> GPT-6.1 Sol vs Muse Spark 1.3: index scores 184 and 170 (GPT-4 = 100), API prices, context windows and results on the same independent tests, side by side.

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# Compare

Side by side on the same independent tests, with price and context. The link in your address bar shares this exact comparison.

[GPT-6.1 Sol](https://themodelindex.org/models/gpt-6-1-sol/)

[Muse Spark 1.3](https://themodelindex.org/models/muse-spark-1-3/)

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Next to GPT-6.1 Sol

Cheapest at this level

Claude Sonnet 5.5

Best open model, measured

Kimi K3

Closest rival, another lab

Gemini 4 Argon

The version it replaced

GPT-6 Sol

Where it started

GPT-4

Presets

Best open vs best closed (measured)

Today vs GPT-4 (2023)

Top three labs

US vs China, best of each

[GPT-6.1 Sol](https://themodelindex.org/models/gpt-6-1-sol/)

184

168–200

Weights

Closed

Released

Sep 2026

Price in / out

$2.0 / $10

Context

1.05M

Core tests taken

3 of 8

[Muse Spark 1.3](https://themodelindex.org/models/muse-spark-1-3/)

170

159–182

Weights

Closed

Released

Sep 2026

Price in / out

$1.25 / $4.25

Context

1.05M

Core tests taken

2 of 8

GPT-6.1 Sol leads Muse Spark 1.3 by 14 points, ahead on 2 of 2 shared core tests, at 2.0× the price.

## Test by test · independent results · Epoch AI

GPT-6.1 Sol

Muse Spark 1.3

_Chart: Test results for the selected models_

Only tests that at least two of these models have taken. Bold rows are the core tests shown on every profile; all of these results inform the index score. Task length (METR) is listed below the chart because it is a duration, not a percentage.

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Source: https://themodelindex.org/compare/gpt-6-1-sol-vs-muse-spark-1-3/ · The Model Index · data as of 2026-10-02