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DeepSeek V4.1 Flash max vs GPT 5.6 Luna max

GPT 5.6 Luna max leads on speed; DeepSeek V4.1 Flash max on cost; quality is too close to call.

Quality
+0.7 pts
DeepSeek V4.1 Flash max
2–2 head to head, 20 tied
Speed
1.7× faster
GPT 5.6 Luna max
28.5 min vs 49.3 min per task
Cost
1.8× cheaper
DeepSeek V4.1 Flash max
$0.49 vs $0.90 per task

24 tasksData from

Stet score

DeepSeek V4.1 Flash maxmax reasoningRank 8 of 17

50.695% range 47.1–54.70.7 points higher

GPT 5.6 Luna maxmax reasoningRank 9 of 17

49.995% range 44.5–55.6

A directional read: their 95% score ranges overlap.

Quality

Head-to-head matchups

DeepSeek V4.1 Flash max won2

Tied20

GPT 5.6 Luna max won2

DeepSeek V4.1 Flash max’s win share 50%, 95% range 42–58%Ties are within judge noise.

Task by task

DeepSeek V4.1 Flash max solved 3 tasks that GPT 5.6 Luna max didn’t, and GPT 5.6 Luna max solved 1 that DeepSeek V4.1 Flash max didn’t. Both solved 9; neither solved 11.

stet-commit-f0caded9Solved by 12 of 17 setups

  • DeepSeek V4.1 Flash maxFailed
  • GPT 5.6 Luna maxEquivalent 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.

All 24 compared tasks
Task by task
TaskDeepSeek V4.1 Flash maxGPT 5.6 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-bbbbae09Passed testsPassed testsBoth
stet-66762b4cPassed testsEquivalent to the merged fixBoth
stet-commit-5d766ddeEquivalent to the merged fixEquivalent to the merged fixBoth
stet-commit-f0caded9FailedEquivalent to the merged fixGPT 5.6 Luna max only
stet-43493c52Passed testsPassed testsBoth
stet-commit-f8ae1177Passed testsFailedDeepSeek V4.1 Flash max only
stet-15439c21Equivalent to the merged fixFailedDeepSeek V4.1 Flash max only
stet-2450ca2dFailedFailedNeither
stet-commit-342d0ac0Equivalent to the merged fixFailedDeepSeek V4.1 Flash 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
MetricDeepSeek V4.1 Flash maxGPT 5.6 Luna max
Reasoning effortmaxmax
Rank8 of 179 of 17
Stet score50.695% range 47.1–54.749.995% range 44.5–55.6
Solved12/249 passed, 3 judged equivalent10/247 passed, 3 judged equivalent
Cost / task$0.49from 23/24 tasks$0.90
Agent time / task49.3 min28.5 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