> Claude Sonnet 4.5 is a closed AI model from Anthropic, released 29 Sep 2025. Index score 146 (GPT-4 = 100), rank 67 of 229 ranked models. API price $3.0 in / $15 out per million tokens, 1M context.

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# Claude Sonnet 4.5

Anthropic

Released 29 Sep 2025

Closed

Flagship

Date verified

[Compare](https://themodelindex.org/compare/claude-sonnet-4-5-vs-deepseek-v3-2-exp/) [Announcement](https://www.anthropic.com/news/claude-sonnet-4-5)

146135–157

Index score

#67 of 229 models

7/ 8

Core tests taken

5 of 6 areas · plus 19 anchor tests

−8

Versus the frontier at release

best then: GPT-5

Replaced by [Claude Sonnet 4.6](https://themodelindex.org/models/claude-sonnet-4-6/)

$3.0/ $15

Price per million tokens

input / output, list price

1M

Context window

tokens it reads at once

## Where it sits · on the frontier

_Chart: Model Index score of every scored model since late 2022, with the best closed and best open model over time_

o3 reached this score 5 months earlier.

## Test results · by area · tick = best by any model

Show 15 anchor tests

Reasoning & knowledge

evidence

GPQA Diamond

82%

Humanity's Last Exam

14%

Maths

evidence

FrontierMath T1-3

24%

Coding

evidence

SWE-bench Verified

71%

Terminal-Bench

47%

Agents

evidence

APEX-Agents

no result

Novel problems

evidence

ARC-AGI-2

14%

Long tasks

evidence

METR time horizon

2.0 h

Independent results from the Epoch AI benchmarking hub, best reasoning setting. The core tests are shown here; anchor tests also inform the score and can be shown above.

## What others say · rank on each leaderboard

The Model Index

independent tests, our method

#67

of 219 · 146

Epoch Capabilities Index

overall capability from many benchmarks

#64

of 239 · 146.8

Further left is better. Leaderboards measure different things: LMArena is people voting blind between two answers, the others are test scores. Click any row for the source.

## Best at · top three among current models

3rd

SWE-bench Verified

Epoch AI · independent

Where this model places in the top three of today's models, on category leaderboards and on our core tests.

## Where to use it · prices checked 1 Oct 2026

#### From the lab

Claude

app · subscription

↗

Claude API

API

↗

#### API providers · 5 · per million tokens, in / out

C

Claude Platform on AWS

$3.0 / $15

cheapest

A

Azure

$3.0 / $15

↗

A

Amazon Bedrock

$3.3 / $16.5

↗

A

Anthropic

$3.0 / $15

↗

G

Google

$3.3 / $16.5

↗

Provider prices come from OpenRouter's live listing; going direct to a provider can differ. Subscriptions are the lab's own apps.

## Facts and sources

Released

29 Sep 2025

Announcement

[anthropic.com ↗](https://www.anthropic.com/news/claude-sonnet-4-5)

Release entry

Claude Sonnet 4.5

Scored as

Claude Sonnet 4.5

Artificial Analysis index

–

Output speed

–

Hugging Face

closed weights

## Anthropic releases · around this one

Claude Sonnet 4

Closed

22 MAY 2025

index 135

Claude Opus 4.1

Closed

5 AUG 2025

index 140

Claude Sonnet 4.5

Closed

29 SEP 2025

index 146

Claude Haiku 4.5

Closed

15 OCT 2025

index 137

Claude Opus 4.5

Closed

24 NOV 2025

index 153

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Source: https://themodelindex.org/models/claude-sonnet-4-5/ · The Model Index · data as of 2026-10-01