GPT 6.1 Sol medium vs Muse Spark 1.3 high

No clear quality winner: GPT 6.1 Sol medium won 17, Muse Spark 1.3 high won 2, 5 tied; Muse Spark 1.3 high leads on cost: 11.0× cheaper; GPT 6.1 Sol medium leads on agent time: 1.1× faster.

24 tasksData from October 29, 2026

Stet score

GPT 6.1 Sol mediumcodex · medium reasoningRank 4 of 16

62.595% range 53.0–71.730.6 points higher

Muse Spark 1.3 highmuse · high reasoningRank 14 of 16

31.995% range 23.5–40.6

Other setups

Muse Wonder Full low

70.4

GPT 5.6 Luna max

70.3

SWE-2 Max high

64.3

Opus 5 medium

62.3

Grok 4.7 high

60.7

Pareto 26.9 medium

57.1

Haiku 5.5 max

55.5

GPT 6 Sol medium

55.4

GPT 6 Luna max

47.4

DeepSeek V4.1 Flash max

45.9

Opus 4.8 medium

39.2

Haiku 5.5 low

38.9

GLM 5.3 Flash high

29.0

GPT 6 Luna low

19.9

Their 95% score ranges don’t overlap.

Cost / task

GPT 6.1 Sol medium$1.10

Muse Spark 1.3 high$0.1011.0× cheaper

Agent time / task

GPT 6.1 Sol medium11.8 min1.1× faster

Muse Spark 1.3 high13.2 min

Quality

Head-to-head matchups

GPT 6.1 Sol medium won17

Tied5

Muse Spark 1.3 high won2

GPT 6.1 Sol medium’s win share 78%, 95% range 64–91%Ties are within judge noise.

Task by task

GPT 6.1 Sol medium solved 4 tasks that Muse Spark 1.3 high didn’t, and Muse Spark 1.3 high solved 1 that GPT 6.1 Sol medium didn’t. Both solved 9; neither solved 10.

GPT 6.1 Sol medium only 4

stet-15439c21Passed tests
stet-6f84e978Equivalent to the merged fix
stet-commit-342d0ac0Equivalent to the merged fix
stet-commit-f8ae1177Passed tests

Muse Spark 1.3 high only 1

stet-2450ca2dEquivalent to the merged fix

A task counts as solved when its tests passed or a judge found the fix equivalent to the merged change, as in the leaderboard’s Solved column. Stet score also weighs code quality, so it can order the two differently.

All 24 compared tasks

Task by task
Task	GPT 6.1 Sol medium	Muse Spark 1.3 high	Solved by
`stet-3169aefa`	Passed tests	Passed tests	Both
`stet-89dfbc27`	Passed tests	Passed tests	Both
`stet-b28f4fe7`	Passed tests	Passed tests	Both
`stet-232b50ba`	Passed tests	Passed tests	Both
`stet-5276aa3f`	Passed tests	Passed tests	Both
`stet-commit-bbbbae09`	Passed tests	Passed tests	Both
`stet-66762b4c`	Passed tests	Passed tests	Both
`stet-15439c21`	Passed tests	Failed	GPT 6.1 Sol medium only
`stet-commit-5d766dde`	Equivalent to the merged fix	Equivalent to the merged fix	Both
`stet-43493c52`	Passed tests	Passed tests	Both
`stet-commit-f0caded9`	Failed	Failed	Neither
`stet-6f84e978`	Equivalent to the merged fix	Failed	GPT 6.1 Sol medium only
`stet-2450ca2d`	Failed	Equivalent to the merged fix	Muse Spark 1.3 high only
`stet-commit-342d0ac0`	Equivalent to the merged fix	Failed	GPT 6.1 Sol medium only
`stet-commit-f8ae1177`	Passed tests	Failed	GPT 6.1 Sol medium only
`stet-commit-60a0e6c2`	Failed	Failed	Neither
`stet-commit-5e075641`	Failed	Failed	Neither
`stet-commit-2826765e`	Failed	Failed	Neither
`stet-commit-a8716b88`	Failed	Failed	Neither
`stet-commit-e928166f`	Failed	Failed	Neither
`stet-commit-30506f8e`	Failed	Failed	Neither
`stet-commit-87814583`	Failed	Failed	Neither
`stet-commit-d2ab0c25`	Failed	Failed	Neither
`stet-commit-e41c2e2d`	Failed	Failed	Neither

Side by side

Side by side
Metric	GPT 6.1 Sol medium	Muse Spark 1.3 high
Harness	codex	muse
Reasoning effort	medium	high
Rank	4 of 16	14 of 16
Stet score	62.595% range 53.0–71.7	31.995% range 23.5–40.6
Solved	13/2410 passed, 3 judged equivalent	10/248 passed, 2 judged equivalent
Cost / task	$1.10	$0.10
Agent time / task	11.8 min	13.2 min

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About this data

24 tasks, each a merged change replayed from the repo as it was just before the merge.
Data from October 29, 2026.
Both setups come from the same leaderboard run of 16 setups: bmk_d4ba310fdf50db4ccb2092e3.

See all 16 setups on the leaderboard How Stet measures