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Haiku 5.5 low vs Opus 4.8

Haiku 5.5 low leads on quality, cost and agent time: 1.1 points higher, 28.1× cheaper and 2.4× faster.

24 tasksData from

Stet score

Haiku 5.5 lowRank 10 of 14

41.395% range 34.8–47.81.1 points higher

Opus 4.8Rank 11 of 14

40.295% range 30.3–50.3

A directional read: their 95% score ranges overlap.

Cost / task

Haiku 5.5 low$0.2528.1× cheaper
Opus 4.8$7.05

Agent time / task

Haiku 5.5 low9.9 min2.4× faster
Opus 4.823.3 min

Task by task

Haiku 5.5 low solved 0 tasks that Opus 4.8 didn’t, and Opus 4.8 solved 2 that Haiku 5.5 low didn’t. Both solved 11; neither solved 11.

Haiku 5.5 low only 0

Opus 4.8 only 2

  • 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
TaskHaiku 5.5 lowOpus 4.8Solved 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-15439c21Equivalent to the merged fixPassed testsBoth
stet-66762b4cEquivalent to the merged fixPassed testsBoth
stet-commit-f0caded9Equivalent to the merged fixEquivalent to the merged fixBoth
stet-commit-5d766ddeEquivalent to the merged fixEquivalent to the merged fixBoth
stet-43493c52Passed testsPassed testsBoth
stet-6f84e978FailedPassed testsOpus 4.8 only
stet-commit-f8ae1177FailedFailedNeither
stet-2450ca2dFailedFailedNeither
stet-commit-342d0ac0FailedFailedNeither
stet-commit-60a0e6c2FailedPassed testsOpus 4.8 only
stet-commit-5e075641FailedFailedNeither
stet-commit-2826765eFailedFailedNeither
stet-commit-a8716b88FailedFailedNeither
stet-commit-30506f8eFailedFailedNeither
stet-commit-87814583FailedFailedNeither
stet-commit-d2ab0c25FailedFailedNeither
stet-commit-e41c2e2dFailedFailedNeither
stet-commit-e928166fFailedFailedNeither

Side by side

Side by side
MetricHaiku 5.5 lowOpus 4.8
Rank10 of 1411 of 14
Stet score41.395% range 34.8–47.840.295% range 30.3–50.3
Solved11/247 passed, 4 judged equivalent13/2411 passed, 2 judged equivalent
Passed review8/248/231 not recorded
Matched merged change9/2411/24
Cost / task$0.25$7.05
How cost was recordedreported by its harnessreported by its harness
Agent time / task9.9 min23.3 min
Ran inDaytona sandboxlocal Docker

Where each setup is the better choice

The leaderboard’s readings on groups of tasks. Each group holds fewer tasks than the overall standings, so treat these as leads to test on your repo.

Changes up to 150 lines

11 tasks

11 tasks whose merged change was 2–149 lines in 1–2 files. The 7 small fixes below are among them.

Opus 4.8 matched the merged change more often: 9 of 11 to Haiku 5.5 low’s 7.

Changes up to 150 lines
Haiku 5.5 lowOpus 4.8
Matched merged change7/119/11
Passed review7/118/11
Cost / task$0.02$1.41
Agent time / task2.8 min12.8 min

Small fixes

7 tasks

7 tasks whose instructions start with “Fix”. Their merged changes were 4–29 lines in 1–2 files.

Opus 4.8 matched the merged change more often: 7 of 7 to Haiku 5.5 low’s 5.

Small fixes
Haiku 5.5 lowOpus 4.8
Matched merged change5/77/7
Passed review5/77/7
Cost / task$0.01$1.17
Agent time / task2.7 min9.7 min

Larger changes

13 tasks

13 tasks whose merged change ran over 150 lines or more than 3 files: 113–1,420 lines in 2–19 files.

Both matched the merged change on 2 of 13.

Larger changes
Haiku 5.5 lowOpus 4.8
Matched merged change2/132/13
Passed review1/130/121 not recorded
Cost / task$0.45$11.83
Agent time / task15.9 min32.2 min

From the leaderboard’s routing advice

  • Subagents: use Haiku 5.5 low.

See which setup wins on your repo

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Run it on your repo