Anthropic · Claude Sonnet · Available

Claude Sonnet 5.5

Claude Sonnet 5.5 (claude-sonnet-5-5) is an Anthropic model launched on September 28, 2026 on the Claude API, Claude in Amazon Bedrock, Claude Platform on AWS, Claude on Google Cloud and Claude in Microsoft Foundry. It costs $2 per 1M input tokens and $10 per 1M output tokens, with $0.20 per 1M cache reads, and has a 1M-token context window and 128K max output. In Claude Code it is the default Sonnet model on the Anthropic API.

Updated 2026-09-30· today

Claude on aistack.sh

API price per 1M tokens

$2 in / $10 out

Context window

1M tokens

Claude Sonnet 5.5 specs

Released	Sep 28, 2026
Status	Available
API model ID	`claude-sonnet-5-5`
API price (in / out)	$2 / $10 per 1M tokens
Cache read	$0.20 per 1M tokens
Context window	1M tokens
Platforms	Claude API, Claude in Amazon Bedrock, Claude Platform on AWS, Claude on Google Cloud, Claude in Microsoft Foundry

Where you can use Claude Sonnet 5.5

Claude Code

Claude Code 2.1.284 added Sonnet 5.5 as the default Sonnet model on the Anthropic API.

Claude Code

In Claude Code, Sonnet 5.5 defaults to medium effort.

Claude Code

In Claude Code, thinking cannot be turned off on Sonnet 5.5; the model decides per step how much to think based on the effort level.

Claude

The Claude Help Center has an article on why Claude switched models in a conversation with Sonnet 5.5.

Anthropic says code written for Claude Sonnet 5 can break on Claude Sonnet 5.5 in five ways.
US-only inference through the inference_geo parameter adds a 1.1x multiplier to all token prices for Claude 4.6 and later models.

Claude Sonnet 5.5 FAQ

How much does Claude Sonnet 5.5 cost on the API?

$2 per 1M input tokens and $10 per 1M output tokens. Cache reads cost $0.20 per 1M tokens, and cache writes cost $2.50 (5-minute) or $4 (1-hour) per 1M tokens.

What is the Claude Sonnet 5.5 context window?

1M tokens, with up to 128K output tokens, according to Anthropic's models overview.

Where is Claude Sonnet 5.5 available?

On the Claude API, Claude in Amazon Bedrock, Claude Platform on AWS, Claude on Google Cloud and Claude in Microsoft Foundry, per the September 28, 2026 release notes.