Claude Sonnet 4.6 Now Live on just4o.chat

We’ve added Claude Sonnet 4.6 to just4o.chat — available now for Studio and above.

This is the kind of model upgrade you feel immediately if you use AI like a thinking partner instead of a one-shot autocomplete. Sonnet 4.6 is sharper at staying on task, keeping multi-step threads straight, and reasoning through long, complex requests without losing the plot. Fewer “sure!” moments followed by shallow output. More consistent follow-through.

Why Sonnet 4.6 matters on just4o.chat

Most people don’t need a model that’s “good at benchmarks.” They need a model that:

• reads the whole prompt before answering,

• doesn’t rewrite your intent mid-flight,

• can plan a sequence of steps and actually execute them,

• handles long context without turning foggy or repetitive.

Sonnet 4.6 is meaningfully better at exactly that. It’s stronger at instruction-following, steadier over longer sessions, and less prone to the two classic frustrations: overengineering and “I did it” hallucinations.

Better long-context reasoning (the big upgrade)

Sonnet 4.6 supports a huge context window (up to 1M tokens in beta on Anthropic’s side), but the real win isn’t the number — it’s that the model can reason across large context without collapsing into summaries or ignoring key constraints.

Translation: you can throw more at it in one go (long prompts, big background, multi-part goals) and it’s more likely to:

• keep your constraints intact,

• surface the actual tradeoffs,

• produce an answer that reflects the full request.

“Computer use” improvements (what this means for you)

Anthropic has been pushing hard on “computer use” — models that can navigate software like a human (clicking, typing, handling multi-step flows). Even if you never use a literal “agent that clicks,” the upside shows up as: better procedural reasoning, better step ordering, fewer missing steps, less confusion about UI-like tasks.

Who should use it

If you’re a Studio+ user and you tend to:

• work in threads,

• do multi-step planning,

• iterate on outputs rather than one-and-done…

…Sonnet 4.6 is one of the best “general intelligence” models you can pick right now.

Try it on just4o.chat

If you’re already on Studio or higher, it’s ready. If you’re not, upgrade to Studio to unlock it.

Look up just4o.chat and give Sonnet 4.6 a real test: take one of your messier prompts — the kind that usually causes models to drop requirements — and see how well it holds the thread.