Claude Fable 5.1 and GPT-6 Astra: The Newest AI Models Are Now Live in saldiaBuild

Two new flagship models, one update

Within a single week, Anthropic and OpenAI have both unveiled their new flagship models – and both are now live in saldiaBuild: Claude Fable 5.1, available since 1 September 2026, and GPT-6 Astra, the new model behind ChatGPT, since 4 September 2026. You simply pick which of the two builds your website before you generate.

As with the update to Claude Opus 5: there is nothing to migrate and nothing new to learn. Only the model menu has grown by two entries.

Claude Fable 5.1: the top tier gets sharper

Fable 5.1 is the successor to Claude Fable 5 and remains Anthropic's highest model tier – above Opus 5. Three things matter most for us:

• Considerably stronger on long, multi-step tasks: On agentic coding, Anthropic reports the success rate rising from 42 to around 56 percent (Terminal-Bench 4.0). Building a website – researching, structuring, writing, designing – is exactly that kind of task.
• Better at knowledge work: Anthropic also measures a clear lead over Fable 5 and Opus 5 in writing, structuring and research.
• More efficient to run: Typical workloads are around 25 percent cheaper than with Fable 5, according to Anthropic – at an unchanged list price.

The underlying figures are in Anthropic's official announcement.

GPT-6 Astra: OpenAI's new generation

GPT-6 Astra is OpenAI's first generational leap since GPT-5 – and, since 4 September, the model ChatGPT runs on. OpenAI describes it as faster than any previous version and especially good at staying on task: it sticks to the brief, understands the intent behind it and works through multi-step workflows reliably. In coding and in operating browsers and computers it sets new highs, according to OpenAI.

For saldiaBuild this means that, alongside the Claude models, OpenAI's newest generation is now available as well. If you prefer working with GPT, you get the same performance class as with Anthropic.

What this changes about your website

The strengths of both models lie exactly where website generation is most likely to stumble:

• Coherence across many pages: Navigation, subpages and internal links line up, because the model keeps the whole project in view instead of thinking page by page.
• Revisions in the chat: Change requests are implemented more tightly – what you asked for happens, without three extra things on top.
• Less rework: Both models deliver finished results instead of placeholders you have to fill in later.

The fastest way to find out which of the two suits your project better is to try it – switching is one click, and saldiaBuild works the same either way.

How to use the new models

By default, saldiaBuild continues to build your website with Claude Opus 5. If you want to use Fable 5.1 or GPT-6 Astra, you select the model before generating – the choice applies per project, for the first draft as well as for later revisions. Everything else stays the same: research AI before writing, static technology without a CMS, Swiss hosting included and selling from day one via saldiaPay.

The easiest way to try it is the Free plan: there you create your website with the credits we give you and see for yourself what the new models can do. You'll find all the details on the saldiaBuild product page – and if you have questions, our Swiss support team in Burgdorf is there for you as always.