Skip to the comparison
STET
Join the waitlist

Haiku 5.5 max vs Opus 4.8 medium

No clear quality winner: Haiku 5.5 max won 15, Opus 4.8 medium won 4, 4 tied, 1 undecided; Haiku 5.5 max leads on cost: 1.8× cheaper; Opus 4.8 medium leads on agent time: 2.5× faster.

24 tasksData from

Stet score

Haiku 5.5 maxclaude-code · max reasoningRank 8 of 16

55.595% range 44.6–65.716.3 points higher

Opus 4.8 mediumclaude-code · medium reasoningRank 12 of 16

39.295% range 29.0–49.7

A directional read: their 95% score ranges overlap.

Cost / task

Haiku 5.5 max$3.851.8× cheaper
Opus 4.8 medium$7.05

Agent time / task

Haiku 5.5 max58.4 min
Opus 4.8 medium23.3 min2.5× faster

Quality

Head-to-head matchups

Haiku 5.5 max won15

Tied41 undecided

Opus 4.8 medium won4

Haiku 5.5 max’s win share 71%, 95% range 55–87%Ties are within judge noise.

Task by task

Haiku 5.5 max solved 3 tasks that Opus 4.8 medium didn’t, and Opus 4.8 medium solved 3 that Haiku 5.5 max didn’t. Both solved 9; neither solved 8.

Haiku 5.5 max only 3

  • stet-2450ca2dPassed tests
  • stet-commit-342d0ac0Equivalent to the merged fix
  • stet-commit-f8ae1177Passed tests

Opus 4.8 medium only 3

  • stet-232b50baPassed tests
  • stet-66762b4cPassed tests
  • stet-43493c52Passed 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. 1 of the 24 tasks is left out because one of the two has no scored result on it.

All 23 compared tasks
Task by task
TaskHaiku 5.5 maxOpus 4.8 mediumSolved by
stet-3169aefaPassed testsPassed testsBoth
stet-89dfbc27Passed testsPassed testsBoth
stet-b28f4fe7Passed testsPassed testsBoth
stet-232b50baFailedPassed testsOpus 4.8 medium only
stet-5276aa3fPassed testsPassed testsBoth
stet-commit-bbbbae09Passed testsPassed testsBoth
stet-66762b4cFailedPassed testsOpus 4.8 medium only
stet-15439c21Passed testsPassed testsBoth
stet-commit-5d766ddeEquivalent to the merged fixEquivalent to the merged fixBoth
stet-43493c52FailedPassed testsOpus 4.8 medium only
stet-commit-f0caded9Passed testsEquivalent to the merged fixBoth
stet-6f84e978Equivalent to the merged fixPassed testsBoth
stet-2450ca2dPassed testsFailedHaiku 5.5 max only
stet-commit-342d0ac0Equivalent to the merged fixFailedHaiku 5.5 max only
stet-commit-f8ae1177Passed testsFailedHaiku 5.5 max 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
MetricHaiku 5.5 maxOpus 4.8 medium
Harnessclaude-codeclaude-code
Reasoning effortmaxmedium
Rank8 of 1612 of 16
Stet score55.595% range 44.6–65.739.295% range 29.0–49.7
Solved12/249 passed, 3 judged equivalent13/2411 passed, 2 judged equivalent
Cost / task$3.85$7.05
Agent time / task58.4 min23.3 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 16 setups: bmk_d4ba310fdf50db4ccb2092e3.

See all 16 setups on the leaderboardHow Stet measures