$0.01 (best)$0.15
Blended (3:1)$1.50$0.20 (best)$2.00
Long-context rateSame rateOver 272K: $0.20 / $0.75Same rate
Price sourceOfficial Google APIOfficial OpenAI APIOfficial Meta API
Limits
Context window1,048,576 tokens1,050,000 tokens (best)1,048,576 tokens
Max output65,536 tokens128,000 tokens131,072 tokens (best)
Inputs and features
TextYesYesYes
ImagesYesYesYes
PDFsYesYesYes
AudioYesNoYes
VideoYesNoYes
ReasoningYeslow · medium · highYeslow · medium · high · xhigh · maxYesminimal · low · medium · high · xhigh · max
Tool callingYesYesYes
Structured outputYesYesYes
Availability
WeightsProprietaryProprietaryProprietary
API model IDgemini-3.8-flashgpt-6-lunamuse-spark-1.3
API providers2124 (best)12
ReleasedSep 2, 2026Sep 22, 2026Sep 2, 2026
Knowledge cutoff—May 18, 2026—
03 — Cost

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-6 Luna$2.00
  • Muse Spark 1.3$21.00
04 — Questions

Which should you choose?

Which is better: Gemini 3.8 Flash, GPT-6 Luna or Muse Spark 1.3?

GPT-6 Luna is the better all-round choice, scoring 83/100 against Muse Spark 1.3 (73) and Gemini 3.8 Flash (73). It leads on capability and price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%. Capability uses the average of shared benchmarks (FrontierMath Tiers 1–3 and OTIS Mock AIME 2024–2025), because GPT-6 Luna has no Capabilities Index score yet.

Which is cheaper, Gemini 3.8 Flash, GPT-6 Luna or Muse Spark 1.3?

GPT-6 Luna is cheaper at $0.10 input / $0.50 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 $0.20 per million tokens for GPT-6 Luna versus $1.50 for Gemini 3.8 Flash (7.5× as much) and $2.00 for Muse Spark 1.3 (10× as much).

Which scores higher on benchmarks?

Not every model here has a Capabilities Index score, so we compare the average of shared benchmarks (FrontierMath Tiers 1–3 and OTIS Mock AIME 2024–2025): GPT-6 Luna 88.9%, Muse Spark 1.3 86.8% and Gemini 3.8 Flash 83.7%. On individual benchmarks: FrontierMath Tiers 1–3 — GPT-6 Luna 79.0%, 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-6 Luna 98.9%.

Which is better for coding?

There are no published SWE-bench Verified results for Gemini 3.8 Flash, GPT-6 Luna and Muse Spark 1.3 yet, so there is no like-for-like coding score. On overall capability, GPT-6 Luna 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-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-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-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-6 Luna and Muse Spark 1.3 are proprietary and only available through APIs and apps.

Which is newer?

GPT-6 Luna is the newest, released Sep 22, 2026. Gemini 3.8 Flash came out Sep 2, 2026; Muse Spark 1.3 came out Sep 2, 2026. Knowledge cutoff: GPT-6 Luna May 18, 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.

05 — Keep comparing

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