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GPT 5.6 Luna low vs GPT 6 Luna max

GPT 5.6 Luna low leads on speed and cost; quality is too close to call.

Quality
+1.5 pts
GPT 6 Luna max
1–0 head to head, 23 tied
Speed
8.9× faster
GPT 5.6 Luna low
6.7 min vs 59.7 min per task
Cost
7.3× cheaper
GPT 5.6 Luna low
$0.05 vs $0.37 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 Luna maxmax reasoningRank 13 of 17

46.595% range 41.1–51.71.5 points higher

A directional read: their 95% score ranges overlap.

Quality

Head-to-head matchups

GPT 5.6 Luna low won0

Tied23

GPT 6 Luna max won1

GPT 6 Luna max’s win share 51%, 95% range 47–56%Ties are within judge noise.

Task by task

GPT 5.6 Luna low solved 1 task that GPT 6 Luna max didn’t, and GPT 6 Luna max solved 2 that GPT 5.6 Luna low didn’t. Both solved 9; neither solved 12.

stet-commit-bbbbae09Solved by 15 of 17 setups

  • GPT 5.6 Luna lowFailed
  • GPT 6 Luna maxPassed 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 Luna maxSolved 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 Luna max only
stet-66762b4cEquivalent to the merged fixEquivalent to the merged fixBoth
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-f8ae1177FailedFailedNeither
stet-15439c21Equivalent to the merged fixFailedGPT 5.6 Luna low only
stet-2450ca2dFailedFailedNeither
stet-commit-342d0ac0FailedEquivalent to the merged fixGPT 6 Luna max 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 Luna max
Harnesscodex—
Reasoning effortlowmax
Rank15 of 1713 of 17
Stet score45.095% range 39.1–50.446.595% range 41.1–51.7
Solved10/246 passed, 4 judged equivalent11/247 passed, 4 judged equivalent
Cost / task$0.05$0.37
Agent time / task6.7 min59.7 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