GPT 6 Luna max vs Muse Spark 1.3 high

No clear quality winner: GPT 6 Luna max won 14, Muse Spark 1.3 high won 4, 6 tied; Muse Spark 1.3 high leads on cost and agent time: 3.7× cheaper and 4.5× faster.

24 tasksData from October 29, 2026

Stet score

GPT 6 Luna maxcodex · max reasoningRank 10 of 16

47.495% range 38.0–56.415.5 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

GPT 6.1 Sol medium

62.5

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

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

A directional read: their 95% score ranges overlap.

Cost / task

GPT 6 Luna max$0.37

Muse Spark 1.3 high$0.103.7× cheaper

Agent time / task

GPT 6 Luna max59.7 min

Muse Spark 1.3 high13.2 min4.5× faster

Quality

Head-to-head matchups

GPT 6 Luna max won14

Tied6

Muse Spark 1.3 high won4

GPT 6 Luna max’s win share 67%, 95% range 51–82%Ties are within judge noise.

Task by task

GPT 6 Luna max solved 3 tasks that Muse Spark 1.3 high didn’t, and Muse Spark 1.3 high solved 1 that GPT 6 Luna max didn’t. Both solved 9; neither solved 11.

GPT 6 Luna max only 3

stet-commit-f0caded9Equivalent 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 Luna max	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`	Equivalent to the merged fix	Passed tests	Both
`stet-15439c21`	Failed	Failed	Neither
`stet-commit-5d766dde`	Equivalent to the merged fix	Equivalent to the merged fix	Both
`stet-43493c52`	Passed tests	Passed tests	Both
`stet-commit-f0caded9`	Equivalent to the merged fix	Failed	GPT 6 Luna max only
`stet-6f84e978`	Failed	Failed	Neither
`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 Luna max only
`stet-commit-f8ae1177`	Passed tests	Failed	GPT 6 Luna max 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 Luna max	Muse Spark 1.3 high
Harness	codex	muse
Reasoning effort	max	high
Rank	10 of 16	14 of 16
Stet score	47.495% range 38.0–56.4	31.995% range 23.5–40.6
Solved	12/248 passed, 4 judged equivalent	10/248 passed, 2 judged equivalent
Cost / task	$0.37	$0.10
Agent time / task	59.7 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