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DeepSeek V4.1 Flash max vs Haiku 5.5 low

No clear quality winner: DeepSeek V4.1 Flash max won 8, Haiku 5.5 low won 6, 10 tied; Haiku 5.5 low leads on cost and agent time: 2.0× cheaper and 5.0× faster.

24 tasksData from

Stet score

DeepSeek V4.1 Flash maxdeepseek-harness · max reasoningRank 11 of 16

45.995% range 35.5–56.17.0 points higher

Haiku 5.5 lowclaude-code · low reasoningRank 13 of 16

38.995% range 32.6–45.4

A directional read: their 95% score ranges overlap.

Cost / task

DeepSeek V4.1 Flash max$0.49from 23/24 tasks
Haiku 5.5 low$0.252.0× cheaper

Agent time / task

DeepSeek V4.1 Flash max49.3 min
Haiku 5.5 low9.9 min5.0× faster

Quality

Head-to-head matchups

DeepSeek V4.1 Flash max won8

Tied10

Haiku 5.5 low won6

DeepSeek V4.1 Flash max’s win share 56%, 95% range 41–72%Ties are within judge noise.

Task by task

DeepSeek V4.1 Flash max solved 1 task that Haiku 5.5 low didn’t, and Haiku 5.5 low solved 0 that DeepSeek V4.1 Flash max didn’t. Both solved 11; neither solved 12.

DeepSeek V4.1 Flash max only 1

  • 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
TaskDeepSeek V4.1 Flash maxHaiku 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-66762b4cPassed testsEquivalent to the merged fixBoth
stet-15439c21Passed testsEquivalent to the merged fixBoth
stet-commit-5d766ddePassed testsEquivalent to the merged fixBoth
stet-43493c52Passed testsPassed testsBoth
stet-commit-f0caded9Passed testsEquivalent to the merged fixBoth
stet-6f84e978FailedFailedNeither
stet-2450ca2dFailedFailedNeither
stet-commit-342d0ac0Equivalent to the merged fixFailedDeepSeek V4.1 Flash max only
stet-commit-f8ae1177FailedFailedNeither
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 maxHaiku 5.5 low
Harnessdeepseek-harnessclaude-code
Reasoning effortmaxlow
Rank11 of 1613 of 16
Stet score45.995% range 35.5–56.138.995% range 32.6–45.4
Solved12/2411 passed, 1 judged equivalent11/247 passed, 4 judged equivalent
Cost / task$0.49from 23/24 tasks$0.25
Agent time / task49.3 min9.9 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 16 setups: bmk_d4ba310fdf50db4ccb2092e3.

See all 16 setups on the leaderboardHow Stet measures