Available on Julius

Anthropic: Claude Opus 5.5

Work through sustained research and analysis, with room to inspect the evidence and revise the answer.

Try Claude Opus 5.5 on Julius

Explore a worked example

Available on Pro, Max, Ultra, and Business. Compare plans

Reviewed October 13, 2026 · Sources

Research report showing conversion falling for both visitor segments despite a higher overall rate caused by a changing visitor mix. — Conversion analysis reportIllustrative output · Fictional dataView full size

Best suited to: Sustained research, coding, and knowledge work
Published context: 1,000,000 tokens
Native inputs: Text and images
Released: September 22, 2026

Claude Opus 5.5 pricing

Compare the provider’s API rates with access through Julius.

Anthropic API

Input / 1M tokens: $4
Output / 1M tokens: $20

Standard API rates per million tokens. Caching, batch processing, and optional tools have separate rates.

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Available on Pro, Max, Ultra, and Business. Credits cover the work performed with models and tools.

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Prices in USD, reviewed October 13, 2026. API token charges are separate from Julius subscriptions and credits.

What is Claude Opus 5.5?

Claude Opus 5.5 is Anthropic’s model for extended coding and knowledge work. It combines a one-million-token context window with adaptive reasoning and text and image understanding.

Try Opus for a project that needs continuity across several steps, such as reading source files, developing an analysis, and explaining the result. Define the deliverable and ask it to identify missing evidence before drafting.

Work through longer tasks

Anthropic recommends Opus 5.5 as a starting point for most workloads, including extended coding and knowledge work.

Reasoning throughout a task

Adaptive thinking is always on in the provider API. Julius exposes the supported thinking levels in its model menu.

Find the mix shift behind a conversion increase

Overall conversion improved, yet both visitor segments performed worse. Can both be true?

Worked example · Fictional sample data · Expected results calculated from the CSVs

1. Input
Visitors and conversions
2. Check
Hold the visitor mix constant
3. Deliver
A fair conversion comparison

Expected result

Overall conversion rises from 6.4% to 16.7%. New-visitor conversion falls from 5% to 4%, and returning-visitor conversion falls from 20% to 18%. With the original visitor mix, week 2 is only 5.3%.

Week 2, observed mix: 16.7%
Week 2, original mix: 5.3%

Overall conversion · percent of visitors

Week 1: 6.4%
Week 2: 16.7%
Week 2, fixed mix: 5.3%

What the analysis needs to catch

The aggregate increase comes from a larger share of returning visitors. It does not show that either segment improved.

Make this deliverable

A segment comparison and a memo separating mix from performance.

Present the segment comparison and explain the mix shift with the AI presentation maker.

Try this example in Julius

The prompt includes the sample data. Review it in chat before sending. Results may vary; compare your answer with the calculations shown here.

View the sample output (PNG)View the workflow and chart (SVG)Download conversions.csv Download all data and calculations

View the prompt and sample data

Calculate conversion by week and by visitor segment. Explain whether the overall improvement reflects better within-segment conversion or a change in visitor mix. Recalculate week 2 using week 1 segment weights. Build a comparison chart and a concise review memo. Treat this as observational data, not evidence of causation.

conversions.csv

week,segment,visitors,purchases
1,New,1000,50
1,Returning,100,20
2,New,100,4
2,Returning,1000,180

These expected results come from the downloadable Python calculations. This example illustrates a workflow; it is not a measured benchmark of Claude Opus 5.5.

Using Claude Opus 5.5 in Julius

Start with your task

The try buttons carry Claude Opus 5.5 into a new chat when your plan includes it. Example buttons also fill the composer with the sample data. Review the prompt, or replace it with your own files and question, before sending.

If the model is unavailable on your plan, Julius explains the access requirement. You can choose another option in the model menu.

Research a question Work through an analysis in code Create a report

Know the boundaries

More reasoning can increase time and credit usage. Use a focused question and a clear stopping point.
Provider benchmark results depend on tools, prompts, and effort settings. They are not measured performance guarantees for your Julius workflow.

Model details and official research

Go to the original documentation for specifications, release details, and evaluation methods.

Claude Opus 5.5 documentation

Official specifications, capabilities, pricing, and links to the announcement.

Claude Opus 5.5: frequently asked questions

Is Claude Opus 5.5 available on Julius?

Yes. It appears as Claude Opus 5.5 in the model menu. Available on Pro, Max, Ultra, and Business plans.

How much does Claude Opus 5.5 cost?

Anthropic lists $4 per million input tokens and $20 per million output tokens. Standard API rates per million tokens. Caching, batch processing, and optional tools have separate rates. Julius subscriptions and credits are separate.

When should I choose Opus instead of Fable?

Anthropic recommends starting with Opus 5.5 for most workloads and considering Fable 5.1 when demanding reasoning tasks still fall short. Try the same task with clear success criteria before moving to the more expensive API model.