# 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.

URL: https://aistack.sh/model/claude-sonnet-5-5
Vendor: Anthropic (product page: https://aistack.sh/tool/claude)
Last checked against sources: 2026-09-30

## 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 it

- Claude Code (https://aistack.sh/tool/claude-code): Claude Code 2.1.284 added Sonnet 5.5 as the default Sonnet model on the Anthropic API.
- Claude Code (https://aistack.sh/tool/claude-code): In Claude Code, Sonnet 5.5 defaults to medium effort.
- Claude Code (https://aistack.sh/tool/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 (https://aistack.sh/tool/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.

## 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.

### Is Claude Sonnet 5.5 the default in Claude Code?

Claude Code 2.1.284 made it the default Sonnet model on the Anthropic API. It runs at medium effort by default, and thinking cannot be turned off.

## Sources

- [Anthropic: Claude Code changelog](https://code.claude.com/docs/en/changelog), read 2026-09-30
- [Anthropic: Claude Platform release notes](https://docs.claude.com/en/release-notes/overview), read 2026-09-30
- [Anthropic: Pricing](https://platform.claude.com/docs/en/about-claude/pricing), read 2026-09-30
- [Anthropic: Models overview](https://platform.claude.com/docs/en/about-claude/models/overview), read 2026-09-30
- [Anthropic: Model configuration](https://code.claude.com/docs/en/model-config), read 2026-09-30
- [Anthropic: Use Claude Code with your Pro or Max plan](https://support.claude.com/en/articles/11145838-using-claude-code-with-your-pro-or-max-plan), read 2026-09-30