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GPT 5.6 Luna low vs GPT 6 Sol medium

GPT 6 Sol medium leads on quality; GPT 5.6 Luna low on speed and cost.

Quality
+8.2 pts
GPT 6 Sol medium
3–0 head to head, 21 tied
Not yet conclusive across all 136 comparisons on the board.
Speed
2.3× faster
GPT 5.6 Luna low
6.7 min vs 15.4 min per task
Cost
59.1× cheaper
GPT 5.6 Luna low
$0.05 vs $3.01 per task

24 tasksData from

Stet score

GPT 5.6 Luna lowcodex · low reasoningRank 15 of 17

45.095% range 39.1–50.4

GPT 6 Sol mediummedium reasoningRank 5 of 17

53.295% range 49.0–57.98.2 points higher

A directional read: their 95% score ranges overlap.

Quality

Head-to-head matchups

GPT 5.6 Luna low won0

Tied21

GPT 6 Sol medium won3

GPT 6 Sol medium’s win share 58%, 95% range 52–65%Ties are within judge noise.

Task by task

GPT 5.6 Luna low solved 1 task that GPT 6 Sol medium didn’t, and GPT 6 Sol medium solved 3 that GPT 5.6 Luna low didn’t. Both solved 9; neither solved 11.

stet-commit-bbbbae09Solved by 15 of 17 setups

  • GPT 5.6 Luna lowFailed
  • GPT 6 Sol mediumPassed 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
TaskGPT 5.6 Luna lowGPT 6 Sol mediumSolved by
stet-232b50baPassed testsPassed testsBoth
stet-3169aefaPassed testsPassed testsBoth
stet-5276aa3fPassed testsPassed testsBoth
stet-89dfbc27Passed testsPassed testsBoth
stet-b28f4fe7Passed testsPassed testsBoth
stet-commit-bbbbae09FailedPassed testsGPT 6 Sol medium only
stet-66762b4cEquivalent to the merged fixPassed testsBoth
stet-commit-5d766ddeEquivalent to the merged fixEquivalent to the merged fixBoth
stet-commit-f0caded9Equivalent to the merged fixEquivalent to the merged fixBoth
stet-43493c52Passed testsPassed testsBoth
stet-commit-f8ae1177FailedPassed testsGPT 6 Sol medium only
stet-15439c21Equivalent to the merged fixFailedGPT 5.6 Luna low only
stet-2450ca2dFailedFailedNeither
stet-commit-342d0ac0FailedEquivalent to the merged fixGPT 6 Sol medium only
stet-6f84e978FailedFailedNeither
stet-commit-60a0e6c2FailedFailedNeither
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
MetricGPT 5.6 Luna lowGPT 6 Sol medium
Harnesscodex—
Reasoning effortlowmedium
Rank15 of 175 of 17
Stet score45.095% range 39.1–50.453.295% range 49.0–57.9
Solved10/246 passed, 4 judged equivalent12/249 passed, 3 judged equivalent
Cost / task$0.05$3.01
Agent time / task6.7 min15.4 min

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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 17 setups: bmk_d4ba310fdf50db4ccb2092e3.

See all 17 setups on the leaderboardHow Stet measures