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Comparison · 2 models · Updated Oct 4, 2026

GPT-5.6 Luna vs Muse Spark 1.3

GPT-5.6 Luna comes out ahead, 78 to 73 on our weighted score, and it is the cheaper option too.

  1. Our pick

    OpenAI

    GPT-5.6 Luna

    Released Jul 9, 2026

    78/100
    • ECI156.5
    • Price$0.20 / $1.20
    • Context1.05M
    Full specs Remove GPT-5.6 Luna

  2. 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

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

GPT-5.6 Luna is our pick

GPT-5.6 Luna is the better all-round choice, scoring 78/100 against Muse Spark 1.3 (73). It leads on price. Muse Spark 1.3 wins on inputs & features. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityMuse Spark 1.3Capabilities Index (ECI): Muse Spark 1.3 156.9 · GPT-5.6 Luna 156.5
  • Lowest priceGPT-5.6 LunaGPT-5.6 Luna $0.45 · Muse Spark 1.3 $2.00 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameGPT-5.6 Luna 1,050,000 · Muse Spark 1.3 1,048,576 tokens
  • Widest inputsMuse Spark 1.3GPT-5.6 Luna: Text, Images, PDFs · Muse Spark 1.3: Text, Images, PDFs, Audio, Video
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGPT-5.6 LunaMuse Spark 1.3
CapabilityCapabilities Index (ECI)50%8687
Price25%6636
Inputs & features15%80100
Context window10%6161
Overall100%78/10073/100
02 — Side by side

Every spec in one table

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

GPT-5.6 Luna vs Muse Spark 1.3 specifications side by side
SpecificationGPT-5.6 LunaOpenAIMuse Spark 1.3Meta
Capability
Capabilities Index (ECI)156.5156.9 (best)
ECI rank#21 of 148#17 of 148 (best)
GPQA DiamondGraduate-level science questions91.6%—
FrontierMath Tiers 1–3Research-level mathematics82.1% (best)74.4%
OTIS Mock AIME 2024–2025Competition mathematics98.3%99.2% (best)
SimpleQA VerifiedShort factual questions41.0%—
Price per million tokens
Input$0.20 (best)$1.25
Output$1.20 (best)$4.25
Cached input$0.02 (best)$0.15
Blended (3:1)$0.45 (best)$2.00
Long-context rateOver 272K: $0.40 / $1.80Same rate
Price sourceOfficial OpenAI APIOfficial Meta API
Limits
Context window1,050,000 tokens (best)1,048,576 tokens
Max output128,000 tokens131,072 tokens (best)
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoYes
VideoNoYes
ReasoningYeslow · medium · high · xhigh · maxYesminimal · low · medium · high · xhigh · max
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDgpt-5.6-lunamuse-spark-1.3
API providers38 (best)12
ReleasedJul 9, 2026Sep 2, 2026
Knowledge cutoffFeb 16, 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.

  • GPT-5.6 Luna$4.40
  • Muse Spark 1.3$21.00
04 — Questions

Which should you choose?

Which is better: GPT-5.6 Luna or Muse Spark 1.3?

GPT-5.6 Luna is the better all-round choice, scoring 78/100 against Muse Spark 1.3 (73). It leads on price. Muse Spark 1.3 wins on inputs & features. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, 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). 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 $2.00 for Muse Spark 1.3 (4.4× as much).

Which scores higher on benchmarks?

Muse Spark 1.3 scores higher on the Capabilities Index (ECI): 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 (154.7–159.6 vs 154.1–158.6), 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%; OTIS Mock AIME 2024–2025 — Muse Spark 1.3 99.2%, GPT-5.6 Luna 98.3%.

Which is better for coding?

There are no published SWE-bench Verified results for GPT-5.6 Luna and Muse Spark 1.3 yet, so there is no like-for-like coding score. On overall capability, Muse Spark 1.3 leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

Their context windows are effectively the same size: GPT-5.6 Luna 1,050,000 and Muse Spark 1.3 1,048,576 tokens. Maximum output per response: 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?

GPT-5.6 Luna accepts text, images and PDFs; Muse Spark 1.3 accepts text, images, PDFs, audio and video. Muse Spark 1.3 handles the widest range of inputs.

Are any of these open source?

No. GPT-5.6 Luna and Muse Spark 1.3 are proprietary and only available through APIs and apps.

Which is newer?

Muse Spark 1.3 is the newest, released 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.

05 — Keep comparing

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