The Known Good Updated 4 Sep 2026 Subscribe
OpenAI: GPT-5 Mini vs Z.ai: GLM 5.1 ·OpenAI vs Z.ai

OpenAI: GPT-5 Mini vs Z.ai: GLM 5.1 — head-to-head comparison

OpenAI: GPT-5 Mini profile Z.ai: GLM 5.1 profile All comparisons
OpenAI: GPT-5 Mini — OpenAI
Quality
#34 of 65
67based on 6 of 7 evaluations
Known Good Index
Speed
#82 of 338
78.3
Output tokens per second
Price
#190 of 442
$0.69
Blended per 1M tokens
In $0.25 · Out $2.00
Cache hit price
#67 of 324
$0.025
per 1M tokens (−90%)
Context
#185 of 476
400k
tokens (~600 pages)
Z.ai: GLM 5.1 — Z.ai
Quality
#11 of 65
90based on 3 of 7 evaluations
Known Good Index
Speed
#222 of 338
38.7
Output tokens per second
Price
#268 of 442
$1.48
Blended per 1M tokens
In $0.97 · Out $3.04
Cache hit price
#219 of 324
$0.18
per 1M tokens (−81%)
Context
#290 of 476
205k
tokens (~300 pages)
Summary

On the Known Good Index, OpenAI: GPT-5 Mini scores 67 and Z.ai: GLM 5.1 scores 90 — a 22-point lead for Z.ai: GLM 5.1. They share 3 published evaluations, with OpenAI: GPT-5 Mini ahead on 0 and Z.ai: GLM 5.1 ahead on 3.

Blended pricing is $0.69 per 1M tokens for OpenAI: GPT-5 Mini and $1.48 for Z.ai: GLM 5.1 — OpenAI: GPT-5 Mini is about 2.2× cheaper.

Throughput is 78 tokens per second for OpenAI: GPT-5 Mini and 39 for Z.ai: GLM 5.1, with time to first token at 4.2s and 2.0s. OpenAI: GPT-5 Mini accepts 400k tokens of context against 205k.

OpenAI: GPT-5 Mini is proprietary; Z.ai: GLM 5.1 is open weights under Open weights (unrestricted). 22 tracked hosts serve one or both.

Generated from tracked data on 4 Sep 2026 · how these comparisons are computed →

At a glance
MetricOpenAI: GPT-5 MiniZ.ai: GLM 5.1
Known Good Index 67 based on 6 of 7 evaluations 90 based on 3 of 7 evaluations
Blended $/1M $0.69 $1.48
Output tok/s 78 39
Context window 400k 205k
Providers 2 20
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Quality

Known Good Index and the capability indices, side by side

Index scores

Each index is min-max normalised across tracked models and scaled 0–100 from published evaluations. We do not run these evaluations.

MetricOpenAI: GPT-5 MiniZ.ai: GLM 5.1
Known Good Index 67 90
Coding Index 51
Mathematics Index 93
Reasoning Index 57
Openness Index 5 60
The Known Good

Quality Breakdown

Every evaluation both models report a published score for

Evaluations both models report

Bar = OpenAI: GPT-5 Mini · marker = Z.ai: GLM 5.1 · scores ingested from Epoch AI (CC-BY 4.0)

GPQA Diamond75 / 90
Mock AIME 2024–2587 / 93
SWE-bench Verified65 / 74

Right-hand figures read OpenAI: GPT-5 Mini / Z.ai: GLM 5.1. OpenAI: GPT-5 Mini leads on 0 of 3, Z.ai: GLM 5.1 on 3.

The Known Good

Arena Elo

Human preference rating from blind pairwise votes

Arena ratings

Elo from blind pairwise votes, ingested from Arena. Higher is better.

MetricOpenAI: GPT-5 MiniZ.ai: GLM 5.1
Text Arena 1,463
Text Arena (style controlled) 1,466
The Known Good

Price & Cost

Published API pricing by token type

Published pricing

USD per 1M tokens. Blended is a 3:1 input:output mix. Live from OpenRouter, cross-checked against models.dev. Lower is better.

MetricOpenAI: GPT-5 MiniZ.ai: GLM 5.1
Input $/1M $0.25 $0.97
Output $/1M $2.00 $3.04
Blended $/1M $0.69 $1.48
Cache read $/1M $0.025 $0.179
The Known Good
We publish blended price rather than cost-per-task. Cost-per-task requires token counts from an evaluation suite we do not run. Blended price is computed from published rates and is fully reproducible — see the pricing methodology.

Context Window

Maximum input accepted and maximum output emitted

Context and output limits

Provider-declared limits, from metadata via models.dev and OpenRouter. Higher is better.

MetricOpenAI: GPT-5 MiniZ.ai: GLM 5.1
Context window 400k 205k
Max output tokens 128k 128k
The Known Good

Speed & Latency

Mean throughput and time to first token across hosting providers, over successful measurements from the last 48 hours

Throughput and latency

Means across all tracked providers over successful measurements from the last 48 hours, derived from OpenRouter endpoint telemetry.

MetricOpenAI: GPT-5 MiniZ.ai: GLM 5.1
Output tokens/s 78 39
Time to first token 4.2s 2.0s
The Known Good

Providers

Which hosts serve each model, and at what price and speed

22 hosts
Full provider benchmarks →
Provider OpenAI: GPT-5 Mini blendedOpenAI: GPT-5 Mini tok/s Z.ai: GLM 5.1 blendedZ.ai: GLM 5.1 tok/s
Azure · first party $0.69 116
OpenAI · first party $0.34 75
Crusoe $2.00 92
CoreWeave $2.15 79
Friendli $2.15 69
Wafer $1.55 60
Baidu · first party $2.15 58
GMICloud $1.40 56
Alibaba · first party $2.04 55
AtlasCloud $1.94 47
Chutes $1.50 38
Novita $2.13 36
Venice $2.37 34
Phala $1.96 32
DeepInfra $1.66 31
StreamLake $1.48 31
Nebius $2.15 27
SiliconFlow $1.83 27
Z.AI · first party $2.15 17
DigitalOcean $2.05 12
Fireworks $2.15
Parasail $2.15

Per-host pricing and telemetry from OpenRouter. A dash means that host does not serve that model.

The Known Good
Sources for this page
Pricing & providers — OpenRouter Metadata — models.dev Benchmarks — Epoch AI (CC-BY 4.0)Elo — Arena Full attribution →