Anthropic’s Claude models on Ai-ChatPro
Ai-ChatPro lets you use Claude, the AI developed by Anthropic, right in your chat, alongside the other major AIs on the market. You'll find 9 Claude models on Ai-ChatPro: Claude Haiku, Claude Sonnet, Claude Opus and Claude Fable. Each has its strengths: speed, writing quality, in-depth reasoning or long-running work.
This page helps you choose the right Claude model for your needs.
What is Claude?
Claude is a conversational artificial intelligence created by Anthropic, an American company specialized in AI research. Like ChatGPT or Gemini, Claude understands your written requests and answers in natural language: it writes, summarizes, translates, analyzes documents, reasons about complex problems and writes code.
Claude is known for the quality of its writing, its ability to follow instructions precisely and to work on long documents without losing the thread. On Ai-ChatPro, you use it without an Anthropic account or a separate subscription.
The 4 Claude model families
Claude models are grouped into families. The higher the tier, the more time the model takes to reason through long, demanding tasks.
- Haiku: the fastest, for simple tasks and instant answers.
- Sonnet: the balance between speed and quality, especially for writing.
- Opus: precision and large volumes, for specialist topics.
- Fable: planning and complex work carried out in several steps.
What can you do with Claude?
- Write articles, emails, LinkedIn posts, product sheets or marketing content with a natural tone.
- Rephrase and proofread a text: spelling, style, register, length.
- Summarize and analyze reports, contracts, minutes or long documents.
- Code: write, explain, debug or review code in most languages.
- Reason about a problem: compare options, structure a decision, prepare a plan.
- Translate texts while keeping the tone and meaning.
Comparison of the Claude models available on Ai-ChatPro
Models are sorted by family: Haiku, Sonnet, Opus, then Fable. Click Use Claude to open the chat directly with the chosen model.
| Model | Description | Best for | |
|---|---|---|---|
| Claude Haiku 4.5 | Answers fast while staying careful and faithful to instructions. | Small writing tasks, proofreading, everyday questions | Use Claude Haiku |
| Claude Sonnet 4.6 | Excellent for writing: respects the requested tone and produces natural texts. | Articles, letters, marketing content, subtle rewording | Use Claude Sonnet |
| Claude Sonnet 5 | Combines responsiveness and sharp reasoning, from simple to elaborate requests. | Writing, analysis, code, thinking | Use Claude Sonnet |
| Claude Sonnet 5.5 | Mixes depth and responsiveness: the natural choice when a request goes beyond the simple, without needing minutes of thinking. | Code, analysis, elaborate writing | Use Claude Sonnet |
| Claude Opus 4.8 | Very comfortable with large volumes, keeps track over long sessions and honestly flags its doubts. | Reports, contracts, entire codebases | Use Claude Opus |
| Claude Opus 5 | For specialist topics that require precision and accuracy: methodical reasoning and highly structured answers. | Finance, legal, technical | Use Claude Opus |
| Claude Opus 5.5 | Built for long, demanding assignments: takes the time to do things right and stays consistent from start to finish. | Complete files, large code projects, in-depth research | Use Claude Opus |
| Claude Fable 5 | Able to plan, break down and check complex work from start to finish. | Advanced studies, software architecture, strategic files | Use Claude Fable |
| Claude Fable 5.1 | Carries out ambitious multi-step work with a high level of reliability. | Code, demanding intellectual work | Use Claude Fable |
Which Claude model should you choose?
- A quick answer: Claude Haiku 4.5, for everyday questions and proofreading.
- Writing a polished text: Claude Sonnet 4.6, for articles, emails and marketing content with a natural tone.
- A good balance for almost everything: Claude Sonnet 5 or Claude Sonnet 5.5, for code, analysis and elaborate writing.
- Analyzing large documents: Claude Opus 4.8, for reports, contracts and large volumes.
- A specialist topic where accuracy matters: Claude Opus 5, for finance, legal and technical topics.
- A long, complex project: Claude Fable 5, Claude Fable 5.1 or Claude Opus 5.5, to plan and carry out work from start to finish.
Still unsure, or maybe Claude isn't the best fit for your needs? Answer 3 questions to find the right AI model.
How do you use Claude on Ai-ChatPro?
- Open the Ai-ChatPro chat. Log in to your Ai-ChatPro space.
- Choose a Claude model. In the model selector at the top of the chat, select Claude Haiku, Sonnet, Opus or Fable.
- Write your request. Write your prompt in the language of your choice, add a document if needed, then send.
- Switch models if needed. You can move to another Claude model, or to another AI, without losing the conversation.
Tip: give Claude the context, the goal and the expected format (length, tone, list or table). The more precise the instruction, the more useful the answer.
Why use Claude on Ai-ChatPro?
- Every Claude model in one place: Haiku, Sonnet, Opus and Fable in a single chat interface.
- Switch models at any time depending on the task, without changing tools.
- Compare with other AIs (GPT, Gemini, Mistral and more) without piling up subscriptions.
- A chat available in every language, for professional and personal use.
Frequently asked questions
What is Claude Opus on Ai-ChatPro?
Claude Opus is Anthropic’s model family for demanding tasks. On Ai-ChatPro, you get Claude Opus 4.8, Claude Opus 5 and Claude Opus 5.5, for large volumes, specialist technical topics and long assignments.
What is the difference between Claude Haiku, Sonnet, Opus and Fable?
Haiku is the fastest and suits simple tasks. Sonnet offers the best balance between speed and quality, especially for writing. Opus is built for precision and large volumes. Fable is designed to plan and carry out complex multi-step work.
In which languages can I use Claude on Ai-ChatPro?
The Ai-ChatPro chat is available in every language. You can write, ask your questions and get your answers in the language of your choice with all the Claude models offered.
Which Claude model should I choose for writing or coding?
For writing, Claude Sonnet 4.6 is an excellent choice. For coding or analysis, Claude Sonnet 5.5 is the all-round option, and Claude Fable 5.1 suits ambitious coding projects.
Do I need an Anthropic account to use Claude?
No. All Claude models are available from your Ai-ChatPro account, with no separate Anthropic account or subscription.