Skip to the comparison
STET
Join the waitlist

Opus 5 medium vs Pareto 26.9 medium

No clear quality winner: Opus 5 medium won 10, Pareto 26.9 medium won 8, 6 tied; Opus 5 medium leads on cost and agent time: 1.8× cheaper and 1.7× faster.

24 tasksData from

Stet score

Opus 5 mediummedium reasoningRank 4 of 15

63.795% range 53.3–73.65.3 points higher

Pareto 26.9 mediumclaude-code · medium reasoningRank 6 of 15

58.495% range 48.1–68.2

A directional read: their 95% score ranges overlap.

Cost / task

Opus 5 medium$6.781.8× cheaper
Pareto 26.9 medium$12.47

Agent time / task

Opus 5 medium23.2 min1.7× faster
Pareto 26.9 medium39.2 min

Quality

Head-to-head matchups

Opus 5 medium won10

Tied6

Pareto 26.9 medium won8

Opus 5 medium’s win share 53%, 95% range 36–70%Ties are within judge noise.

Task by task

Opus 5 medium solved 2 tasks that Pareto 26.9 medium didn’t, and Pareto 26.9 medium solved 1 that Opus 5 medium didn’t. Both solved 12; neither solved 9.

Opus 5 medium only 2

  • stet-commit-5d766ddeEquivalent to the merged fix
  • stet-commit-2826765eEquivalent to the merged fix

Pareto 26.9 medium only 1

  • 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 5 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-15439c21Passed testsPassed testsBoth
stet-66762b4cPassed testsPassed testsBoth
stet-commit-5d766ddeEquivalent to the merged fixFailedOpus 5 medium only
stet-commit-f0caded9Passed testsEquivalent to the merged fixBoth
stet-43493c52Passed testsPassed testsBoth
stet-6f84e978Passed testsPassed testsBoth
stet-2450ca2dPassed testsPassed testsBoth
stet-commit-f8ae1177FailedPassed testsPareto 26.9 medium only
stet-commit-342d0ac0FailedFailedNeither
stet-commit-60a0e6c2FailedFailedNeither
stet-commit-5e075641FailedFailedNeither
stet-commit-2826765eEquivalent to the merged fixFailedOpus 5 medium only
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 5 mediumPareto 26.9 medium
Harness—claude-code
Reasoning effortmediummedium
Rank4 of 156 of 15
Stet score63.795% range 53.3–73.658.495% range 48.1–68.2
Solved14/2412 passed, 2 judged equivalent13/2412 passed, 1 judged equivalent
Cost / task$6.78$12.47
Agent time / task23.2 min39.2 min

See which setup wins on your repo

Stet replays your merged PRs, scores quality above pass/fail, and delivers comparison reports through your agent.

Run it on your repo

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 15 setups: bmk_d4ba310fdf50db4ccb2092e3.

See all 15 setups on the leaderboardHow Stet measures