How to Use Claude Opus 5.5 — Complete Setup Guide

For the vast majority of non-developers, the easiest way to access Claude Opus 5.5 is directly through Anthropic's official web interface at Claude.ai. However, because Opus 5.5 is Anthropic's flagship, compute-heavy model, it is not available on the Free plan.

You will need an active subscription to one of Anthropic's paid tiers: Pro, Max, Team, or Enterprise. If you're looking for workarounds, check out our guide on how to use Claude Opus 5.5 for free.

Step-by-step instructions:

1. Log into your account at Claude.ai.
2. Ensure you are subscribed to a paid plan.
3. Start a new chat by clicking the "New Chat" button.
4. At the top (or in the prompt box), click the model selector dropdown.
5. Select Claude 5.5 Opus from the list of available models.

Bonus: At launch, Anthropic officially raised the 5-hour usage limits for all paid tiers, meaning you can chat with Opus 5.5 substantially more than you could with previous iterations before hitting a rate limit. Learn more about what makes Opus 5.5 so powerful.

If you are an engineer using Anthropic's official CLI tool, switching to Opus 5.5 is incredibly straightforward. Claude Code allows you to harness Opus 5.5 directly in your terminal for advanced refactoring and project architecture tasks.

How to switch models in Claude Code:

1. Open your terminal in your project directory.
2. Run claude to start the interactive session.
3. Type the slash command /model claude-5-5-opus-20260922 and hit enter.

Unlike older models, Claude 5.5 replaces the manual thinking toggle with adaptive Effort Settings. In Claude Code, you can specify how hard the model should think by adjusting this setting (low, medium, high, x-high, or max). When using Opus 5.5 for complex debugging, we recommend setting effort to high or max. For lighter coding tasks, you might want to learn how to use Claude Fable 5.1 for coding to save on API costs.

Developers can integrate Claude Opus 5.5 directly into their applications using the Anthropic API. At $4 per million input tokens and $20 per million output tokens (a 40% reduction from Opus 5), it offers incredible value for frontier-level intelligence.

The specific model ID to use is claude-5-5-opus-20260922.

Here is a basic Python example using the official SDK:

import anthropic

client = anthropic.Anthropic(
    api_key="your-api-key-here"
)

message = client.messages.create(
    model="claude-5-5-opus-20260922",
    max_tokens=2048,
    messages=[
        {"role": "user", "content": "Explain the significance of adaptive effort settings in AI."}
    ]
)

print(message.content[0].text)

Remember that Prompt Caching is supported for Opus 5.5, with cache reads costing just $0.20 per million tokens. For a full breakdown of the costs, check out our Claude Opus 5.5 pricing guide.

For enterprise customers with strict data governance, compliance requirements, or existing vendor lock-in, Claude Opus 5.5 is available across all major cloud providers from day one.

• Amazon Bedrock: Fully integrated for AWS customers. Ideal for leveraging existing AWS credits and IAM roles.
• Google Cloud Vertex AI: Available in the Model Garden for easy deployment alongside GCP infrastructure.
• Azure: Microsoft's cloud platform also provides robust access to the Claude 5.5 family.

Accessing the model via these providers typically requires requesting model access in the respective cloud console before you can begin making API calls.

One of the most significant changes in the Claude 5.5 family is the introduction of adaptive effort settings. In previous versions, you either turned "thinking" on or off. Now, Anthropic has implemented an anti-distillation safeguard where thinking cannot be completely disabled, but it can be scaled.

You can adjust the effort level depending on the task:

Keep in mind that higher effort settings mean the model spends more time generating "thinking" tokens before returning the final output. While this produces vastly superior reasoning, it will consume your usage limits or API budget much faster. Use "Max" sparingly!

To get the absolute best performance out of Claude Opus 5.5 (which scores an impressive 66.4% on Terminal-Bench 4.0), you should format your prompts to align with how Anthropic trains its models.

• Use XML Tags for Structure: Claude is explicitly trained to parse XML tags. Use tags like <context>, <instructions>, and <example> to clearly separate different parts of your prompt.
• Single-Shot Dense Prompts: Because of the incredible intelligence and reasoning capabilities of Opus 5.5, you no longer need to break complex tasks into a dozen small steps. You can provide a massive, dense prompt with all requirements at once, set the Effort to High, and let the model figure out the implementation details.
• Avoid Forced Tool Calls: Note that Anthropic has officially retired forced tool calls in Opus 5.5. The model is smart enough to know when to invoke a tool naturally based on your instructions.

By leveraging these techniques, you'll be writing code, analyzing data, and generating content faster and more accurately than ever before.