# Claude Opus 5.5

> Claude Opus 5.5 is Anthropic's model for long-running agentic coding and knowledge work, released September 22, 2026. It has a 1M-token context window and 128k max output, and costs $4 / $20 per 1M input/output tokens on the API, down from $5 / $25 for Opus 5. It is the default model in Claude Code on Pro, Max, Team, Enterprise and the API.

URL: https://aistack.sh/model/claude-opus-5-5
Vendor: Anthropic (product page: https://aistack.sh/tool/claude)
Last checked against sources: 2026-09-24

## Specs

- Released: Sep 22, 2026
- Status: Available
- API model ID: claude-opus-5-5
- API price (in / out): $4 / $20 per 1M tokens
- Cache read: $0.20 per 1M tokens
- Context window: 1M tokens
- Plans: Pro, Max, Team, Enterprise
- Platforms: Claude API, Amazon Bedrock, Claude Platform on AWS, Google Cloud, Microsoft Foundry
- Replaces: Claude Opus 5 (https://aistack.sh/model/claude-opus-5)

## Where you can use it

- Claude (https://aistack.sh/tool/claude): Opus models are included from the Pro plan up; Free gets Sonnet and Haiku only.
- Claude Code (https://aistack.sh/tool/claude-code): Default model on Pro, Max, Team, Enterprise and the Anthropic API, and on Amazon Bedrock, Claude Platform on AWS and Google Cloud. The `opus` alias resolves to it on the Anthropic API.
- In Claude Code on Microsoft Foundry the default is Sonnet 4.5, not Opus 5.5.
- Cache reads cost 0.05x the base input price, lower than the usual 0.1x multiplier.

## Comparisons

- [Claude Fable 5.1 vs Claude Opus 5.5](https://aistack.sh/compare/claude-fable-5-1-vs-claude-opus-5-5)
- [Claude Opus 5.5 vs GPT-6 Astra](https://aistack.sh/compare/claude-opus-5-5-vs-gpt-6-astra)
- [Claude Opus 5.5 vs GPT-6 Sol](https://aistack.sh/compare/claude-opus-5-5-vs-gpt-6-sol)

## FAQ

### How much does Claude Opus 5.5 cost on the API?

$4 per 1M input tokens and $20 per 1M output tokens. Cache reads are $0.20 per 1M tokens. Claude Opus 5 costs $5 / $25, so Opus 5.5 is 20% cheaper on both input and output.

### What is the Claude Opus 5.5 context window?

1M tokens by default, with up to 128k output tokens, according to Anthropic's release notes.

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

Yes. Claude Code's model configuration docs list Opus 5.5 as the default on Pro, Max, Team, Enterprise and the Anthropic API, and on Amazon Bedrock, Claude Platform on AWS and Google Cloud. Microsoft Foundry defaults to Sonnet 4.5.

### Can I use Claude Opus 5.5 on the free Claude plan?

No. Claude's pricing page lists Sonnet and Haiku on Free; Opus models start at Pro.

### What benchmarks has Anthropic published for Claude Opus 5.5?

On its launch page Anthropic reports 66.4% on Terminal-Bench 4.0, 57.8% on CursorBench 4.0, 54.4% on FrontierCode v1.1 (Main) and 1846 Elo on GDPval-AA v2.1. These are vendor-reported figures.

## Sources

- [Claude Developer Platform release notes](https://platform.claude.com/docs/en/release-notes/overview), read 2026-09-24
- [Claude API pricing](https://platform.claude.com/docs/en/about-claude/pricing), read 2026-09-24
- [Claude models overview](https://platform.claude.com/docs/en/about-claude/models/overview), read 2026-09-24
- [Claude Code model configuration](https://code.claude.com/docs/en/model-config), read 2026-09-24
- [Claude plans and pricing](https://claude.com/pricing), read 2026-09-24
- [Anthropic: Claude Opus 5.5 launch](https://www.anthropic.com/claude-opus-5-5), read 2026-09-24