# Claude Opus 5.5 — Anthropic's new flagship costs 40% less than Opus 5

> Anthropic's new top model matches Fable 5.1 on most work while costing 40% less per token than Opus 5.

- Org: Anthropic
- Date: 2026-09-22
- Category: model
- Source: https://www.anthropic.com/news/claude-opus-5-5
- Canonical page: https://ai-tldr.dev/releases/anthropic-claude-opus-5-5/

## In short

Claude Opus 5.5 is Anthropic's new flagship model, priced at $4 per million input tokens and $20 per million output tokens — 40% less to run than Opus 5. It scores 66.4% on Terminal-Bench 4.0 with a 1M-token context window.

## What it is

Claude Opus 5.5 opens the Claude 5.5 family and takes the top slot for long-running agentic coding and knowledge work. Anthropic prices it at $4 per million input tokens and $20 per million output tokens, against $10 / $50 for Claude Fable 5.1. The model carries a 1M-token context window, a 128K-token output limit, and a June 2026 knowledge cutoff.

## How it works

Adaptive thinking is always on and cannot be switched off — depth is steered by an `effort` parameter that defaults to `medium` rather than a manual token budget. That change comes with four breaking differences from Opus 5: thinking cannot be disabled, forced tool use returns an error, thinking blocks are pinned to the model and conversation that produced them, and the older `computer_20251124` computer-use tool is rejected on the Claude API and Google Cloud. Text between tool calls now arrives inside `thinking` blocks that are empty at the default `display` setting.

## Why it matters

Frontier-level results at $4 / $20 change the arithmetic for teams running agents for hours at a time, where token spend — not capability — is usually the limit. Anthropic reports output generated more than 30% faster and fewer tokens used per task, and says one early tester finished a 680,000-line code migration in under a day. Anthropic also reports its highest alignment audit scores for the model, describing it as less likely than recent models to take hard-to-reverse actions and more resistant to prompt injection.

## Who it's for

teams building coding agents and long-running automation

## Try it

Model ID `claude-opus-5-5` on the Claude API, Amazon Bedrock, Google Cloud and Microsoft Foundry

## Quick facts

- Maker: Anthropic
- Model ID: claude-opus-5-5
- Context window: 1M tokens
- Max output: 128K tokens
- Knowledge cutoff: Jun 2026
- Thinking: Adaptive, always on
- Availability: Claude API, Amazon Bedrock, Google Cloud, Microsoft Foundry

## FAQ

### How much does Claude Opus 5.5 cost?

Claude Opus 5.5 costs $4 per million input tokens and $20 per million output tokens on the Claude API. Cache reads are $0.20 per million and a 5-minute cache write is $5 per million. Batch API requests take 50% off both sides. That is 40% less to run than Claude Opus 5, and well under Claude Fable 5.1 at $10 / $50.

### What breaks when upgrading from Claude Opus 5 to Claude Opus 5.5?

Four changes break existing Claude Opus 5 code. Thinking can no longer be disabled, forced tool use returns an error, thinking blocks are tied to the model and conversation that produced them, and the `computer_20251124` computer-use tool is rejected on the Claude API and Google Cloud. Anthropic publishes a migration guide covering each one.

### How does Claude Opus 5.5 compare to Claude Opus 5?

Claude Opus 5.5 beats Claude Opus 5 across Anthropic's published evaluations: 66.4% versus 52.3% on Terminal-Bench 4.0, 54.4% versus 48.0% on FrontierCode v1.1, and 67.7% versus 63.6% on Humanity's Last Exam. Anthropic also reports output generated over 30% faster and fewer tokens spent per task, at 40% lower cost.

### Where can I run Claude Opus 5.5?

Claude Opus 5.5 runs on the Claude API, Amazon Bedrock, Google Cloud and Microsoft Foundry, plus Claude Platform on AWS. The model ID is `claude-opus-5-5` everywhere except Amazon Bedrock, which uses `anthropic.claude-opus-5-5`. It also powers claude.ai and the Claude apps, including Claude Code.

## Links

- [Announcement](https://www.anthropic.com/news/claude-opus-5-5)
- [Model Docs](https://platform.claude.com/docs/en/models/opus-5-5/overview)
- [What's New](https://platform.claude.com/docs/en/models/opus-5-5/whats-new-opus-5-5)
- [System Card](https://www.anthropic.com/claude-opus-5-5-system-card)
- [HN Discussion](https://news.ycombinator.com/item?id=49803892)