Claude Sonnet 4.5: release date and what it's for

Released September 29, 2025, according to Anthropic's announcement. Costs more than Sonnet 5 and gives you less. It's here because a lot of production code still pins to it.

Status

Live

Released

Sep 29, 2025

Lab

Anthropic

Input

$3per million tokens

Output

$15per million tokens

Context window

200Ktokens

Max output

64Ktokens

API model ID: claude-sonnet-4-5-20250929

Explained: Claude models explained: Opus 5.5, Fable 5.1, Mythos and why there's no Opus 5.1

What is Claude Sonnet 4.5 capable of?

3 posts from people showing what they made with Claude Sonnet 4.5, newest and most-reacted first.

Each card is the original post, shown the way X or Reddit embeds it, with a link to where it came from. We picked the ones that show something being made and skipped the benchmark screenshots. We can't vouch for any of them being unedited.

Demos from every model

What we've written about Claude Sonnet 4.5

How Claude Sonnet 4.5 compares on price and context

Next to the newest Anthropic models and the current model from other labs. Prices are in US dollars per million tokens.

What is Claude Sonnet 4.5?

Claude Sonnet 4.5 is a model from Anthropic, built in the US. It's out, and you can use it today.

When did Claude Sonnet 4.5 come out?

Anthropic released it on September 29, 2025. That date comes from Anthropic's announcement.

More from Anthropic

More news: Anthropic news and Claude updates

Updated 2026-10-20 20:32 UTC.