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Opus 4.8 medium vs Pareto 26.9 medium

No clear quality winner: Pareto 26.9 medium won 13, Opus 4.8 medium won 7, 4 tied; Opus 4.8 medium leads on cost and agent time: 1.8× cheaper and 1.7× faster.

24 tasksData from

Stet score

Opus 4.8 mediumclaude-code · medium reasoningRank 12 of 16

39.295% range 29.0–49.7

Pareto 26.9 mediumclaude-code · medium reasoningRank 7 of 16

57.195% range 47.0–66.717.9 points higher

A directional read: their 95% score ranges overlap.

Cost / task

Opus 4.8 medium$7.051.8× cheaper
Pareto 26.9 medium$12.47

Agent time / task

Opus 4.8 medium23.3 min1.7× faster
Pareto 26.9 medium39.2 min

Quality

Head-to-head matchups

Opus 4.8 medium won7

Tied4

Pareto 26.9 medium won13

Pareto 26.9 medium’s win share 61%, 95% range 43–77%Ties are within judge noise.

Task by task

Opus 4.8 medium solved 2 tasks that Pareto 26.9 medium didn’t, and Pareto 26.9 medium solved 2 that Opus 4.8 medium didn’t. Both solved 11; neither solved 9.

Opus 4.8 medium only 2

  • stet-commit-5d766ddeEquivalent to the merged fix
  • stet-commit-60a0e6c2Passed tests

Pareto 26.9 medium only 2

  • stet-2450ca2dPassed tests
  • stet-commit-f8ae1177Passed 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
TaskOpus 4.8 mediumPareto 26.9 mediumSolved by
stet-3169aefaPassed testsPassed testsBoth
stet-89dfbc27Passed testsPassed testsBoth
stet-b28f4fe7Passed testsPassed testsBoth
stet-232b50baPassed testsPassed testsBoth
stet-5276aa3fPassed testsPassed testsBoth
stet-commit-bbbbae09Passed testsPassed testsBoth
stet-66762b4cPassed testsPassed testsBoth
stet-15439c21Passed testsPassed testsBoth
stet-commit-5d766ddeEquivalent to the merged fixFailedOpus 4.8 medium only
stet-43493c52Passed testsPassed testsBoth
stet-commit-f0caded9Equivalent to the merged fixEquivalent to the merged fixBoth
stet-6f84e978Passed testsPassed testsBoth
stet-2450ca2dFailedPassed testsPareto 26.9 medium only
stet-commit-342d0ac0FailedFailedNeither
stet-commit-f8ae1177FailedPassed testsPareto 26.9 medium only
stet-commit-60a0e6c2Passed testsFailedOpus 4.8 medium only
stet-commit-5e075641FailedFailedNeither
stet-commit-2826765eFailedFailedNeither
stet-commit-a8716b88FailedFailedNeither
stet-commit-e928166fFailedFailedNeither
stet-commit-30506f8eFailedFailedNeither
stet-commit-87814583FailedFailedNeither
stet-commit-d2ab0c25FailedFailedNeither
stet-commit-e41c2e2dFailedFailedNeither

Side by side

Side by side
MetricOpus 4.8 mediumPareto 26.9 medium
Harnessclaude-codeclaude-code
Reasoning effortmediummedium
Rank12 of 167 of 16
Stet score39.295% range 29.0–49.757.195% range 47.0–66.7
Solved13/2411 passed, 2 judged equivalent13/2412 passed, 1 judged equivalent
Cost / task$7.05$12.47
Agent time / task23.3 min39.2 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 .
  • Both setups come from the same leaderboard run of 16 setups: bmk_d4ba310fdf50db4ccb2092e3.

See all 16 setups on the leaderboardHow Stet measures