The Known Good Updated 25 Jul 2026
claude-sonnet-4-5-20250929 vs OpenAI: GPT-5.1 ·Anthropic vs OpenAI

claude-sonnet-4-5-20250929 vs OpenAI: GPT-5.1 — head-to-head comparison

claude-sonnet-4-5-20250929 profile OpenAI: GPT-5.1 profile All comparisons
claude-sonnet-4-5-20250929 — Anthropic
Quality
#36 of 61
59based on 5 of 6 evaluations
Known Good Index
Speed
unranked
—
Output tokens per second
Price
unranked
—
Blended per 1M tokens
Cache hit price
unranked
—
per 1M tokens
Context
unranked
—
tokens
OpenAI: GPT-5.1 — OpenAI
Quality
#20 of 61
74based on 6 of 6 evaluations
Known Good Index
Speed
#118 of 316
62.1
Output tokens per second
Price
#261 of 340
$3.44
Blended per 1M tokens
In $1.25 · Out $10.00
Cache hit price
#105 of 206
$0.12
per 1M tokens (−90%)
Context
#101 of 345
400k
tokens (~600 pages)
Summary

On the Known Good Index, claude-sonnet-4-5-20250929 scores 59 and OpenAI: GPT-5.1 scores 74 — a 15-point lead for OpenAI: GPT-5.1. They share 5 published evaluations, with claude-sonnet-4-5-20250929 ahead on 1 and OpenAI: GPT-5.1 ahead on 4.

Published pricing is tracked for OpenAI: GPT-5.1 only, at $3.44 per 1M tokens blended.

claude-sonnet-4-5-20250929 is proprietary; OpenAI: GPT-5.1 is proprietary. 2 tracked hosts serve one or both.

Generated from tracked data on 26 Jul 2026 · how these comparisons are computed →

At a glance
Metricclaude-sonnet-4-5-20250929OpenAI: GPT-5.1
Known Good Index 59 based on 5 of 6 evaluations 74 based on 6 of 6 evaluations
Blended $/1M — $3.44
Output tok/s — 62
Context window — 400k
Providers 0 2
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Quality

Known Good Index and the capability indices, side by side

IndicesComponents
Index scores

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

Metricclaude-sonnet-4-5-20250929OpenAI: GPT-5.1
Known Good Index 59 74
Coding Index 61 68
Mathematics Index 89 89
Science Index 84 91
Reasoning Index 48 80
Agentic Index 61 61
Openness Index 5 5
The Known Good

Quality Breakdown

Every evaluation both models report a published score for

Evaluations both models report

Bar = claude-sonnet-4-5-20250929 · marker = OpenAI: GPT-5.1 · scores ingested from Epoch AI (CC-BY 4.0)

GPQA Diamond82 / 88
MATH / AIME78 / 89
SWE-bench Verified71 / 68
Humanity's Last Exam8 / 24
Terminal-Bench43 / 48

Right-hand figures read claude-sonnet-4-5-20250929 / OpenAI: GPT-5.1. claude-sonnet-4-5-20250929 leads on 1 of 5, OpenAI: GPT-5.1 on 4.

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.

Metricclaude-sonnet-4-5-20250929OpenAI: GPT-5.1
Text Arena 1,438 1,422
Text Arena (style controlled) 1,455 1,439
The Known Good

Price & Cost

Published API pricing by token type

Per token typeCache discount
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.

Metricclaude-sonnet-4-5-20250929OpenAI: GPT-5.1
Input $/1M — $1.25
Output $/1M — $10.00
Blended $/1M — $3.44
Cache read $/1M — $0.125
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.

Metricclaude-sonnet-4-5-20250929OpenAI: GPT-5.1
Context window — 400k
Max output tokens — 128k
The Known Good

Speed & Latency

Median throughput and time to first token across hosting providers

Output speedTime to first token
Throughput and latency

Medians across all tracked providers, derived from OpenRouter endpoint telemetry.

Metricclaude-sonnet-4-5-20250929OpenAI: GPT-5.1
Output tokens/s — 62
Time to first token — 1.2s
The Known Good

Providers

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

2 hosts
Full provider benchmarks →
Provider claude-sonnet-4-5-20250929 blendedclaude-sonnet-4-5-20250929 tok/s OpenAI: GPT-5.1 blendedOpenAI: GPT-5.1 tok/s
OpenAI · first party — — $1.72 76
Azure · first party — — $3.44 56

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 →