Muse Spark 1.3 high vs Opus 4.8 medium

No clear quality winner: Opus 4.8 medium won 11, Muse Spark 1.3 high won 7, 6 tied; Muse Spark 1.3 high leads on cost and agent time: 70.4× cheaper and 1.8× faster.

24 tasksData from October 29, 2026

Stet score

Muse Spark 1.3 highmuse · high reasoningRank 14 of 16

31.995% range 23.5–40.6

Opus 4.8 mediumclaude-code · medium reasoningRank 12 of 16

39.295% range 29.0–49.77.3 points higher

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

GPT 6 Luna max

47.4

DeepSeek V4.1 Flash max

45.9

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

Muse Spark 1.3 high$0.1070.4× cheaper

Opus 4.8 medium$7.05

Agent time / task

Muse Spark 1.3 high13.2 min1.8× faster

Opus 4.8 medium23.3 min

Quality

Head-to-head matchups

Muse Spark 1.3 high won7

Tied6

Opus 4.8 medium won11

Opus 4.8 medium’s win share 60%, 95% range 43–76%Ties are within judge noise.

Task by task

Muse Spark 1.3 high solved 1 task that Opus 4.8 medium didn’t, and Opus 4.8 medium solved 4 that Muse Spark 1.3 high didn’t. Both solved 9; neither solved 10.

Muse Spark 1.3 high only 1

stet-2450ca2dEquivalent to the merged fix

Opus 4.8 medium only 4

stet-15439c21Passed tests
stet-commit-f0caded9Equivalent to the merged fix
stet-6f84e978Passed tests
stet-commit-60a0e6c2Passed tests

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	Muse Spark 1.3 high	Opus 4.8 medium	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`	Failed	Passed tests	Opus 4.8 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	Equivalent to the merged fix	Opus 4.8 medium only
`stet-6f84e978`	Failed	Passed tests	Opus 4.8 medium only
`stet-2450ca2d`	Equivalent to the merged fix	Failed	Muse Spark 1.3 high only
`stet-commit-342d0ac0`	Failed	Failed	Neither
`stet-commit-f8ae1177`	Failed	Failed	Neither
`stet-commit-60a0e6c2`	Failed	Passed tests	Opus 4.8 medium only
`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	Muse Spark 1.3 high	Opus 4.8 medium
Harness	muse	claude-code
Reasoning effort	high	medium
Rank	14 of 16	12 of 16
Stet score	31.995% range 23.5–40.6	39.295% range 29.0–49.7
Solved	10/248 passed, 2 judged equivalent	13/2411 passed, 2 judged equivalent
Cost / task	$0.10	$7.05
Agent time / task	13.2 min	23.3 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