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Comparison · 2 models · Updated Nov 2, 2026

GPT-5.6 Terra vs Muse Spark Open

Too close to call on our weighted score (Muse Spark Open 68, GPT-5.6 Terra 67). The right pick depends on what you value most.

  1. OpenAI

    GPT-5.6 Terra

    Released Jul 9, 2026

    67/100
    • ECI160.1
    • Price$2.00 / $12.00
    • Context1.05M
    Full specs Remove GPT-5.6 Terra

  2. Meta

    Muse Spark Open

    Released Oct 15, 2026New

    68/100
    • ECI155.1
    • Price$1.25 / $4.25
    • Context1.05M
    Full specs Remove Muse Spark Open

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01 — Verdict

Too close to call

It is close. Our weighted score puts them within a point (Muse Spark Open 68/100, GPT-5.6 Terra 67/100), so choose by what matters most for your work: GPT-5.6 Terra for raw capability and Muse Spark Open on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGPT-5.6 TerraCapabilities Index (ECI): GPT-5.6 Terra 160.1 · Muse Spark Open 155.1
  • Lowest priceMuse Spark OpenMuse Spark Open $2.00 · GPT-5.6 Terra $4.50 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameGPT-5.6 Terra 1,050,000 · Muse Spark Open 1,048,576 tokens
  • Widest inputsMuse Spark OpenGPT-5.6 Terra: Text, Images, PDFs · Muse Spark Open: Text, Images, Audio, Video
  • Self-hostingMuse Spark OpenPublishes downloadable weights (Muse Model License)
How the score is built
MeasureWeightGPT-5.6 TerraMuse Spark Open
CapabilityCapabilities Index (ECI)50%8983
Price25%1834
Inputs & features15%8080
Context window10%6161
Overall100%67/10068/100
02 — Side by side

Every spec in one table

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

GPT-5.6 Terra vs Muse Spark Open specifications side by side
SpecificationGPT-5.6 TerraOpenAIMuse Spark OpenMeta
Capability
Capabilities Index (ECI)160.1 (best)155.1
ECI rank#15 of 165 (best)#39 of 165
GPQA DiamondGraduate-level science questions93.3% (best)88.6%
FrontierMath Tiers 1–3Research-level mathematics86.0% (best)69.8%
OTIS Mock AIME 2024–2025Competition mathematics99.7% (best)98.1%
SimpleQA VerifiedShort factual questions43.2%56.6% (best)
Price per million tokens
Input$2.00$1.25 (best)
Output$12.00$4.25 (best)
Cached input$0.20—
Blended (3:1)$4.50$2.00 (best)
Long-context rateOver 272K: $4.00 / $18.00Same rate
Price sourceOfficial OpenAI APIMedian of 16 providers
Limits
Context window1,050,000 tokens (best)1,048,576 tokens
Max output128,000 tokens131,072 tokens (best)
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesNo
AudioNoYes
VideoNoYes
ReasoningYeslow · medium · high · xhigh · maxYes
Tool callingYesYes
Structured outputYesNo
Availability
WeightsProprietaryOpenMuse Model License
API model IDgpt-5.6-terra—
API providers45 (best)16
ReleasedJul 9, 2026Oct 15, 2026
Knowledge cutoffFeb 16, 2026Jan 4, 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 Terra$44.00
  • Muse Spark Open$21.00
04 — Questions

Which should you choose?

Which is better: GPT-5.6 Terra or Muse Spark Open?

It is close. Our weighted score puts them within a point (Muse Spark Open 68/100, GPT-5.6 Terra 67/100), so choose by what matters most for your work: GPT-5.6 Terra for raw capability and Muse Spark Open on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, GPT-5.6 Terra or Muse Spark Open?

Muse Spark Open is cheaper at $1.25 input / $4.25 output per million tokens (median across 16 API providers). GPT-5.6 Terra costs $2.00 input / $12.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $2.00 per million tokens for Muse Spark Open versus $4.50 for GPT-5.6 Terra (2.3× as much).

Which scores higher on benchmarks?

GPT-5.6 Terra scores higher on the Capabilities Index (ECI): GPT-5.6 Terra 160.1 (#15 of 165) and Muse Spark Open 155.1 (#39 of 165). Their confidence ranges do not overlap (157.8–163.4 vs 153.1–157.3), so the gap is a real one. On individual benchmarks: GPQA Diamond — GPT-5.6 Terra 93.3%, Muse Spark Open 88.6%; FrontierMath Tiers 1–3 — GPT-5.6 Terra 86.0%, Muse Spark Open 69.8%; OTIS Mock AIME 2024–2025 — GPT-5.6 Terra 99.7%, Muse Spark Open 98.1%; SimpleQA Verified — Muse Spark Open 56.6%, GPT-5.6 Terra 43.2%.

Which is better for coding?

There are no published SWE-bench Verified results for GPT-5.6 Terra and Muse Spark Open yet, so there is no like-for-like coding score. On overall capability, GPT-5.6 Terra 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 Terra 1,050,000 and Muse Spark Open 1,048,576 tokens. Maximum output per response: GPT-5.6 Terra up to 128,000, Muse Spark Open up to 131,072 tokens.

Which can read images, PDFs, audio or video?

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

Are any of these open source?

Muse Spark Open publishes its weights (Muse Model License) and can be self-hosted; GPT-5.6 Terra is proprietary.

Which is newer?

Muse Spark Open is the newest, released Oct 15, 2026. GPT-5.6 Terra came out Jul 9, 2026. Knowledge cutoff: GPT-5.6 Terra Feb 16, 2026, Muse Spark Open Jan 4, 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 Nov 2, 2026.

05 — Keep comparing

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