Claude Opus 5.5 Is Now Available in EidoStack

Claude Opus 5.5 is now available in EidoStack.

Anthropic recently released the latest version of its Opus model, and I have added it to the EidoStack model catalog.

If you already use Anthropic in EidoStack, you can select Claude Opus 5.5 and start testing it with your existing API key.

What is new in Claude Opus 5.5?

Claude Opus 5.5 is Anthropic's latest Opus model, designed for complex reasoning, coding, agentic workflows, and knowledge work.

The model provides:

• 1 million token context window
• up to 128,000 output tokens
• text and image input
• adaptive thinking
• configurable reasoning effort
• $4 per million input tokens
• $20 per million output tokens

These specifications match Anthropic's official Claude Opus 5.5 documentation. Adaptive thinking is always enabled, while the effort parameter controls how deeply the model reasons about a task.

Test Claude Opus 5.5 with your own prompts

Model specifications are useful, but they do not tell you how a model will perform on your application.

The more interesting question is how Claude Opus 5.5 behaves with the prompts and workloads you actually use.

In EidoStack, you can run your own prompts against Claude Opus 5.5 and inspect:

• model responses;
• input and output token usage;
• estimated API cost;
• context-window usage;
• conversation behavior;
• system-prompt behavior.

This makes it easier to evaluate the model under conditions that are closer to your real application.

Compare Claude Opus 5.5 with other models

Claude Opus 5.5 is also available in Compare mode.

You can send the same prompt to two models and inspect their responses side by side.

For example:

• Claude Opus 5.5 vs Claude Opus 5
• Claude Opus 5.5 vs Claude Sonnet
• Claude Opus 5.5 vs GPT
• Claude Opus 5.5 vs Gemini

This is particularly useful when a new model is released.

Instead of evaluating it separately and trying to remember how another model responded, you can keep the task consistent and compare the results directly.

You can then look at both response quality and operational characteristics such as token usage and estimated cost.

Is the new model worth using?

That is the question I find most interesting whenever a new model appears.

A newer model is not automatically the right model for every application.

Claude Opus 5.5 may produce a better result for a difficult coding or reasoning task, while another model may provide sufficient quality at a lower cost for a simpler workload.

The answer depends on the task.

That is why I prefer testing new models against real prompts instead of relying only on benchmarks or model announcements.

With Claude Opus 5.5 now available in EidoStack, you can run that comparison yourself.

Claude Opus 5.5 is available in EidoStack now.