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GLM 5.3 Flash high vs Opus 5 medium

No clear quality winner: Opus 5 medium won 18, GLM 5.3 Flash high won 3, 3 tied; GLM 5.3 Flash high leads on cost: 16.5× cheaper; Opus 5 medium leads on agent time: 1.2× faster.

24 tasksData from

Stet score

GLM 5.3 Flash highcodex · high reasoningRank 14 of 15

29.995% range 20.6–40.1

Opus 5 mediummedium reasoningRank 4 of 15

63.795% range 53.3–73.633.8 points higher

Their 95% score ranges don’t overlap.

Cost / task

GLM 5.3 Flash high$0.4116.5× cheaper
Opus 5 medium$6.78

Agent time / task

GLM 5.3 Flash high26.7 min
Opus 5 medium23.2 min1.2× faster

Quality

Head-to-head matchups

GLM 5.3 Flash high won3

Tied3

Opus 5 medium won18

Opus 5 medium’s win share 82%, 95% range 67–94%Ties are within judge noise.

Task by task

GLM 5.3 Flash high solved 0 tasks that Opus 5 medium didn’t, and Opus 5 medium solved 5 that GLM 5.3 Flash high didn’t. Both solved 9; neither solved 10.

GLM 5.3 Flash high only 0

Opus 5 medium only 5

  • stet-commit-5d766ddeEquivalent to the merged fix
  • stet-43493c52Passed tests
  • stet-6f84e978Passed tests
  • stet-2450ca2dPassed tests
  • stet-commit-2826765eEquivalent 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
TaskGLM 5.3 Flash highOpus 5 mediumSolved 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 testsPassed testsBoth
stet-66762b4cPassed testsPassed testsBoth
stet-commit-5d766ddeFailedEquivalent to the merged fixOpus 5 medium only
stet-commit-f0caded9Passed testsPassed testsBoth
stet-43493c52FailedPassed testsOpus 5 medium only
stet-6f84e978FailedPassed testsOpus 5 medium only
stet-2450ca2dFailedPassed testsOpus 5 medium only
stet-commit-f8ae1177FailedFailedNeither
stet-commit-342d0ac0FailedFailedNeither
stet-commit-60a0e6c2FailedFailedNeither
stet-commit-5e075641FailedFailedNeither
stet-commit-2826765eFailedEquivalent to the merged fixOpus 5 medium only
stet-commit-a8716b88FailedFailedNeither
stet-commit-e928166fFailedFailedNeither
stet-commit-30506f8eFailedFailedNeither
stet-commit-87814583FailedFailedNeither
stet-commit-d2ab0c25FailedFailedNeither
stet-commit-e41c2e2dFailedFailedNeither

Side by side

Side by side
MetricGLM 5.3 Flash highOpus 5 medium
Harnesscodex—
Reasoning efforthighmedium
Rank14 of 154 of 15
Stet score29.995% range 20.6–40.163.795% range 53.3–73.6
Solved9/249 passed, 0 judged equivalent14/2412 passed, 2 judged equivalent
Cost / task$0.41$6.78
Agent time / task26.7 min23.2 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 15 setups: bmk_d4ba310fdf50db4ccb2092e3.

See all 15 setups on the leaderboardHow Stet measures