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Claude Sonnet 5.5 in the EU, processed in European data centres

Claude Sonnet 5.5 is Anthropic's mid-sized frontier model, released in September 2026, built for everyday coding, agent and business work with a one-million-token context window. On inference.eu you call it with the Anthropic Messages or OpenAI request format, processed in EU data centres and never used for training.

Contact salesExample request
  1. 01Context window: 1,000,000 tokens
  2. 02EU data centres
  3. 03Proprietary

What Claude Sonnet 5.5 is

Claude Sonnet 5.5 is a closed model from Anthropic, released on 28 September 2026 as the second model in the Claude 5.5 family and the successor to Claude Sonnet 5. Anthropic describes it as its best combination of speed and intelligence. It reads text and images and writes text, with a context window of one million tokens and up to 128K tokens per response.

Like the other current Claude models, Sonnet 5.5 uses adaptive thinking, steered by an effort setting. Thinking is on by default, and the lowest setting skips up-front thinking and only reasons between tool calls. Anthropic gives its reliable knowledge cutoff as June 2026. The weights and parameter count are not published.

What it does well, and where it falls short

Anthropic positions Sonnet 5.5 for code generation, data analysis, writing, visual understanding and agents that call tools. It is strongest at well-scoped tasks: fixing a bug, adding a feature, turning a spreadsheet into a summary, answering questions about a set of documents. Anthropic reports that it needs fewer tokens than Sonnet 5 for the same work.

For work that needs careful judgement over many steps, such as large refactors or complex research, Anthropic points to its Opus models instead. For very high volumes of simple requests, Claude Haiku 5.5 is the cheaper and faster choice. Sonnet 5.5 sits between the two and is a sensible default for most teams.

Calling Claude Sonnet 5.5 through the API

inference.eu speaks the Anthropic Messages format, so the official Anthropic SDKs work once you change the base URL and the key. To use it in Claude Code, set ANTHROPIC_BASE_URL to the inference.eu host, ANTHROPIC_AUTH_TOKEN to your inference.eu key, and choose claude-sonnet-5.5 as the model.

The model is also available through the OpenAI-compatible endpoint, so the OpenAI SDKs, LangChain, LlamaIndex and the Vercel AI SDK work with the model set to claude-sonnet-5.5. Images go in as content parts next to your text. Anthropic advises against setting temperature, top_p or top_k for this model, so leave them out of your requests.

Claude Sonnet 5.5 with data processed in the EU

When you call Claude Sonnet 5.5 on inference.eu, your prompts, images and the model's responses are processed in data centres in the European Union. They are used to answer your request and are never used to train any model.

We sign one data processing agreement under Article 28 of the GDPR with every customer and provide our list of subprocessors, so your data protection officer can see who handles the data and where. The same agreement covers every Claude model and every other model on inference.eu, and everything is billed in euros on one invoice.

claude-sonnet-5.5 · Python
import os
from openai import OpenAI

client = OpenAI(base_url="https://api.inference.eu/v1", api_key=os.environ["INFERENCE_EU_API_KEY"])

response = client.chat.completions.create(
    model="claude-sonnet-5.5",
    messages=[{"role": "user", "content": "Summarise this contract in five bullet points."}],
)
print(response.choices[0].message.content)

What teams use it for

  • 1

    Everyday coding

    Fix bugs, write tests and add features in your editor or in Claude Code, with source code processed in the EU.

  • 2

    Business assistants

    Answer questions about contracts, policies and reports, and draft emails and summaries in English, German, French and other languages.

  • 3

    Agents with tools

    Build agents that search, call your internal APIs and read screenshots, using the tool calling you already use with Claude.

Claude Sonnet 5.5: common questions

The questions buyers, developers and legal teams ask us most. Something missing? Ask us directly.

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