GLM 5.3 Flash high vs Opus 4.8 medium

No clear quality winner: Opus 4.8 medium won 13, GLM 5.3 Flash high won 7, 4 tied; GLM 5.3 Flash high leads on cost: 17.2× cheaper; Opus 4.8 medium leads on agent time: 1.1× faster.

24 tasksData from October 29, 2026

Stet score

GLM 5.3 Flash highcodex · high reasoningRank 14 of 15

29.995% range 20.6–40.1

Opus 4.8 mediumclaude-code · medium reasoningRank 12 of 15

39.895% range 29.7–50.29.9 points higher

Other setups

Muse Wonder Full low

72.4

SWE-2 Max high

65.1

GPT 6.1 Sol medium

64.1

Opus 5 medium

63.7

Grok 4.7 high

62.1

Pareto 26.9 medium

58.4

Haiku 5.5 max

57.1

GPT 6 Sol medium

57.0

GPT 6 Luna max

49.2

DeepSeek V4.1 Flash max

46.9

Haiku 5.5 low

40.1

Muse Spark 1.3 high

32.8

GPT 6 Luna low

20.4

A directional read: their 95% score ranges overlap.

Cost / task

GLM 5.3 Flash high$0.4117.2× cheaper

Opus 4.8 medium$7.05

Agent time / task

GLM 5.3 Flash high26.7 min

Opus 4.8 medium23.3 min1.1× faster

Quality

Head-to-head matchups

GLM 5.3 Flash high won7

Tied4

Opus 4.8 medium won13

Opus 4.8 medium’s win share 61%, 95% range 43–78%Ties are within judge noise.

Task by task

GLM 5.3 Flash high solved 0 tasks that Opus 4.8 medium didn’t, and Opus 4.8 medium solved 4 that GLM 5.3 Flash high didn’t. Both solved 9; neither solved 11.

GLM 5.3 Flash high only 0

Opus 4.8 medium only 4

stet-commit-5d766ddeEquivalent to the merged fix
stet-43493c52Passed tests
stet-6f84e978Passed tests
stet-commit-60a0e6c2Passed 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	Opus 4.8 medium	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-15439c21`	Passed tests	Passed tests	Both
`stet-66762b4c`	Passed tests	Passed tests	Both
`stet-commit-5d766dde`	Failed	Equivalent to the merged fix	Opus 4.8 medium only
`stet-commit-f0caded9`	Passed tests	Equivalent to the merged fix	Both
`stet-43493c52`	Failed	Passed tests	Opus 4.8 medium only
`stet-6f84e978`	Failed	Passed tests	Opus 4.8 medium only
`stet-2450ca2d`	Failed	Failed	Neither
`stet-commit-f8ae1177`	Failed	Failed	Neither
`stet-commit-342d0ac0`	Failed	Failed	Neither
`stet-commit-60a0e6c2`	Failed	Passed tests	Opus 4.8 medium only
`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	Opus 4.8 medium
Harness	codex	claude-code
Reasoning effort	high	medium
Rank	14 of 15	12 of 15
Stet score	29.995% range 20.6–40.1	39.895% range 29.7–50.2
Solved	9/249 passed, 0 judged equivalent	13/2411 passed, 2 judged equivalent
Cost / task	$0.41	$7.05
Agent time / task	26.7 min	23.3 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 15 setups: bmk_d4ba310fdf50db4ccb2092e3.

See all 15 setups on the leaderboard How Stet measures