GLM 5.3 Flash high vs GPT 6 Luna max

No clear quality winner: GPT 6 Luna max won 17, GLM 5.3 Flash high won 4, 3 tied; GPT 6 Luna max leads on cost: 1.1× cheaper; GLM 5.3 Flash high leads on agent time: 2.2× faster.

24 tasksData from October 29, 2026

Stet score

GLM 5.3 Flash highcodex · high reasoningRank 15 of 16

29.095% range 19.9–39.3

GPT 6 Luna maxcodex · max reasoningRank 10 of 16

47.495% range 38.0–56.418.4 points higher

Other setups

Muse Wonder Full low

70.4

GPT 5.6 Luna max

70.3

SWE-2 Max high

64.3

GPT 6.1 Sol medium

62.5

Opus 5 medium

62.3

Grok 4.7 high

60.7

Pareto 26.9 medium

57.1

Haiku 5.5 max

55.5

GPT 6 Sol medium

55.4

DeepSeek V4.1 Flash max

45.9

Opus 4.8 medium

39.2

Haiku 5.5 low

38.9

Muse Spark 1.3 high

31.9

GPT 6 Luna low

19.9

A directional read: their 95% score ranges overlap.

Cost / task

GLM 5.3 Flash high$0.41

GPT 6 Luna max$0.371.1× cheaper

Agent time / task

GLM 5.3 Flash high26.7 min2.2× faster

GPT 6 Luna max59.7 min

Quality

Head-to-head matchups

GLM 5.3 Flash high won4

Tied3

GPT 6 Luna max won17

GPT 6 Luna max’s win share 75%, 95% range 59–90%Ties are within judge noise.

Task by task

GLM 5.3 Flash high solved 1 task that GPT 6 Luna max didn’t, and GPT 6 Luna max solved 4 that GLM 5.3 Flash high didn’t. Both solved 8; neither solved 11.

GLM 5.3 Flash high only 1

stet-15439c21Passed tests

GPT 6 Luna max only 4

stet-commit-5d766ddeEquivalent to the merged fix
stet-43493c52Passed tests
stet-commit-342d0ac0Equivalent to the merged fix
stet-commit-f8ae1177Passed 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
Task	GLM 5.3 Flash high	GPT 6 Luna max	Solved by
`stet-3169aefa`	Passed tests	Passed tests	Both
`stet-89dfbc27`	Passed tests	Passed tests	Both
`stet-b28f4fe7`	Passed tests	Passed tests	Both
`stet-232b50ba`	Passed tests	Passed tests	Both
`stet-5276aa3f`	Passed tests	Passed tests	Both
`stet-commit-bbbbae09`	Passed tests	Passed tests	Both
`stet-66762b4c`	Passed tests	Equivalent to the merged fix	Both
`stet-15439c21`	Passed tests	Failed	GLM 5.3 Flash high only
`stet-commit-5d766dde`	Failed	Equivalent to the merged fix	GPT 6 Luna max only
`stet-43493c52`	Failed	Passed tests	GPT 6 Luna max only
`stet-commit-f0caded9`	Passed tests	Equivalent to the merged fix	Both
`stet-6f84e978`	Failed	Failed	Neither
`stet-2450ca2d`	Failed	Failed	Neither
`stet-commit-342d0ac0`	Failed	Equivalent to the merged fix	GPT 6 Luna max only
`stet-commit-f8ae1177`	Failed	Passed tests	GPT 6 Luna max only
`stet-commit-60a0e6c2`	Failed	Failed	Neither
`stet-commit-5e075641`	Failed	Failed	Neither
`stet-commit-2826765e`	Failed	Failed	Neither
`stet-commit-a8716b88`	Failed	Failed	Neither
`stet-commit-e928166f`	Failed	Failed	Neither
`stet-commit-30506f8e`	Failed	Failed	Neither
`stet-commit-87814583`	Failed	Failed	Neither
`stet-commit-d2ab0c25`	Failed	Failed	Neither
`stet-commit-e41c2e2d`	Failed	Failed	Neither

Side by side

Side by side
Metric	GLM 5.3 Flash high	GPT 6 Luna max
Harness	codex	codex
Reasoning effort	high	max
Rank	15 of 16	10 of 16
Stet score	29.095% range 19.9–39.3	47.495% range 38.0–56.4
Solved	9/249 passed, 0 judged equivalent	12/248 passed, 4 judged equivalent
Cost / task	$0.41	$0.37
Agent time / task	26.7 min	59.7 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 October 29, 2026.
Both setups come from the same leaderboard run of 16 setups: bmk_d4ba310fdf50db4ccb2092e3.

See all 16 setups on the leaderboard How Stet measures