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Haiku 5.5 max vs Opus 5

Opus 5 leads on quality and agent time: 6.5 points higher and 2.5× faster; Haiku 5.5 max leads on cost: 1.8× cheaper.

24 tasksData from

Stet score

Haiku 5.5 maxRank 6 of 14

58.695% range 47.5–69.0

Opus 5Rank 3 of 14

65.195% range 54.8–74.96.5 points higher

A directional read: their 95% score ranges overlap.

Cost / task

Haiku 5.5 max$3.851.8× cheaper
Opus 5$6.78

Agent time / task

Haiku 5.5 max58.4 min
Opus 523.2 min2.5× faster

Task by task

Haiku 5.5 max solved 2 tasks that Opus 5 didn’t, and Opus 5 solved 4 that Haiku 5.5 max didn’t. Both solved 10; neither solved 7.

Haiku 5.5 max only 2

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

Opus 5 only 4

  • stet-232b50baPassed tests
  • stet-66762b4cPassed tests
  • stet-43493c52Passed tests
  • stet-commit-2826765eEquivalent to the merged fix

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 5Solved by
stet-3169aefaPassed testsPassed testsBoth
stet-89dfbc27Passed testsPassed testsBoth
stet-b28f4fe7Passed testsPassed testsBoth
stet-232b50baFailedPassed testsOpus 5 only
stet-5276aa3fPassed testsPassed testsBoth
stet-commit-bbbbae09Passed testsPassed testsBoth
stet-15439c21Passed testsPassed testsBoth
stet-66762b4cFailedPassed testsOpus 5 only
stet-commit-f0caded9Passed testsPassed testsBoth
stet-commit-5d766ddeEquivalent to the merged fixEquivalent to the merged fixBoth
stet-43493c52FailedPassed testsOpus 5 only
stet-6f84e978Equivalent to the merged fixPassed testsBoth
stet-commit-f8ae1177Passed testsFailedHaiku 5.5 max only
stet-2450ca2dPassed testsPassed testsBoth
stet-commit-342d0ac0Equivalent to the merged fixFailedHaiku 5.5 max only
stet-commit-5e075641FailedFailedNeither
stet-commit-2826765eFailedEquivalent to the merged fixOpus 5 only
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 maxOpus 5
Rank6 of 143 of 14
Stet score58.695% range 47.5–69.065.195% range 54.8–74.9
Solved12/249 passed, 3 judged equivalent14/2412 passed, 2 judged equivalent
Passed review9/222 not recorded9/231 not recorded
Matched merged change10/222 not recorded13/24
Cost / task$3.85$6.78
How cost was recordedreported by its harness on 23, estimated from tokens on 1reported by its harness
Agent time / task58.4 min23.2 min
Ran inDaytona sandboxsandbox not recorded

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.

Changes up to 150 lines
Haiku 5.5 maxOpus 5
Matched merged change7/101 not recorded10/11
Passed review7/101 not recorded9/101 not recorded
Cost / task$1.18$1.50
Agent time / task36.3 min18.4 min

Small fixes

7 tasks

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

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

Small fixes
Haiku 5.5 maxOpus 5
Matched merged change5/77/7
Passed review5/77/7
Cost / task$1.15$0.99
Agent time / task34.6 min15.9 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.

Larger changes
Haiku 5.5 maxOpus 5
Matched merged change3/121 not recorded3/13
Passed review2/121 not recorded0/13
Cost / task$6.11$11.24
Agent time / task77.1 min27.2 min

From the leaderboard’s routing advice

  • Small fix: use Opus 5.

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