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GPT 6 Sol medium vs Haiku 5.5 low

GPT 6 Sol medium leads on quality: 16.3 points higher; Haiku 5.5 low leads on cost and agent time: 12.0× cheaper and 1.6× faster.

24 tasksData from

Stet score

GPT 6 Sol mediumRank 7 of 14

57.695% range 49.5–65.716.3 points higher

Haiku 5.5 lowRank 10 of 14

41.395% range 34.8–47.8

Their 95% score ranges don’t overlap.

Cost / task

GPT 6 Sol medium$3.01
Haiku 5.5 low$0.2512.0× cheaper

Agent time / task

GPT 6 Sol medium15.4 min
Haiku 5.5 low9.9 min1.6× faster

Task by task

GPT 6 Sol medium solved 3 tasks that Haiku 5.5 low didn’t, and Haiku 5.5 low solved 0 that GPT 6 Sol medium didn’t. Both solved 11; neither solved 10.

GPT 6 Sol medium only 3

  • stet-6f84e978Passed tests
  • stet-commit-f8ae1177Passed tests
  • stet-commit-342d0ac0Equivalent to the merged fix

Haiku 5.5 low only 0

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
TaskGPT 6 Sol mediumHaiku 5.5 lowSolved 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 testsEquivalent to the merged fixBoth
stet-66762b4cPassed testsEquivalent to the merged fixBoth
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-6f84e978Passed testsFailedGPT 6 Sol medium only
stet-commit-f8ae1177Passed testsFailedGPT 6 Sol medium only
stet-2450ca2dFailedFailedNeither
stet-commit-342d0ac0Equivalent to the merged fixFailedGPT 6 Sol medium only
stet-commit-60a0e6c2FailedFailedNeither
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
MetricGPT 6 Sol mediumHaiku 5.5 low
Rank7 of 1410 of 14
Stet score57.695% range 49.5–65.741.395% range 34.8–47.8
Solved14/2411 passed, 3 judged equivalent11/247 passed, 4 judged equivalent
Passed review8/248/24
Matched merged change10/249/24
Cost / task$3.01$0.25
How cost was recordedestimated from tokensreported by its harness
Agent time / task15.4 min9.9 min
Ran inDaytona sandboxDaytona sandbox

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.

Haiku 5.5 low matched the merged change more often: 7 of 11 to GPT 6 Sol medium’s 6.

Changes up to 150 lines
GPT 6 Sol mediumHaiku 5.5 low
Matched merged change6/117/11
Passed review6/117/11
Cost / task$0.75$0.02
Agent time / task6.6 min2.8 min

Small fixes

7 tasks

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

Both matched the merged change on 5 of 7.

Small fixes
GPT 6 Sol mediumHaiku 5.5 low
Matched merged change5/75/7
Passed review5/75/7
Cost / task$0.60$0.01
Agent time / task5.4 min2.7 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.

GPT 6 Sol medium matched the merged change more often: 4 of 13 to Haiku 5.5 low’s 2.

Larger changes
GPT 6 Sol mediumHaiku 5.5 low
Matched merged change4/132/13
Passed review2/131/13
Cost / task$4.92$0.45
Agent time / task22.9 min15.9 min

From the leaderboard’s routing advice

  • Subagents: use Haiku 5.5 low.

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